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AC. The Calendar and the Diary

Emacs provides the functions of a desk calendar, with a diary of planned or past events. It also has facilities for managing your appointments, and keeping track of how much time you spend working on certain projects.

To enter the calendar, type M-x calendar; this displays a three-month calendar centered on the current month, with point on the current date. With a numeric argument, as in C-u M-x calendar, it prompts you for the month and year to be the center of the three-month calendar. The calendar uses its own buffer, whose major mode is Calendar mode.

Mouse-2 in the calendar brings up a menu of operations on a particular date; C-Mouse-3 brings up a menu of commonly used calendar features that are independent of any particular date. To exit the calendar, type q. See section `Calendar' in The Emacs Lisp Reference Manual, for customization information about the calendar and diary.

AC.1 Movement in the Calendar  Moving through the calendar; selecting a date.
AC.2 Scrolling in the Calendar  Bringing earlier or later months onto the screen.
AC.3 Counting Days  How many days are there between two dates?
AC.4 Miscellaneous Calendar Commands  Exiting or recomputing the calendar.
AC.5 LaTeX Calendar  Print a calendar using LaTeX.
AC.6 Holidays  Displaying dates of holidays.
AC.7 Times of Sunrise and Sunset  Displaying local times of sunrise and sunset.
AC.8 Phases of the Moon  Displaying phases of the moon.
AC.9 Conversion To and From Other Calendars  Converting dates to other calendar systems.
AC.10 The Diary  Displaying events from your diary.
AC.11 Appointments  Reminders when it's time to do something.
AC.12 Daylight Savings Time  How to specify when daylight savings time is active.
AC.13 Summing Time Intervals  Keeping track of time intervals.

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AC.1 Movement in the Calendar

Calendar mode lets you move through the calendar in logical units of time such as days, weeks, months, and years. If you move outside the three months originally displayed, the calendar display "scrolls" automatically through time to make the selected date visible. Moving to a date lets you view its holidays or diary entries, or convert it to other calendars; moving longer time periods is also useful simply to scroll the calendar.

AC.1.1 Motion by Standard Lengths of Time  Moving by days, weeks, months, and years.
AC.1.2 Beginning or End of Week, Month or Year  Moving to start/end of weeks, months, and years.
AC.1.3 Specified Dates  Moving to the current date or another specific date.

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AC.1.1 Motion by Standard Lengths of Time

The commands for movement in the calendar buffer parallel the commands for movement in text. You can move forward and backward by days, weeks, months, and years.

Move point one day forward (calendar-forward-day).
Move point one day backward (calendar-backward-day).
Move point one week forward (calendar-forward-week).
Move point one week backward (calendar-backward-week).
Move point one month forward (calendar-forward-month).
Move point one month backward (calendar-backward-month).
C-x ]
Move point one year forward (calendar-forward-year).
C-x [
Move point one year backward (calendar-backward-year).

The day and week commands are natural analogues of the usual Emacs commands for moving by characters and by lines. Just as C-n usually moves to the same column in the following line, in Calendar mode it moves to the same day in the following week. And C-p moves to the same day in the previous week.

The arrow keys are equivalent to C-f, C-b, C-n and C-p, just as they normally are in other modes.

The commands for motion by months and years work like those for weeks, but move a larger distance. The month commands M-} and M-{ move forward or backward by an entire month's time. The year commands C-x ] and C-x [ move forward or backward a whole year.

The easiest way to remember these commands is to consider months and years analogous to paragraphs and pages of text, respectively. But the commands themselves are not quite analogous. The ordinary Emacs paragraph commands move to the beginning or end of a paragraph, whereas these month and year commands move by an entire month or an entire year, which usually involves skipping across the end of a month or year.

All these commands accept a numeric argument as a repeat count. For convenience, the digit keys and the minus sign specify numeric arguments in Calendar mode even without the Meta modifier. For example, 100 C-f moves point 100 days forward from its present location.

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AC.1.2 Beginning or End of Week, Month or Year

A week (or month, or year) is not just a quantity of days; we think of weeks (months, years) as starting on particular dates. So Calendar mode provides commands to move to the beginning or end of a week, month or year:

Move point to start of week (calendar-beginning-of-week).
Move point to end of week (calendar-end-of-week).
Move point to start of month (calendar-beginning-of-month).
Move point to end of month (calendar-end-of-month).
Move point to start of year (calendar-beginning-of-year).
Move point to end of year (calendar-end-of-year).

These commands also take numeric arguments as repeat counts, with the repeat count indicating how many weeks, months, or years to move backward or forward.

By default, weeks begin on Sunday. To make them begin on Monday instead, set the variable calendar-week-start-day to 1.

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AC.1.3 Specified Dates

Calendar mode provides commands for moving to a particular date specified in various ways.

g d
Move point to specified date (calendar-goto-date).
Center calendar around specified month (calendar-other-month).
Move point to today's date (calendar-goto-today).

g d (calendar-goto-date) prompts for a year, a month, and a day of the month, and then moves to that date. Because the calendar includes all dates from the beginning of the current era, you must type the year in its entirety; that is, type `1990', not `90'.

o (calendar-other-month) prompts for a month and year, then centers the three-month calendar around that month.

You can return to today's date with . (calendar-goto-today).

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AC.2 Scrolling in the Calendar

The calendar display scrolls automatically through time when you move out of the visible portion. You can also scroll it manually. Imagine that the calendar window contains a long strip of paper with the months on it. Scrolling the calendar means moving the strip horizontally, so that new months become visible in the window.

C-x <
Scroll calendar one month forward (scroll-calendar-left).
C-x >
Scroll calendar one month backward (scroll-calendar-right).
Scroll calendar three months forward (scroll-calendar-left-three-months).
Scroll calendar three months backward (scroll-calendar-right-three-months).

The most basic calendar scroll commands scroll by one month at a time. This means that there are two months of overlap between the display before the command and the display after. C-x < scrolls the calendar contents one month to the left; that is, it moves the display forward in time. C-x > scrolls the contents to the right, which moves backwards in time.

The commands C-v and M-v scroll the calendar by an entire "screenful"---three months--in analogy with the usual meaning of these commands. C-v makes later dates visible and M-v makes earlier dates visible. These commands take a numeric argument as a repeat count; in particular, since C-u multiplies the next command by four, typing C-u C-v scrolls the calendar forward by a year and typing C-u M-v scrolls the calendar backward by a year.

The function keys NEXT and PRIOR are equivalent to C-v and M-v, just as they are in other modes.

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AC.3 Counting Days

Display the number of days in the current region (calendar-count-days-region).

To determine the number of days in the region, type M-= (calendar-count-days-region). The numbers of days shown is inclusive; that is, it includes the days specified by mark and point.

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AC.4 Miscellaneous Calendar Commands

p d
Display day-in-year (calendar-print-day-of-year).
C-c C-l
Regenerate the calendar window (redraw-calendar).
Scroll the next window (scroll-other-window).
Exit from calendar (exit-calendar).

To display the number of days elapsed since the start of the year, or the number of days remaining in the year, type the p d command (calendar-print-day-of-year). This displays both of those numbers in the echo area. The number of days elapsed includes the selected date. The number of days remaining does not include that date.

If the calendar window text gets corrupted, type C-c C-l (redraw-calendar) to redraw it. (This can only happen if you use non-Calendar-mode editing commands.)

In Calendar mode, you can use SPC (scroll-other-window) to scroll the other window. This is handy when you display a list of holidays or diary entries in another window.

To exit from the calendar, type q (exit-calendar). This buries all buffers related to the calendar, selecting other buffers. (If a frame contains a dedicated calendar window, exiting from the calendar iconifies that frame.)

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AC.5 LaTeX Calendar

The Calendar LaTeX commands produce a buffer of LaTeX code that prints as a calendar. Depending on the command you use, the printed calendar covers the day, week, month or year that point is in.

t m
Generate a one-month calendar (cal-tex-cursor-month).
t M
Generate a sideways-printing one-month calendar (cal-tex-cursor-month-landscape).
t d
Generate a one-day calendar (cal-tex-cursor-day).
t w 1
Generate a one-page calendar for one week (cal-tex-cursor-week).
t w 2
Generate a two-page calendar for one week (cal-tex-cursor-week2).
t w 3
Generate an ISO-style calendar for one week (cal-tex-cursor-week-iso).
t w 4
Generate a calendar for one Monday-starting week (cal-tex-cursor-week-monday).
t f w
Generate a Filofax-style two-weeks-at-a-glance calendar (cal-tex-cursor-filofax-2week).
t f W
Generate a Filofax-style one-week-at-a-glance calendar (cal-tex-cursor-filofax-week).
t y
Generate a calendar for one year (cal-tex-cursor-year).
t Y
Generate a sideways-printing calendar for one year (cal-tex-cursor-year-landscape).
t f y
Generate a Filofax-style calendar for one year (cal-tex-cursor-filofax-year).

Some of these commands print the calendar sideways (in "landscape mode"), so it can be wider than it is long. Some of them use Filofax paper size (3.75in x 6.75in). All of these commands accept a prefix argument which specifies how many days, weeks, months or years to print (starting always with the selected one).

If the variable cal-tex-holidays is non-nil (the default), then the printed calendars show the holidays in calendar-holidays. If the variable cal-tex-diary is non-nil (the default is nil), diary entries are included also (in weekly and monthly calendars only). If the variable cal-tex-rules is non-nil (the default is nil), the calendar displays ruled pages in styles that have sufficient room.

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AC.6 Holidays

The Emacs calendar knows about all major and many minor holidays, and can display them.

Display holidays for the selected date (calendar-cursor-holidays).
Mouse-2 Holidays
Display any holidays for the date you click on.
Mark holidays in the calendar window (mark-calendar-holidays).
Unmark calendar window (calendar-unmark).
List all holidays for the displayed three months in another window (list-calendar-holidays).
M-x holidays
List all holidays for three months around today's date in another window.
M-x list-holidays
List holidays in another window for a specified range of years.

To see if any holidays fall on a given date, position point on that date in the calendar window and use the h command. Alternatively, click on that date with Mouse-2 and then choose Holidays from the menu that appears. Either way, this displays the holidays for that date, in the echo area if they fit there, otherwise in a separate window.

To view the distribution of holidays for all the dates shown in the calendar, use the x command. This displays the dates that are holidays in a different face (or places a `*' after these dates, if display with multiple faces is not available). The command applies both to the currently visible months and to other months that subsequently become visible by scrolling. To turn marking off and erase the current marks, type u, which also erases any diary marks (see section AC.10 The Diary).

To get even more detailed information, use the a command, which displays a separate buffer containing a list of all holidays in the current three-month range. You can use SPC in the calendar window to scroll that list.

The command M-x holidays displays the list of holidays for the current month and the preceding and succeeding months; this works even if you don't have a calendar window. If you want the list of holidays centered around a different month, use C-u M-x holidays, which prompts for the month and year.

The holidays known to Emacs include United States holidays and the major Christian, Jewish, and Islamic holidays; also the solstices and equinoxes.

The command M-x list-holidays displays the list of holidays for a range of years. This function asks you for the starting and stopping years, and allows you to choose all the holidays or one of several categories of holidays. You can use this command even if you don't have a calendar window.

The dates used by Emacs for holidays are based on current practice, not historical fact. Historically, for instance, the start of daylight savings time and even its existence have varied from year to year, but present United States law mandates that daylight savings time begins on the first Sunday in April. When the daylight savings rules are set up for the United States, Emacs always uses the present definition, even though it is wrong for some prior years.

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AC.7 Times of Sunrise and Sunset

Special calendar commands can tell you, to within a minute or two, the times of sunrise and sunset for any date.

Display times of sunrise and sunset for the selected date (calendar-sunrise-sunset).
Mouse-2 Sunrise/sunset
Display times of sunrise and sunset for the date you click on.
M-x sunrise-sunset
Display times of sunrise and sunset for today's date.
C-u M-x sunrise-sunset
Display times of sunrise and sunset for a specified date.

Within the calendar, to display the local times of sunrise and sunset in the echo area, move point to the date you want, and type S. Alternatively, click Mouse-2 on the date, then choose `Sunrise/sunset' from the menu that appears. The command M-x sunrise-sunset is available outside the calendar to display this information for today's date or a specified date. To specify a date other than today, use C-u M-x sunrise-sunset, which prompts for the year, month, and day.

You can display the times of sunrise and sunset for any location and any date with C-u C-u M-x sunrise-sunset. This asks you for a longitude, latitude, number of minutes difference from Coordinated Universal Time, and date, and then tells you the times of sunrise and sunset for that location on that date.

Because the times of sunrise and sunset depend on the location on earth, you need to tell Emacs your latitude, longitude, and location name before using these commands. Here is an example of what to set:

(setq calendar-latitude 40.1)
(setq calendar-longitude -88.2)
(setq calendar-location-name "Urbana, IL")

Use one decimal place in the values of calendar-latitude and calendar-longitude.

Your time zone also affects the local time of sunrise and sunset. Emacs usually gets time zone information from the operating system, but if these values are not what you want (or if the operating system does not supply them), you must set them yourself. Here is an example:

(setq calendar-time-zone -360)
(setq calendar-standard-time-zone-name "CST")
(setq calendar-daylight-time-zone-name "CDT")

The value of calendar-time-zone is the number of minutes difference between your local standard time and Coordinated Universal Time (Greenwich time). The values of calendar-standard-time-zone-name and calendar-daylight-time-zone-name are the abbreviations used in your time zone. Emacs displays the times of sunrise and sunset corrected for daylight savings time. See section AC.12 Daylight Savings Time, for how daylight savings time is determined.

As a user, you might find it convenient to set the calendar location variables for your usual physical location in your `.emacs' file. And when you install Emacs on a machine, you can create a `default.el' file which sets them properly for the typical location of most users of that machine. See section AD.7 The Init File, `~/.emacs'.

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AC.8 Phases of the Moon

These calendar commands display the dates and times of the phases of the moon (new moon, first quarter, full moon, last quarter). This feature is useful for debugging problems that "depend on the phase of the moon."

Display the dates and times for all the quarters of the moon for the three-month period shown (calendar-phases-of-moon).
M-x phases-of-moon
Display dates and times of the quarters of the moon for three months around today's date.

Within the calendar, use the M command to display a separate buffer of the phases of the moon for the current three-month range. The dates and times listed are accurate to within a few minutes.

Outside the calendar, use the command M-x phases-of-moon to display the list of the phases of the moon for the current month and the preceding and succeeding months. For information about a different month, use C-u M-x phases-of-moon, which prompts for the month and year.

The dates and times given for the phases of the moon are given in local time (corrected for daylight savings, when appropriate); but if the variable calendar-time-zone is void, Coordinated Universal Time (the Greenwich time zone) is used. See section AC.12 Daylight Savings Time.

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AC.9 Conversion To and From Other Calendars

The Emacs calendar displayed is always the Gregorian calendar, sometimes called the "new style" calendar, which is used in most of the world today. However, this calendar did not exist before the sixteenth century and was not widely used before the eighteenth century; it did not fully displace the Julian calendar and gain universal acceptance until the early twentieth century. The Emacs calendar can display any month since January, year 1 of the current era, but the calendar displayed is the Gregorian, even for a date at which the Gregorian calendar did not exist.

While Emacs cannot display other calendars, it can convert dates to and from several other calendars.

AC.9.1 Supported Calendar Systems  The calendars Emacs understands
     (aside from Gregorian).
AC.9.2 Converting To Other Calendars  Converting the selected date to various calendars.
AC.9.3 Converting From Other Calendars  Moving to a date specified in another calendar.
AC.9.4 Converting from the Mayan Calendar  Moving to a date specified in a Mayan calendar.

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AC.9.1 Supported Calendar Systems

The ISO commercial calendar is used largely in Europe.

The Julian calendar, named after Julius Caesar, was the one used in Europe throughout medieval times, and in many countries up until the nineteenth century.

Astronomers use a simple counting of days elapsed since noon, Monday, January 1, 4713 B.C. on the Julian calendar. The number of days elapsed is called the Julian day number or the Astronomical day number.

The Hebrew calendar is used by tradition in the Jewish religion. The Emacs calendar program uses the Hebrew calendar to determine the dates of Jewish holidays. Hebrew calendar dates begin and end at sunset.

The Islamic calendar is used in many predominantly Islamic countries. Emacs uses it to determine the dates of Islamic holidays. There is no universal agreement in the Islamic world about the calendar; Emacs uses a widely accepted version, but the precise dates of Islamic holidays often depend on proclamation by religious authorities, not on calculations. As a consequence, the actual dates of observance can vary slightly from the dates computed by Emacs. Islamic calendar dates begin and end at sunset.

The French Revolutionary calendar was created by the Jacobins after the 1789 revolution, to represent a more secular and nature-based view of the annual cycle, and to install a 10-day week in a rationalization measure similar to the metric system. The French government officially abandoned this calendar at the end of 1805.

The Maya of Central America used three separate, overlapping calendar systems, the long count, the tzolkin, and the haab. Emacs knows about all three of these calendars. Experts dispute the exact correlation between the Mayan calendar and our calendar; Emacs uses the Goodman-Martinez-Thompson correlation in its calculations.

The Copts use a calendar based on the ancient Egyptian solar calendar. Their calendar consists of twelve 30-day months followed by an extra five-day period. Once every fourth year they add a leap day to this extra period to make it six days. The Ethiopic calendar is identical in structure, but has different year numbers and month names.

The Persians use a solar calendar based on a design of Omar Khayyam. Their calendar consists of twelve months of which the first six have 31 days, the next five have 30 days, and the last has 29 in ordinary years and 30 in leap years. Leap years occur in a complicated pattern every four or five years.

The Chinese calendar is a complicated system of lunar months arranged into solar years. The years go in cycles of sixty, each year containing either twelve months in an ordinary year or thirteen months in a leap year; each month has either 29 or 30 days. Years, ordinary months, and days are named by combining one of ten "celestial stems" with one of twelve "terrestrial branches" for a total of sixty names that are repeated in a cycle of sixty.

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AC.9.2 Converting To Other Calendars

The following commands describe the selected date (the date at point) in various other calendar systems:

Mouse-2 Other calendars
Display the date that you click on, expressed in various other calendars.
p c
Display ISO commercial calendar equivalent for selected day (calendar-print-iso-date).
p j
Display Julian date for selected day (calendar-print-julian-date).
p a
Display astronomical (Julian) day number for selected day (calendar-print-astro-day-number).
p h
Display Hebrew date for selected day (calendar-print-hebrew-date).
p i
Display Islamic date for selected day (calendar-print-islamic-date).
p f
Display French Revolutionary date for selected day (calendar-print-french-date).
p C
Display Chinese date for selected day (calendar-print-chinese-date).
p k
Display Coptic date for selected day (calendar-print-coptic-date).
p e
Display Ethiopic date for selected day (calendar-print-ethiopic-date).
p p
Display Persian date for selected day (calendar-print-persian-date).
p m
Display Mayan date for selected day (calendar-print-mayan-date).

If you are using X, the easiest way to translate a date into other calendars is to click on it with Mouse-2, then choose Other calendars from the menu that appears. This displays the equivalent forms of the date in all the calendars Emacs understands, in the form of a menu. (Choosing an alternative from this menu doesn't actually do anything--the menu is used only for display.)

Otherwise, move point to the date you want to convert, then type the appropriate command starting with p from the table above. The prefix p is a mnemonic for "print," since Emacs "prints" the equivalent date in the echo area.

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AC.9.3 Converting From Other Calendars

You can use the other supported calendars to specify a date to move to. This section describes the commands for doing this using calendars other than Mayan; for the Mayan calendar, see the following section.

g c
Move to a date specified in the ISO commercial calendar (calendar-goto-iso-date).
g j
Move to a date specified in the Julian calendar (calendar-goto-julian-date).
g a
Move to a date specified with an astronomical (Julian) day number (calendar-goto-astro-day-number).
g h
Move to a date specified in the Hebrew calendar (calendar-goto-hebrew-date).
g i
Move to a date specified in the Islamic calendar (calendar-goto-islamic-date).
g f
Move to a date specified in the French Revolutionary calendar (calendar-goto-french-date).
g C
Move to a date specified in the Chinese calendar (calendar-goto-chinese-date).
g p
Move to a date specified in the Persian calendar (calendar-goto-persian-date).
g k
Move to a date specified in the Coptic calendar (calendar-goto-coptic-date).
g e
Move to a date specified in the Ethiopic calendar (calendar-goto-ethiopic-date).

These commands ask you for a date on the other calendar, move point to the Gregorian calendar date equivalent to that date, and display the other calendar's date in the echo area. Emacs uses strict completion (see section E.3 Completion) whenever it asks you to type a month name, so you don't have to worry about the spelling of Hebrew, Islamic, or French names.

One common question concerning the Hebrew calendar is the computation of the anniversary of a date of death, called a "yahrzeit." The Emacs calendar includes a facility for such calculations. If you are in the calendar, the command M-x list-yahrzeit-dates asks you for a range of years and then displays a list of the yahrzeit dates for those years for the date given by point. If you are not in the calendar, this command first asks you for the date of death and the range of years, and then displays the list of yahrzeit dates.

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AC.9.4 Converting from the Mayan Calendar

Here are the commands to select dates based on the Mayan calendar:

g m l
Move to a date specified by the long count calendar (calendar-goto-mayan-long-count-date).
g m n t
Move to the next occurrence of a place in the tzolkin calendar (calendar-next-tzolkin-date).
g m p t
Move to the previous occurrence of a place in the tzolkin calendar (calendar-previous-tzolkin-date).
g m n h
Move to the next occurrence of a place in the haab calendar (calendar-next-haab-date).
g m p h
Move to the previous occurrence of a place in the haab calendar (calendar-previous-haab-date).
g m n c
Move to the next occurrence of a place in the calendar round (calendar-next-calendar-round-date).
g m p c
Move to the previous occurrence of a place in the calendar round (calendar-previous-calendar-round-date).

To understand these commands, you need to understand the Mayan calendars. The long count is a counting of days with these units:

1 kin = 1 day   1 uinal = 20 kin   1 tun = 18 uinal
1 katun = 20 tun   1 baktun = 20 katun

Thus, the long count date means 12 baktun, 16 katun, 11 tun, 16 uinal, and 6 kin. The Emacs calendar can handle Mayan long count dates as early as, but no earlier. When you use the g m l command, type the Mayan long count date with the baktun, katun, tun, uinal, and kin separated by periods.

The Mayan tzolkin calendar is a cycle of 260 days formed by a pair of independent cycles of 13 and 20 days. Since this cycle repeats endlessly, Emacs provides commands to move backward and forward to the previous or next point in the cycle. Type g m p t to go to the previous tzolkin date; Emacs asks you for a tzolkin date and moves point to the previous occurrence of that date. Similarly, type g m n t to go to the next occurrence of a tzolkin date.

The Mayan haab calendar is a cycle of 365 days arranged as 18 months of 20 days each, followed a 5-day monthless period. Like the tzolkin cycle, this cycle repeats endlessly, and there are commands to move backward and forward to the previous or next point in the cycle. Type g m p h to go to the previous haab date; Emacs asks you for a haab date and moves point to the previous occurrence of that date. Similarly, type g m n h to go to the next occurrence of a haab date.

The Maya also used the combination of the tzolkin date and the haab date. This combination is a cycle of about 52 years called a calendar round. If you type g m p c, Emacs asks you for both a haab and a tzolkin date and then moves point to the previous occurrence of that combination. Use g m n c to move point to the next occurrence of a combination. These commands signal an error if the haab/tzolkin date combination you have typed is impossible.

Emacs uses strict completion (see section E.3.3 Strict Completion) whenever it asks you to type a Mayan name, so you don't have to worry about spelling.

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AC.10 The Diary

The Emacs diary keeps track of appointments or other events on a daily basis, in conjunction with the calendar. To use the diary feature, you must first create a diary file containing a list of events and their dates. Then Emacs can automatically pick out and display the events for today, for the immediate future, or for any specified date.

By default, Emacs uses `~/diary' as the diary file. This is the same file that the calendar utility uses. A sample `~/diary' file is:

12/22/1988  Twentieth wedding anniversary!!
&1/1.       Happy New Year!
10/22       Ruth's birthday.
* 21, *:    Payday
Tuesday--weekly meeting with grad students at 10am
         Supowit, Shen, Bitner, and Kapoor to attend.
1/13/89     Friday the thirteenth!!
&thu 4pm    squash game with Lloyd.
mar 16      Dad's birthday
April 15, 1989 Income tax due.
&* 15       time cards due.

This example uses extra spaces to align the event descriptions of most of the entries. Such formatting is purely a matter of taste.

Although you probably will start by creating a diary manually, Emacs provides a number of commands to let you view, add, and change diary entries.

AC.10.1 Commands Displaying Diary Entries  Viewing diary entries and associated calendar dates.
AC.10.2 The Diary File  Entering events in your diary.
AC.10.3 Date Formats  Various ways you can specify dates.
AC.10.4 Commands to Add to the Diary  Commands to create diary entries.
AC.10.5 Special Diary Entries  Anniversaries, blocks of dates, cyclic entries, etc.

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AC.10.1 Commands Displaying Diary Entries

Once you have created a `~/diary' file, you can use the calendar to view it. You can also view today's events outside of Calendar mode.

Display all diary entries for the selected date (view-diary-entries).
Mouse-2 Diary
Display all diary entries for the date you click on.
Display the entire diary file (show-all-diary-entries).
Mark all visible dates that have diary entries (mark-diary-entries).
Unmark the calendar window (calendar-unmark).
M-x print-diary-entries
Print hard copy of the diary display as it appears.
M-x diary
Display all diary entries for today's date.
M-x diary-mail-entries
Mail yourself email reminders about upcoming diary entries.

Displaying the diary entries with d shows in a separate window the diary entries for the selected date in the calendar. The mode line of the new window shows the date of the diary entries and any holidays that fall on that date. If you specify a numeric argument with d, it shows all the diary entries for that many successive days. Thus, 2 d displays all the entries for the selected date and for the following day.

Another way to display the diary entries for a date is to click Mouse-2 on the date, and then choose Diary entries from the menu that appears.

To get a broader view of which days are mentioned in the diary, use the m command. This displays the dates that have diary entries in a different face (or places a `+' after these dates, if display with multiple faces is not available). The command applies both to the currently visible months and to other months that subsequently become visible by scrolling. To turn marking off and erase the current marks, type u, which also turns off holiday marks (see section AC.6 Holidays).

To see the full diary file, rather than just some of the entries, use the s command.

Display of selected diary entries uses the selective display feature to hide entries that don't apply.

The diary buffer as you see it is an illusion, so simply printing the buffer does not print what you see on your screen. There is a special command to print hard copy of the diary buffer as it appears; this command is M-x print-diary-entries. It sends the data directly to the printer. You can customize it like lpr-region (see section AC.18 Hardcopy Output).

The command M-x diary displays the diary entries for the current date, independently of the calendar display, and optionally for the next few days as well; the variable number-of-diary-entries specifies how many days to include. See section `Calendar' in The Emacs Lisp Reference Manual.

If you put (diary) in your `.emacs' file, this automatically displays a window with the day's diary entries, when you enter Emacs. The mode line of the displayed window shows the date and any holidays that fall on that date.

Many users like to receive notice of events in their diary as email. To send such mail to yourself, use the command M-x diary-mail-entries. A prefix argument specifies how many days (starting with today) to check; otherwise, the variable diary-mail-days says how many days.

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AC.10.2 The Diary File

Your diary file is a file that records events associated with particular dates. The name of the diary file is specified by the variable diary-file; `~/diary' is the default. The calendar utility program supports a subset of the format allowed by the Emacs diary facilities, so you can use that utility to view the diary file, with reasonable results aside from the entries it cannot understand.

Each entry in the diary file describes one event and consists of one or more lines. An entry always begins with a date specification at the left margin. The rest of the entry is simply text to describe the event. If the entry has more than one line, then the lines after the first must begin with whitespace to indicate they continue a previous entry. Lines that do not begin with valid dates and do not continue a preceding entry are ignored.

You can inhibit the marking of certain diary entries in the calendar window; to do this, insert an ampersand (`&') at the beginning of the entry, before the date. This has no effect on display of the entry in the diary window; it affects only marks on dates in the calendar window. Nonmarking entries are especially useful for generic entries that would otherwise mark many different dates.

If the first line of a diary entry consists only of the date or day name with no following blanks or punctuation, then the diary window display doesn't include that line; only the continuation lines appear. For example, this entry:

      Bill B. visits Princeton today
      2pm Cognitive Studies Committee meeting
      2:30-5:30 Liz at Lawrenceville
      4:00pm Dentist appt
      7:30pm Dinner at George's
      8:00-10:00pm concert

appears in the diary window without the date line at the beginning. This style of entry looks neater when you display just a single day's entries, but can cause confusion if you ask for more than one day's entries.

You can edit the diary entries as they appear in the window, but it is important to remember that the buffer displayed contains the entire diary file, with portions of it concealed from view. This means, for instance, that the C-f (forward-char) command can put point at what appears to be the end of the line, but what is in reality the middle of some concealed line.

Be careful when editing the diary entries! Inserting additional lines or adding/deleting characters in the middle of a visible line cannot cause problems, but editing at the end of a line may not do what you expect. Deleting a line may delete other invisible entries that follow it. Before editing the diary, it is best to display the entire file with s (show-all-diary-entries).

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AC.10.3 Date Formats

Here are some sample diary entries, illustrating different ways of formatting a date. The examples all show dates in American order (month, day, year), but Calendar mode supports European order (day, month, year) as an option.

4/20/93  Switch-over to new tabulation system
apr. 25  Start tabulating annual results
4/30  Results for April are due
*/25  Monthly cycle finishes
Friday  Don't leave without backing up files

The first entry appears only once, on April 20, 1993. The second and third appear every year on the specified dates, and the fourth uses a wildcard (asterisk) for the month, so it appears on the 25th of every month. The final entry appears every week on Friday.

You can use just numbers to express a date, as in `month/day' or `month/day/year'. This must be followed by a nondigit. In the date itself, month and day are numbers of one or two digits. The optional year is also a number, and may be abbreviated to the last two digits; that is, you can use `11/12/1989' or `11/12/89'.

Dates can also have the form `monthname day' or `monthname day, year', where the month's name can be spelled in full or abbreviated to three characters (with or without a period). Case is not significant.

A date may be generic; that is, partially unspecified. Then the entry applies to all dates that match the specification. If the date does not contain a year, it is generic and applies to any year. Alternatively, month, day, or year can be a `*'; this matches any month, day, or year, respectively. Thus, a diary entry `3/*/*' matches any day in March of any year; so does `march *'.

If you prefer the European style of writing dates--in which the day comes before the month--type M-x european-calendar while in the calendar, or set the variable european-calendar-style to t before using any calendar or diary command. This mode interprets all dates in the diary in the European manner, and also uses European style for displaying diary dates. (Note that there is no comma after the monthname in the European style.) To go back to the (default) American style of writing dates, type M-x american-calendar.

You can use the name of a day of the week as a generic date which applies to any date falling on that day of the week. You can abbreviate the day of the week to three letters (with or without a period) or spell it in full; case is not significant.

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AC.10.4 Commands to Add to the Diary

While in the calendar, there are several commands to create diary entries:

i d
Add a diary entry for the selected date (insert-diary-entry).
i w
Add a diary entry for the selected day of the week (insert-weekly-diary-entry).
i m
Add a diary entry for the selected day of the month (insert-monthly-diary-entry).
i y
Add a diary entry for the selected day of the year (insert-yearly-diary-entry).

You can make a diary entry for a specific date by selecting that date in the calendar window and typing the i d command. This command displays the end of your diary file in another window and inserts the date; you can then type the rest of the diary entry.

If you want to make a diary entry that applies to a specific day of the week, select that day of the week (any occurrence will do) and type i w. This inserts the day-of-week as a generic date; you can then type the rest of the diary entry. You can make a monthly diary entry in the same fashion: select the day of the month, use the i m command, and type the rest of the entry. Similarly, you can insert a yearly diary entry with the i y command.

All of the above commands make marking diary entries by default. To make a nonmarking diary entry, give a numeric argument to the command. For example, C-u i w makes a nonmarking weekly diary entry.

When you modify the diary file, be sure to save the file before exiting Emacs.

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AC.10.5 Special Diary Entries

In addition to entries based on calendar dates, the diary file can contain sexp entries for regular events such as anniversaries. These entries are based on Lisp expressions (sexps) that Emacs evaluates as it scans the diary file. Instead of a date, a sexp entry contains `%%' followed by a Lisp expression which must begin and end with parentheses. The Lisp expression determines which dates the entry applies to.

Calendar mode provides commands to insert certain commonly used sexp entries:

i a
Add an anniversary diary entry for the selected date (insert-anniversary-diary-entry).
i b
Add a block diary entry for the current region (insert-block-diary-entry).
i c
Add a cyclic diary entry starting at the date (insert-cyclic-diary-entry).

If you want to make a diary entry that applies to the anniversary of a specific date, move point to that date and use the i a command. This displays the end of your diary file in another window and inserts the anniversary description; you can then type the rest of the diary entry. The entry looks like this:

%%(diary-anniversary 10 31 1948) Arthur's birthday

This entry applies to October 31 in any year after 1948; `10 31 1948' specifies the date. (If you are using the European calendar style, the month and day are interchanged.) The reason this expression requires a beginning year is that advanced diary functions can use it to calculate the number of elapsed years.

A block diary entry applies to a specified range of consecutive dates. Here is a block diary entry that applies to all dates from June 24, 1990 through July 10, 1990:

%%(diary-block 6 24 1990 7 10 1990) Vacation

The `6 24 1990' indicates the starting date and the `7 10 1990' indicates the stopping date. (Again, if you are using the European calendar style, the month and day are interchanged.)

To insert a block entry, place point and the mark on the two dates that begin and end the range, and type i b. This command displays the end of your diary file in another window and inserts the block description; you can then type the diary entry.

Cyclic diary entries repeat after a fixed interval of days. To create one, select the starting date and use the i c command. The command prompts for the length of interval, then inserts the entry, which looks like this:

%%(diary-cyclic 50 3 1 1990) Renew medication

This entry applies to March 1, 1990 and every 50th day following; `3 1 1990' specifies the starting date. (If you are using the European calendar style, the month and day are interchanged.)

All three of these commands make marking diary entries. To insert a nonmarking entry, give a numeric argument to the command. For example, C-u i a makes a nonmarking anniversary diary entry.

Marking sexp diary entries in the calendar is extremely time-consuming, since every date visible in the calendar window must be individually checked. So it's a good idea to make sexp diary entries nonmarking (with `&') when possible.

Another sophisticated kind of sexp entry, a floating diary entry, specifies a regularly occurring event by offsets specified in days, weeks, and months. It is comparable to a crontab entry interpreted by the cron utility. Here is a nonmarking, floating diary entry that applies to the last Thursday in November:

&%%(diary-float 11 4 -1) American Thanksgiving

The 11 specifies November (the eleventh month), the 4 specifies Thursday (the fourth day of the week, where Sunday is numbered zero), and the -1 specifies "last" (1 would mean "first," 2 would mean "second," -2 would mean "second-to-last," and so on). The month can be a single month or a list of months. Thus you could change the 11 above to `'(1 2 3)' and have the entry apply to the last Thursday of January, February, and March. If the month is t, the entry applies to all months of the year.

Most generally, sexp diary entries can perform arbitrary computations to determine when they apply. See section `Sexp Diary Entries' in The Emacs Lisp Reference Manual.

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AC.11 Appointments

If you have a diary entry for an appointment, and that diary entry begins with a recognizable time of day, Emacs can warn you several minutes beforehand that that appointment is pending. Emacs alerts you to the appointment by displaying a message in the mode line.

To enable appointment notification, you must enable the time display feature of Emacs, M-x display-time (see section B.3 The Mode Line). You must also add the function appt-make-list to the diary-hook, like this:

(add-hook 'diary-hook 'appt-make-list)

Adding this text to your `.emacs' file does the whole job:

(add-hook 'diary-hook 'appt-make-list)
(diary 0)

With these preparations done, when you display the diary (either with the d command in the calendar window or with the M-x diary command), it sets up an appointment list of all the diary entries found with recognizable times of day, and reminds you just before each of them.

For example, suppose the diary file contains these lines:

  9:30am Coffee break
 12:00pm Lunch

Then on Mondays, after you have displayed the diary, you will be reminded at 9:20am about your coffee break and at 11:50am about lunch.

You can write times in am/pm style (with `12:00am' standing for midnight and `12:00pm' standing for noon), or 24-hour European/military style. You need not be consistent; your diary file can have a mixture of the two styles.

Emacs updates the appointments list automatically just after midnight. This also displays the next day's diary entries in the diary buffer, unless you set appt-display-diary to nil.

You can also use the appointment notification facility like an alarm clock. The command M-x appt-add adds entries to the appointment list without affecting your diary file. You delete entries from the appointment list with M-x appt-delete.

You can turn off the appointment notification feature at any time by setting appt-issue-message to nil.

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AC.12 Daylight Savings Time

Emacs understands the difference between standard time and daylight savings time--the times given for sunrise, sunset, solstices, equinoxes, and the phases of the moon take that into account. The rules for daylight savings time vary from place to place and have also varied historically from year to year. To do the job properly, Emacs needs to know which rules to use.

Some operating systems keep track of the rules that apply to the place where you are; on these systems, Emacs gets the information it needs from the system automatically. If some or all of this information is missing, Emacs fills in the gaps with the rules currently used in Cambridge, Massachusetts. If the resulting rules are not what you want, you can tell Emacs the rules to use by setting certain variables: calendar-daylight-savings-starts and calendar-daylight-savings-ends.

These values should be Lisp expressions that refer to the variable year, and evaluate to the Gregorian date on which daylight savings time starts or (respectively) ends, in the form of a list (month day year). The values should be nil if your area does not use daylight savings time.

Emacs uses these expressions to determine the starting date of daylight savings time for the holiday list and for correcting times of day in the solar and lunar calculations.

The values for Cambridge, Massachusetts are as follows:

(calendar-nth-named-day 1 0 4 year)
(calendar-nth-named-day -1 0 10 year)

That is, the first 0th day (Sunday) of the fourth month (April) in the year specified by year, and the last Sunday of the tenth month (October) of that year. If daylight savings time were changed to start on October 1, you would set calendar-daylight-savings-starts to this:

(list 10 1 year)

If there is no daylight savings time at your location, or if you want all times in standard time, set calendar-daylight-savings-starts and calendar-daylight-savings-ends to nil.

The variable calendar-daylight-time-offset specifies the difference between daylight savings time and standard time, measured in minutes. The value for Cambridge, Massachusetts is 60.

The two variables calendar-daylight-savings-starts-time and calendar-daylight-savings-ends-time specify the number of minutes after midnight local time when the transition to and from daylight savings time should occur. For Cambridge, Massachusetts both variables' values are 120.

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AC.13 Summing Time Intervals

The timeclock feature adds up time intervals, so you can (for instance) keep track of how much time you spend working.

Use the M-x timeclock-in command when you start working on a project, and M-x timeclock-out command when you're done. Each time you do this, it adds one time interval to the record of the project.

Once you've collected data from a number of time intervals, you can use M-x timeclock-workday-remaining to see how much time is left to work today (assuming a typical average of 8 hours a day), and M-x timeclock-when-to-leave which will calculate when you're "done."

If you want Emacs to display the amount of time "left" of your workday in the mode line, either customize the timeclock-modeline-display variable and set its value to t, or invoke the M-x timeclock-modeline-display command.

Terminating the current Emacs session might or might not mean that you have stopped working on the project. If you'd like Emacs to ask you about this, set the value of the variable timeclock-ask-before-exiting to t (via M-x customize). By default, only an explicit M-x timeclock-out tells Emacs that the current interval is over.

The timeclock functions work by accumulating the data in a file called `.timelog' in your home directory. (On MS-DOS, this file is called `_timelog', since an initial period is not allowed in file names on MS-DOS.) You can specify a different name for this file by customizing the variable timeclock-file. If you edit the timeclock file manually, or if you change the value of any of timeclock's customizable variables, you should run the command M-x timeclock-reread-log to update the data in Emacs from the file.

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AC.14 Gnus

Gnus is an Emacs package primarily designed for reading and posting Usenet news. It can also be used to read and respond to messages from a number of other sources--mail, remote directories, digests, and so on.

Here we introduce Gnus and describe several basic features. For full details, see section `Top' in The Gnus Manual.

To start Gnus, type M-x gnus RET.

AC.14.1 Gnus Buffers  The group, summary, and article buffers.
AC.14.2 When Gnus Starts Up  What you should know about starting Gnus.
AC.14.3 Summary of Gnus Commands  A short description of the basic Gnus commands.

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AC.14.1 Gnus Buffers

As opposed to most normal Emacs packages, Gnus uses a number of different buffers to display information and to receive commands. The three buffers users spend most of their time in are the group buffer, the summary buffer and the article buffer.

The group buffer contains a list of groups. This is the first buffer Gnus displays when it starts up. It normally displays only the groups to which you subscribe and that contain unread articles. Use this buffer to select a specific group.

The summary buffer lists one line for each article in a single group. By default, the author, the subject and the line number are displayed for each article, but this is customizable, like most aspects of Gnus display. The summary buffer is created when you select a group in the group buffer, and is killed when you exit the group. Use this buffer to select an article.

The article buffer displays the article. In normal Gnus usage, you don't select this buffer--all useful article-oriented commands work in the summary buffer. But you can select the article buffer, and execute all Gnus commands from that buffer, if you want to.

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AC.14.2 When Gnus Starts Up

At startup, Gnus reads your `.newsrc' news initialization file and attempts to communicate with the local news server, which is a repository of news articles. The news server need not be the same computer you are logged in on.

If you start Gnus and connect to the server, but do not see any newsgroups listed in the group buffer, type L or A k to get a listing of all the groups. Then type u to toggle subscription to groups.

The first time you start Gnus, Gnus subscribes you to a few selected groups. All other groups start out as killed groups for you; you can list them with A k. All new groups that subsequently come to exist at the news server become zombie groups for you; type A z to list them. You can subscribe to a group shown in these lists using the u command.

When you quit Gnus with q, it automatically records in your `.newsrc' and `.newsrc.eld' initialization files the subscribed or unsubscribed status of all groups. You should normally not edit these files manually, but you may if you know how.

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AC.14.3 Summary of Gnus Commands

Reading news is a two-step process:

  1. Choose a group in the group buffer.

  2. Select articles from the summary buffer. Each article selected is displayed in the article buffer in a large window, below the summary buffer in its small window.

Each Gnus buffer has its own special commands; however, the meanings of any given key in the various Gnus buffers are usually analogous, even if not identical. Here are commands for the group and summary buffers:

In the group buffer, update your `.newsrc' initialization file and quit Gnus.

In the summary buffer, exit the current group and return to the group buffer. Thus, typing q twice quits Gnus.

In the group buffer, list all the groups available on your news server (except those you have killed). This may be a long list!

In the group buffer, list only the groups to which you subscribe and which contain unread articles.

In the group buffer, unsubscribe from (or subscribe to) the group listed in the line that point is on. When you quit Gnus by typing q, Gnus lists in your `.newsrc' file which groups you have subscribed to. The next time you start Gnus, you won't see this group, because Gnus normally displays only subscribed-to groups.

In the group buffer, "kill" the current line's group--don't even list it in `.newsrc' from now on. This affects future Gnus sessions as well as the present session.

When you quit Gnus by typing q, Gnus writes information in the file `.newsrc' describing all newsgroups except those you have "killed."

In the group buffer, select the group on the line under the cursor and display the first unread article in that group.

In the summary buffer,

  • Select the article on the line under the cursor if none is selected.

  • Scroll the text of the selected article (if there is one).

  • Select the next unread article if at the end of the current article.

Thus, you can move through all the articles by repeatedly typing SPC.

In the group buffer, move point to the previous group containing unread articles.

In the summary buffer, scroll the text of the article backwards.

Move point to the next unread group, or select the next unread article.

Move point to the previous unread group, or select the previous unread article.

Move point to the next or previous item, even if it is marked as read. This does not select the article or group on that line.

In the summary buffer, do an incremental search of the current text in the article buffer, just as if you switched to the article buffer and typed C-s.

M-s regexp RET
In the summary buffer, search forward for articles containing a match for regexp.

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AC.15 Running Shell Commands from Emacs

Emacs has commands for passing single command lines to inferior shell processes; it can also run a shell interactively with input and output to an Emacs buffer named `*shell*' or run a shell inside a terminal emulator window.

There is a shell implemented entirely in Emacs, documented in a separate manual. See section `Eshell' in Eshell: The Emacs Shell.

M-! cmd RET
Run the shell command line cmd and display the output (shell-command).
M-| cmd RET
Run the shell command line cmd with region contents as input; optionally replace the region with the output (shell-command-on-region).
M-x shell
Run a subshell with input and output through an Emacs buffer. You can then give commands interactively.
M-x term
Run a subshell with input and output through an Emacs buffer. You can then give commands interactively. Full terminal emulation is available.
M-x eshell
Start the Emacs shell.

AC.15.1 Single Shell Commands  How to run one shell command and return.
AC.15.2 Interactive Inferior Shell  Permanent shell taking input via Emacs.
AC.15.3 Shell Mode  Special Emacs commands used with permanent shell.
AC.15.4 Shell Command History  Repeating previous commands in a shell buffer.
AC.15.5 Directory Tracking  Keeping track when the subshell changes directory.
AC.15.6 Shell Mode Options  Options for customizing Shell mode.
AC.15.7 Emacs Terminal Emulator  An Emacs window as a terminal emulator.
AC.15.8 Term Mode  Special Emacs commands used in Term mode.
AC.15.9 Page-At-A-Time Output  Paging in the terminal emulator.
AC.15.10 Remote Host Shell  Connecting to another computer.

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AC.15.1 Single Shell Commands

M-! (shell-command) reads a line of text using the minibuffer and executes it as a shell command in a subshell made just for that command. Standard input for the command comes from the null device. If the shell command produces any output, the output appears either in the echo area (if it is short), or in an Emacs buffer named `*Shell Command Output*', which is displayed in another window but not selected (if the output is long).

For instance, one way to decompress a file `foo.gz' from Emacs is to type M-! gunzip foo.gz RET. That shell command normally creates the file `foo' and produces no terminal output.

A numeric argument, as in M-1 M-!, says to insert terminal output into the current buffer instead of a separate buffer. It puts point before the output, and sets the mark after the output. For instance, M-1 M-! gunzip < foo.gz RET would insert the uncompressed equivalent of `foo.gz' into the current buffer.

If the shell command line ends in `&', it runs asynchronously. For a synchronous shell command, shell-command returns the command's exit status (0 means success), when it is called from a Lisp program. You do not get any status information for an asynchronous command, since it hasn't finished yet.

M-| (shell-command-on-region) is like M-! but passes the contents of the region as the standard input to the shell command, instead of no input. If a numeric argument is used, meaning insert the output in the current buffer, then the old region is deleted first and the output replaces it as the contents of the region. It returns the command's exit status when it is called from a Lisp program.

One use for M-| is to run uudecode. For instance, if the buffer contains uuencoded text, type C-x h M-| uudecode RET to feed the entire buffer contents to the uudecode program. That program will ignore everything except the encoded text, and will store the decoded output into the file whose name is specified in the encoded text.

Both M-! and M-| use shell-file-name to specify the shell to use. This variable is initialized based on your SHELL environment variable when Emacs is started. If the file name does not specify a directory, the directories in the list exec-path are searched; this list is initialized based on the environment variable PATH when Emacs is started. Your `.emacs' file can override either or both of these default initializations.

Both M-! and M-| wait for the shell command to complete. To stop waiting, type C-g to quit; that terminates the shell command with the signal SIGINT---the same signal that C-c normally generates in the shell. Emacs waits until the command actually terminates. If the shell command doesn't stop (because it ignores the SIGINT signal), type C-g again; this sends the command a SIGKILL signal which is impossible to ignore.

To specify a coding system for M-! or M-|, use the command C-x RET c immediately beforehand. See section Q.9 Specifying a Coding System.

Error output from the command is normally intermixed with the regular output. If you set the variable shell-command-default-error-buffer to a string, which is a buffer name, error output is inserted before point in the buffer of that name.

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AC.15.2 Interactive Inferior Shell

To run a subshell interactively, putting its typescript in an Emacs buffer, use M-x shell. This creates (or reuses) a buffer named `*shell*' and runs a subshell with input coming from and output going to that buffer. That is to say, any "terminal output" from the subshell goes into the buffer, advancing point, and any "terminal input" for the subshell comes from text in the buffer. To give input to the subshell, go to the end of the buffer and type the input, terminated by RET.

Emacs does not wait for the subshell to do anything. You can switch windows or buffers and edit them while the shell is waiting, or while it is running a command. Output from the subshell waits until Emacs has time to process it; this happens whenever Emacs is waiting for keyboard input or for time to elapse.

Input lines, once you submit them, are displayed using the face comint-highlight-input, and prompts are displayed using the face comint-highlight-prompt. This makes it easier to see previous input lines in the buffer. See section J.1 Using Multiple Typefaces.

To make multiple subshells, you can invoke M-x shell with a prefix argument (e.g. C-u M-x shell), which will read a buffer name and create (or reuse) a subshell in that buffer. You can also rename the `*shell*' buffer using M-x rename-uniquely, then create a new `*shell*' buffer using plain M-x shell. All the subshells in different buffers run independently and in parallel.

The file name used to load the subshell is the value of the variable explicit-shell-file-name, if that is non-nil. Otherwise, the environment variable ESHELL is used, or the environment variable SHELL if there is no ESHELL. If the file name specified is relative, the directories in the list exec-path are searched; this list is initialized based on the environment variable PATH when Emacs is started. Your `.emacs' file can override either or both of these default initializations.

Emacs sends the new shell the contents of the file `~/.emacs_shellname' as input, if it exists, where shellname is the name of the file that the shell was loaded from. For example, if you use bash, the file sent to it is `~/.emacs_bash'.

To specify a coding system for the shell, you can use the command C-x RET c immediately before M-x shell. You can also specify a coding system after starting the shell by using C-x RET p in the shell buffer. See section Q.9 Specifying a Coding System.

Unless the environment variable EMACS is already defined, Emacs defines it in the subshell, with value t. A shell script can check this variable to determine whether it has been run from an Emacs subshell.

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AC.15.3 Shell Mode

Shell buffers use Shell mode, which defines several special keys attached to the C-c prefix. They are chosen to resemble the usual editing and job control characters present in shells that are not under Emacs, except that you must type C-c first. Here is a complete list of the special key bindings of Shell mode:

At end of buffer send line as input; otherwise, copy current line to end of buffer and send it (comint-send-input). When a line is copied, any prompt at the beginning of the line (text output by programs preceding your input) is omitted. (See also the variable comint-use-prompt-regexp-instead-of-fields.)

Complete the command name or file name before point in the shell buffer (comint-dynamic-complete). TAB also completes history references (see section AC.15.4.3 Shell History References) and environment variable names.

The variable shell-completion-fignore specifies a list of file name extensions to ignore in Shell mode completion. The default setting is nil, but some users prefer ("~" "#" "%") to ignore file names ending in `~', `#' or `%'. Other related Comint modes use the variable comint-completion-fignore instead.

Display temporarily a list of the possible completions of the file name before point in the shell buffer (comint-dynamic-list-filename-completions).

Either delete a character or send EOF (comint-delchar-or-maybe-eof). Typed at the end of the shell buffer, C-d sends EOF to the subshell. Typed at any other position in the buffer, C-d deletes a character as usual.

C-c C-a
Move to the beginning of the line, but after the prompt if any (comint-bol-or-process-mark). If you repeat this command twice in a row, the second time it moves back to the process mark, which is the beginning of the input that you have not yet sent to the subshell. (Normally that is the same place--the end of the prompt on this line--but after C-c SPC the process mark may be in a previous line.)

Accumulate multiple lines of input, then send them together. This command inserts a newline before point, but does not send the preceding text as input to the subshell--at least, not yet. Both lines, the one before this newline and the one after, will be sent together (along with the newline that separates them), when you type RET.

C-c C-u
Kill all text pending at end of buffer to be sent as input (comint-kill-input).

C-c C-w
Kill a word before point (backward-kill-word).

C-c C-c
Interrupt the shell or its current subjob if any (comint-interrupt-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-z
Stop the shell or its current subjob if any (comint-stop-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-\
Send quit signal to the shell or its current subjob if any (comint-quit-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-o
Delete the last batch of output from a shell command (comint-delete-output). This is useful if a shell command spews out lots of output that just gets in the way. This command used to be called comint-kill-output.

C-c C-s
Write the last batch of output from a shell command to a file (comint-write-output). With a prefix argument, the file is appended to instead. Any prompt at the end of the output is not written.

C-c C-r
Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (comint-show-output).

C-c C-e
Scroll to put the end of the buffer at the bottom of the window (comint-show-maximum-output).

C-c C-f
Move forward across one shell command, but not beyond the current line (shell-forward-command). The variable shell-command-regexp specifies how to recognize the end of a command.

C-c C-b
Move backward across one shell command, but not beyond the current line (shell-backward-command).

C-c C-l
Display the buffer's history of shell commands in another window (comint-dynamic-list-input-ring).

M-x dirs
Ask the shell what its current directory is, so that Emacs can agree with the shell.

M-x send-invisible RET text RET
Send text as input to the shell, after reading it without echoing. This is useful when a shell command runs a program that asks for a password.

Alternatively, you can arrange for Emacs to notice password prompts and turn off echoing for them, as follows:

(add-hook 'comint-output-filter-functions

M-x comint-continue-subjob
Continue the shell process. This is useful if you accidentally suspend the shell process.(14)

M-x comint-strip-ctrl-m
Discard all control-M characters from the current group of shell output. The most convenient way to use this command is to make it run automatically when you get output from the subshell. To do that, evaluate this Lisp expression:

(add-hook 'comint-output-filter-functions

M-x comint-truncate-buffer
This command truncates the shell buffer to a certain maximum number of lines, specified by the variable comint-buffer-maximum-size. Here's how to do this automatically each time you get output from the subshell:

(add-hook 'comint-output-filter-functions

Shell mode also customizes the paragraph commands so that only shell prompts start new paragraphs. Thus, a paragraph consists of an input command plus the output that follows it in the buffer.

Shell mode is a derivative of Comint mode, a general-purpose mode for communicating with interactive subprocesses. Most of the features of Shell mode actually come from Comint mode, as you can see from the command names listed above. The special features of Shell mode include the directory tracking feature, and a few user commands.

Other Emacs features that use variants of Comint mode include GUD (see section V.5 Running Debuggers Under Emacs) and M-x run-lisp (see section V.10 Running an External Lisp).

You can use M-x comint-run to execute any program of your choice in a subprocess using unmodified Comint mode--without the specializations of Shell mode.

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AC.15.4 Shell Command History

Shell buffers support three ways of repeating earlier commands. You can use the same keys used in the minibuffer; these work much as they do in the minibuffer, inserting text from prior commands while point remains always at the end of the buffer. You can move through the buffer to previous inputs in their original place, then resubmit them or copy them to the end. Or you can use a `!'-style history reference.

AC.15.4.1 Shell History Ring  Fetching commands from the history list.
AC.15.4.2 Shell History Copying  Moving to a command and then copying it.
AC.15.4.3 Shell History References  Expanding `!'-style history references.

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AC.15.4.1 Shell History Ring

Fetch the next earlier old shell command.

Fetch the next later old shell command.

M-r regexp RET
M-s regexp RET
Search backwards or forwards for old shell commands that match regexp.

C-c C-x (Shell mode)
Fetch the next subsequent command from the history.

Shell buffers provide a history of previously entered shell commands. To reuse shell commands from the history, use the editing commands M-p, M-n, M-r and M-s. These work just like the minibuffer history commands except that they operate on the text at the end of the shell buffer, where you would normally insert text to send to the shell.

M-p fetches an earlier shell command to the end of the shell buffer. Successive use of M-p fetches successively earlier shell commands, each replacing any text that was already present as potential shell input. M-n does likewise except that it finds successively more recent shell commands from the buffer.

The history search commands M-r and M-s read a regular expression and search through the history for a matching command. Aside from the choice of which command to fetch, they work just like M-p and M-n. If you enter an empty regexp, these commands reuse the same regexp used last time.

When you find the previous input you want, you can resubmit it by typing RET, or you can edit it first and then resubmit it if you wish.

Often it is useful to reexecute several successive shell commands that were previously executed in sequence. To do this, first find and reexecute the first command of the sequence. Then type C-c C-x; that will fetch the following command--the one that follows the command you just repeated. Then type RET to reexecute this command. You can reexecute several successive commands by typing C-c C-x RET over and over.

These commands get the text of previous shell commands from a special history list, not from the shell buffer itself. Thus, editing the shell buffer, or even killing large parts of it, does not affect the history that these commands access.

Some shells store their command histories in files so that you can refer to previous commands from previous shell sessions. Emacs reads the command history file for your chosen shell, to initialize its own command history. The file name is `~/.bash_history' for bash, `~/.sh_history' for ksh, and `~/.history' for other shells.

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AC.15.4.2 Shell History Copying

C-c C-p
Move point to the previous prompt (comint-previous-prompt).

C-c C-n
Move point to the following prompt (comint-next-prompt).

Copy the input command which point is in, inserting the copy at the end of the buffer (comint-copy-old-input). This is useful if you move point back to a previous command. After you copy the command, you can submit the copy as input with RET. If you wish, you can edit the copy before resubmitting it.

Moving to a previous input and then copying it with C-c RET produces the same results--the same buffer contents--that you would get by using M-p enough times to fetch that previous input from the history list. However, C-c RET copies the text from the buffer, which can be different from what is in the history list if you edit the input text in the buffer after it has been sent.

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AC.15.4.3 Shell History References

Various shells including csh and bash support history references that begin with `!' and `^'. Shell mode recognizes these constructs, and can perform the history substitution for you.

If you insert a history reference and type TAB, this searches the input history for a matching command, performs substitution if necessary, and places the result in the buffer in place of the history reference. For example, you can fetch the most recent command beginning with `mv' with ! m v TAB. You can edit the command if you wish, and then resubmit the command to the shell by typing RET.

Shell mode can optionally expand history references in the buffer when you send them to the shell. To request this, set the variable comint-input-autoexpand to input. You can make SPC perform history expansion by binding SPC to the command comint-magic-space.

Shell mode recognizes history references when they follow a prompt. Normally, any text output by a program at the beginning of an input line is considered a prompt. However, if the variable comint-use-prompt-regexp-instead-of-fields is non-nil, then Comint mode uses a regular expression to recognize prompts. In general, the variable comint-prompt-regexp specifies the regular expression; Shell mode uses the variable shell-prompt-pattern to set up comint-prompt-regexp in the shell buffer.

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AC.15.5 Directory Tracking

Shell mode keeps track of `cd', `pushd' and `popd' commands given to the inferior shell, so it can keep the `*shell*' buffer's default directory the same as the shell's working directory. It recognizes these commands syntactically, by examining lines of input that are sent.

If you use aliases for these commands, you can tell Emacs to recognize them also. For example, if the value of the variable shell-pushd-regexp matches the beginning of a shell command line, that line is regarded as a pushd command. Change this variable when you add aliases for `pushd'. Likewise, shell-popd-regexp and shell-cd-regexp are used to recognize commands with the meaning of `popd' and `cd'. These commands are recognized only at the beginning of a shell command line.

If Emacs gets confused about changes in the current directory of the subshell, use the command M-x dirs to ask the shell what its current directory is. This command works for shells that support the most common command syntax; it may not work for unusual shells.

You can also use M-x dirtrack-mode to enable (or disable) an alternative and more aggressive method of tracking changes in the current directory.

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AC.15.6 Shell Mode Options

If the variable comint-scroll-to-bottom-on-input is non-nil, insertion and yank commands scroll the selected window to the bottom before inserting.

If comint-scroll-show-maximum-output is non-nil, then scrolling due to the arrival of output tries to place the last line of text at the bottom line of the window, so as to show as much useful text as possible. (This mimics the scrolling behavior of many terminals.) The default is nil.

By setting comint-scroll-to-bottom-on-output, you can opt for having point jump to the end of the buffer whenever output arrives--no matter where in the buffer point was before. If the value is this, point jumps in the selected window. If the value is all, point jumps in each window that shows the Comint buffer. If the value is other, point jumps in all nonselected windows that show the current buffer. The default value is nil, which means point does not jump to the end.

The variable comint-input-ignoredups controls whether successive identical inputs are stored in the input history. A non-nil value means to omit an input that is the same as the previous input. The default is nil, which means to store each input even if it is equal to the previous input.

Three variables customize file name completion. The variable comint-completion-addsuffix controls whether completion inserts a space or a slash to indicate a fully completed file or directory name (non-nil means do insert a space or slash). comint-completion-recexact, if non-nil, directs TAB to choose the shortest possible completion if the usual Emacs completion algorithm cannot add even a single character. comint-completion-autolist, if non-nil, says to list all the possible completions whenever completion is not exact.

Command completion normally considers only executable files. If you set shell-completion-execonly to nil, it considers nonexecutable files as well.

You can configure the behavior of `pushd'. Variables control whether `pushd' behaves like `cd' if no argument is given (shell-pushd-tohome), pop rather than rotate with a numeric argument (shell-pushd-dextract), and only add directories to the directory stack if they are not already on it (shell-pushd-dunique). The values you choose should match the underlying shell, of course.

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AC.15.7 Emacs Terminal Emulator

To run a subshell in a terminal emulator, putting its typescript in an Emacs buffer, use M-x term. This creates (or reuses) a buffer named `*terminal*', and runs a subshell with input coming from your keyboard, and output going to that buffer.

The terminal emulator uses Term mode, which has two input modes. In line mode, Term basically acts like Shell mode; see AC.15.3 Shell Mode.

In char mode, each character is sent directly to the inferior subshell, as "terminal input." Any "echoing" of your input is the responsibility of the subshell. The sole exception is the terminal escape character, which by default is C-c (see section AC.15.8 Term Mode). Any "terminal output" from the subshell goes into the buffer, advancing point.

Some programs (such as Emacs itself) need to control the appearance on the terminal screen in detail. They do this by sending special control codes. The exact control codes needed vary from terminal to terminal, but nowadays most terminals and terminal emulators (including xterm) understand the ANSI-standard (VT100-style) escape sequences. Term mode recognizes these escape sequences, and handles each one appropriately, changing the buffer so that the appearance of the window matches what it would be on a real terminal. You can actually run Emacs inside an Emacs Term window.

The file name used to load the subshell is determined the same way as for Shell mode. To make multiple terminal emulators, rename the buffer `*terminal*' to something different using M-x rename-uniquely, just as with Shell mode.

Unlike Shell mode, Term mode does not track the current directory by examining your input. But some shells can tell Term what the current directory is. This is done automatically by bash version 1.15 and later.

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AC.15.8 Term Mode

The terminal emulator uses Term mode, which has two input modes. In line mode, Term basically acts like Shell mode; see AC.15.3 Shell Mode. In char mode, each character is sent directly to the inferior subshell, except for the Term escape character, normally C-c.

To switch between line and char mode, use these commands:

C-c C-k
Switch to line mode. Do nothing if already in line mode.

C-c C-j
Switch to char mode. Do nothing if already in char mode.

The following commands are only available in char mode:

C-c C-c
Send a literal C-c to the sub-shell.

C-c C-x
A prefix command to access the global C-x commands conveniently. For example, C-c C-x o invokes the global binding of C-x o, which is normally `other-window'.

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AC.15.9 Page-At-A-Time Output

Term mode has a page-at-a-time feature. When enabled it makes output pause at the end of each screenful.

C-c C-q
Toggle the page-at-a-time feature. This command works in both line and char modes. When page-at-a-time is enabled, the mode-line displays the word `page'.

With page-at-a-time enabled, whenever Term receives more than a screenful of output since your last input, it pauses, displaying `**MORE**' in the mode-line. Type SPC to display the next screenful of output. Type ? to see your other options. The interface is similar to the more program.

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AC.15.10 Remote Host Shell

You can login to a remote computer, using whatever commands you would from a regular terminal (e.g. using the telnet or rlogin commands), from a Term window.

A program that asks you for a password will normally suppress echoing of the password, so the password will not show up in the buffer. This will happen just as if you were using a real terminal, if the buffer is in char mode. If it is in line mode, the password is temporarily visible, but will be erased when you hit return. (This happens automatically; there is no special password processing.)

When you log in to a different machine, you need to specify the type of terminal you're using. Terminal types `ansi' or `vt100' will work on most systems.

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AC.16 Using Emacs as a Server

Various programs such as mail can invoke your choice of editor to edit a particular piece of text, such as a message that you are sending. By convention, most of these programs use the environment variable EDITOR to specify which editor to run. If you set EDITOR to `emacs', they invoke Emacs--but in an inconvenient fashion, by starting a new, separate Emacs process. This is inconvenient because it takes time and because the new Emacs process doesn't share the buffers in any existing Emacs process.

You can arrange to use your existing Emacs process as the editor for programs like mail by using the Emacs client and Emacs server programs. Here is how.

First, the preparation. Within Emacs, call the function server-start. (Your `.emacs' file can do this automatically if you add the expression (server-start) to it.) Then, outside Emacs, set the EDITOR environment variable to `emacsclient'. (Note that some programs use a different environment variable; for example, to make TeX use `emacsclient', you should set the TEXEDIT environment variable to `emacsclient +%d %s'.)

Then, whenever any program invokes your specified EDITOR program, the effect is to send a message to your principal Emacs telling it to visit a file. (That's what the program emacsclient does.) Emacs displays the buffer immediately and you can immediately begin editing it.

When you've finished editing that buffer, type C-x # (server-edit). This saves the file and sends a message back to the emacsclient program telling it to exit. The programs that use EDITOR wait for the "editor" (actually, emacsclient) to exit. C-x # also checks for other pending external requests to edit various files, and selects the next such file.

You can switch to a server buffer manually if you wish; you don't have to arrive at it with C-x #. But C-x # is the way to say that you are finished with one.

Finishing with a server buffer also kills the buffer, unless it already existed in the Emacs session before the server asked to create it. However, if you set server-kill-new-buffers to nil, then a different criterion is used: finishing with a server buffer kills it if the file name matches the regular expression server-temp-file-regexp. This is set up to distinguish certain "temporary" files.

If you set the variable server-window to a window or a frame, C-x # displays the server buffer in that window or in that frame.

While mail or another application is waiting for emacsclient to finish, emacsclient does not read terminal input. So the terminal that mail was using is effectively blocked for the duration. In order to edit with your principal Emacs, you need to be able to use it without using that terminal. There are three ways to do this:

If you run emacsclient with the option `--no-wait', it returns immediately without waiting for you to "finish" the buffer in Emacs. Note that server buffers created in this way are not killed automatically when you finish with them.

AC.17 Invoking emacsclient  

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AC.17 Invoking emacsclient

To run the emacsclient program, specify file names as arguments, and optionally line numbers as well. Do it like this:

emacsclient {[+line[column]] filename}...

This tells Emacs to visit each of the specified files; if you specify a line number for a certain file, Emacs moves to that line in the file. If you specify a column number as well, Emacs puts point on that column in the line.

Ordinarily, emacsclient does not return until you use the C-x # command on each of these buffers. When that happens, Emacs sends a message to the emacsclient program telling it to return.

But if you use the option `-n' or `--no-wait' when running emacsclient, then it returns immediately. (You can take as long as you like to edit the files in Emacs.)

The option `--alternate-editor=command' is useful when running emacsclient in a script. It specifies a command to run if emacsclient fails to contact Emacs. For example, the following setting for the EDITOR environment variable will always give an editor, even if Emacs is not running:

EDITOR="emacsclient --alternate-editor vi +%d %s"

The environment variable ALTERNATE_EDITOR has the same effect, but the value of the `--alternate-editor' takes precedence.

Alternatively, the file `etc/emacs.bash' defines a bash function which will communicate with a running Emacs server, or start one if none exists.

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AC.18 Hardcopy Output

The Emacs commands for making hardcopy let you print either an entire buffer or just part of one, either with or without page headers. See also the hardcopy commands of Dired (see section M.10 Miscellaneous File Operations) and the diary (see section AC.10.1 Commands Displaying Diary Entries).

M-x print-buffer
Print hardcopy of current buffer with page headings containing the file name and page number.
M-x lpr-buffer
Print hardcopy of current buffer without page headings.
M-x print-region
Like print-buffer but print only the current region.
M-x lpr-region
Like lpr-buffer but print only the current region.

The hardcopy commands (aside from the Postscript commands) pass extra switches to the lpr program based on the value of the variable lpr-switches. Its value should be a list of strings, each string an option starting with `-'. For example, to specify a line width of 80 columns for all the printing you do in Emacs, set lpr-switches like this:

(setq lpr-switches '("-w80"))

You can specify the printer to use by setting the variable printer-name.

The variable lpr-command specifies the name of the printer program to run; the default value depends on your operating system type. On most systems, the default is "lpr". The variable lpr-headers-switches similarly specifies the extra switches to use to make page headers. The variable lpr-add-switches controls whether to supply `-T' and `-J' options (suitable for lpr) to the printer program: nil means don't add them. lpr-add-switches should be nil if your printer program is not compatible with lpr.

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AC.19 PostScript Hardcopy

These commands convert buffer contents to PostScript, either printing it or leaving it in another Emacs buffer.

M-x ps-print-buffer
Print hardcopy of the current buffer in PostScript form.
M-x ps-print-region
Print hardcopy of the current region in PostScript form.
M-x ps-print-buffer-with-faces
Print hardcopy of the current buffer in PostScript form, showing the faces used in the text by means of PostScript features.
M-x ps-print-region-with-faces
Print hardcopy of the current region in PostScript form, showing the faces used in the text.
M-x ps-spool-buffer
Generate PostScript for the current buffer text.
M-x ps-spool-region
Generate PostScript for the current region.
M-x ps-spool-buffer-with-faces
Generate PostScript for the current buffer, showing the faces used.
M-x ps-spool-region-with-faces
Generate PostScript for the current region, showing the faces used.
M-x handwrite
Generates/prints PostScript for the current buffer as if handwritten.

The PostScript commands, ps-print-buffer and ps-print-region, print buffer contents in PostScript form. One command prints the entire buffer; the other, just the region. The corresponding `-with-faces' commands, ps-print-buffer-with-faces and ps-print-region-with-faces, use PostScript features to show the faces (fonts and colors) in the text properties of the text being printed.

If you are using a color display, you can print a buffer of program code with color highlighting by turning on Font-Lock mode in that buffer, and using ps-print-buffer-with-faces.

The commands whose names have `spool' instead of `print' generate the PostScript output in an Emacs buffer instead of sending it to the printer.

M-x handwrite is more frivolous. It generates a PostScript rendition of the current buffer as a cursive handwritten document. It can be customized in group handwrite. This function only supports ISO 8859-1 characters.

The following section describes variables for customizing these commands.

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AC.20 Variables for PostScript Hardcopy

All the PostScript hardcopy commands use the variables ps-lpr-command and ps-lpr-switches to specify how to print the output. ps-lpr-command specifies the command name to run, ps-lpr-switches specifies command line options to use, and ps-printer-name specifies the printer. If you don't set the first two variables yourself, they take their initial values from lpr-command and lpr-switches. If ps-printer-name is nil, printer-name is used.

The variable ps-print-header controls whether these commands add header lines to each page--set it to nil to turn headers off.

If your printer doesn't support colors, you should turn off color processing by setting ps-print-color-p to nil. By default, if the display supports colors, Emacs produces hardcopy output with color information; on black-and-white printers, colors are emulated with shades of gray. This might produce illegible output, even if your screen colors only use shades of gray.

By default, PostScript printing ignores the background colors of the faces, unless the variable ps-use-face-background is non-nil. This is to avoid unwanted interference with the zebra stripes and background image/text.

The variable ps-paper-type specifies which size of paper to format for; legitimate values include a4, a3, a4small, b4, b5, executive, ledger, legal, letter, letter-small, statement, tabloid. The default is letter. You can define additional paper sizes by changing the variable ps-page-dimensions-database.

The variable ps-landscape-mode specifies the orientation of printing on the page. The default is nil, which stands for "portrait" mode. Any non-nil value specifies "landscape" mode.

The variable ps-number-of-columns specifies the number of columns; it takes effect in both landscape and portrait mode. The default is 1.

The variable ps-font-family specifies which font family to use for printing ordinary text. Legitimate values include Courier, Helvetica, NewCenturySchlbk, Palatino and Times. The variable ps-font-size specifies the size of the font for ordinary text. It defaults to 8.5 points.

Emacs supports more scripts and characters than a typical PostScript printer. Thus, some of the characters in your buffer might not be printable using the fonts built into your printer. You can augment the fonts supplied with the printer with those from the GNU Intlfonts package, or you can instruct Emacs to use Intlfonts exclusively. The variable ps-multibyte-buffer controls this: the default value, nil, is appropriate for printing ASCII and Latin-1 characters; a value of non-latin-printer is for printers which have the fonts for ASCII, Latin-1, Japanese, and Korean characters built into them. A value of bdf-font arranges for the BDF fonts from the Intlfonts package to be used for all characters. Finally, a value of bdf-font-except-latin instructs the printer to use built-in fonts for ASCII and Latin-1 characters, and Intlfonts BDF fonts for the rest.

To be able to use the BDF fonts, Emacs needs to know where to find them. The variable bdf-directory-list holds the list of directories where Emacs should look for the fonts; the default value includes a single directory `/usr/local/share/emacs/fonts/bdf'.

Many other customization variables for these commands are defined and described in the Lisp files `ps-print.el' and `ps-mule.el'.

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AC.21 Sorting Text

Emacs provides several commands for sorting text in the buffer. All operate on the contents of the region (the text between point and the mark). They divide the text of the region into many sort records, identify a sort key for each record, and then reorder the records into the order determined by the sort keys. The records are ordered so that their keys are in alphabetical order, or, for numeric sorting, in numeric order. In alphabetic sorting, all upper-case letters `A' through `Z' come before lower-case `a', in accord with the ASCII character sequence.

The various sort commands differ in how they divide the text into sort records and in which part of each record is used as the sort key. Most of the commands make each line a separate sort record, but some commands use paragraphs or pages as sort records. Most of the sort commands use each entire sort record as its own sort key, but some use only a portion of the record as the sort key.

M-x sort-lines
Divide the region into lines, and sort by comparing the entire text of a line. A numeric argument means sort into descending order.

M-x sort-paragraphs
Divide the region into paragraphs, and sort by comparing the entire text of a paragraph (except for leading blank lines). A numeric argument means sort into descending order.

M-x sort-pages
Divide the region into pages, and sort by comparing the entire text of a page (except for leading blank lines). A numeric argument means sort into descending order.

M-x sort-fields
Divide the region into lines, and sort by comparing the contents of one field in each line. Fields are defined as separated by whitespace, so the first run of consecutive non-whitespace characters in a line constitutes field 1, the second such run constitutes field 2, etc.

Specify which field to sort by with a numeric argument: 1 to sort by field 1, etc. A negative argument means count fields from the right instead of from the left; thus, minus 1 means sort by the last field. If several lines have identical contents in the field being sorted, they keep the same relative order that they had in the original buffer.

M-x sort-numeric-fields
Like M-x sort-fields except the specified field is converted to an integer for each line, and the numbers are compared. `10' comes before `2' when considered as text, but after it when considered as a number. By default, numbers are interpreted according to sort-numeric-base, but numbers beginning with `0x' or `0' are interpreted as hexadecimal and octal, respectively.

M-x sort-columns
Like M-x sort-fields except that the text within each line used for comparison comes from a fixed range of columns. See below for an explanation.

M-x reverse-region
Reverse the order of the lines in the region. This is useful for sorting into descending order by fields or columns, since those sort commands do not have a feature for doing that.

For example, if the buffer contains this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
whether the file has changed on disk since it was last visited or
saved.  If it has, you are asked to confirm that you want to change
the buffer.

applying M-x sort-lines to the entire buffer produces this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
whether the file has changed on disk since it was last visited or

where the upper-case `O' sorts before all lower-case letters. If you use C-u 2 M-x sort-fields instead, you get this:

implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
On systems where clash detection (locking of files being edited) is
whether the file has changed on disk since it was last visited or

where the sort keys were `Emacs', `If', `buffer', `systems' and `the'.

M-x sort-columns requires more explanation. You specify the columns by putting point at one of the columns and the mark at the other column. Because this means you cannot put point or the mark at the beginning of the first line of the text you want to sort, this command uses an unusual definition of "region": all of the line point is in is considered part of the region, and so is all of the line the mark is in, as well as all the lines in between.

For example, to sort a table by information found in columns 10 to 15, you could put the mark on column 10 in the first line of the table, and point on column 15 in the last line of the table, and then run sort-columns. Equivalently, you could run it with the mark on column 15 in the first line and point on column 10 in the last line.

This can be thought of as sorting the rectangle specified by point and the mark, except that the text on each line to the left or right of the rectangle moves along with the text inside the rectangle. See section H.10 Rectangles.

Many of the sort commands ignore case differences when comparing, if sort-fold-case is non-nil.

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AC.22 Narrowing

Narrowing means focusing in on some portion of the buffer, making the rest temporarily inaccessible. The portion which you can still get to is called the accessible portion. Canceling the narrowing, which makes the entire buffer once again accessible, is called widening. The amount of narrowing in effect in a buffer at any time is called the buffer's restriction.

Narrowing can make it easier to concentrate on a single subroutine or paragraph by eliminating clutter. It can also be used to restrict the range of operation of a replace command or repeating keyboard macro.

C-x n n
Narrow down to between point and mark (narrow-to-region).
C-x n w
Widen to make the entire buffer accessible again (widen).
C-x n p
Narrow down to the current page (narrow-to-page).
C-x n d
Narrow down to the current defun (narrow-to-defun).

When you have narrowed down to a part of the buffer, that part appears to be all there is. You can't see the rest, you can't move into it (motion commands won't go outside the accessible part), you can't change it in any way. However, it is not gone, and if you save the file all the inaccessible text will be saved. The word `Narrow' appears in the mode line whenever narrowing is in effect.

The primary narrowing command is C-x n n (narrow-to-region). It sets the current buffer's restrictions so that the text in the current region remains accessible, but all text before the region or after the region is inaccessible. Point and mark do not change.

Alternatively, use C-x n p (narrow-to-page) to narrow down to the current page. See section T.4 Pages, for the definition of a page. C-x n d (narrow-to-defun) narrows down to the defun containing point (see section U.2 Top-Level Definitions, or Defuns).

The way to cancel narrowing is to widen with C-x n w (widen). This makes all text in the buffer accessible again.

You can get information on what part of the buffer you are narrowed down to using the C-x = command. See section D.9 Cursor Position Information.

Because narrowing can easily confuse users who do not understand it, narrow-to-region is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; if you enable the command, confirmation will no longer be required for it. See section AD.4.11 Disabling Commands.

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AC.23 Two-Column Editing

Two-column mode lets you conveniently edit two side-by-side columns of text. It uses two side-by-side windows, each showing its own buffer.

There are three ways to enter two-column mode:

F2 2 or C-x 6 2
Enter two-column mode with the current buffer on the left, and on the right, a buffer whose name is based on the current buffer's name (2C-two-columns). If the right-hand buffer doesn't already exist, it starts out empty; the current buffer's contents are not changed.

This command is appropriate when the current buffer is empty or contains just one column and you want to add another column.

F2 s or C-x 6 s
Split the current buffer, which contains two-column text, into two buffers, and display them side by side (2C-split). The current buffer becomes the left-hand buffer, but the text in the right-hand column is moved into the right-hand buffer. The current column specifies the split point. Splitting starts with the current line and continues to the end of the buffer.

This command is appropriate when you have a buffer that already contains two-column text, and you wish to separate the columns temporarily.

F2 b buffer RET
C-x 6 b buffer RET
Enter two-column mode using the current buffer as the left-hand buffer, and using buffer buffer as the right-hand buffer (2C-associate-buffer).

F2 s or C-x 6 s looks for a column separator, which is a string that appears on each line between the two columns. You can specify the width of the separator with a numeric argument to F2 s; that many characters, before point, constitute the separator string. By default, the width is 1, so the column separator is the character before point.

When a line has the separator at the proper place, F2 s puts the text after the separator into the right-hand buffer, and deletes the separator. Lines that don't have the column separator at the proper place remain unsplit; they stay in the left-hand buffer, and the right-hand buffer gets an empty line to correspond. (This is the way to write a line that "spans both columns while in two-column mode": write it in the left-hand buffer, and put an empty line in the right-hand buffer.)

The command C-x 6 RET or F2 RET (2C-newline) inserts a newline in each of the two buffers at corresponding positions. This is the easiest way to add a new line to the two-column text while editing it in split buffers.

When you have edited both buffers as you wish, merge them with F2 1 or C-x 6 1 (2C-merge). This copies the text from the right-hand buffer as a second column in the other buffer. To go back to two-column editing, use F2 s.

Use F2 d or C-x 6 d to dissociate the two buffers, leaving each as it stands (2C-dissociate). If the other buffer, the one not current when you type F2 d, is empty, F2 d kills it.

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AC.24 Editing Binary Files

There is a special major mode for editing binary files: Hexl mode. To use it, use M-x hexl-find-file instead of C-x C-f to visit the file. This command converts the file's contents to hexadecimal and lets you edit the translation. When you save the file, it is converted automatically back to binary.

You can also use M-x hexl-mode to translate an existing buffer into hex. This is useful if you visit a file normally and then discover it is a binary file.

Ordinary text characters overwrite in Hexl mode. This is to reduce the risk of accidentally spoiling the alignment of data in the file. There are special commands for insertion. Here is a list of the commands of Hexl mode:

Insert a byte with a code typed in decimal.

Insert a byte with a code typed in octal.

Insert a byte with a code typed in hex.

C-x [
Move to the beginning of a 1k-byte "page."

C-x ]
Move to the end of a 1k-byte "page."

Move to an address specified in hex.

Move to an address specified in decimal.

C-c C-c
Leave Hexl mode, going back to the major mode this buffer had before you invoked hexl-mode.

Other Hexl commands let you insert strings (sequences) of binary bytes, move by shorts or ints, etc.; type C-h a hexl-RET for details.

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AC.25 Saving Emacs Sessions

You can use the Desktop library to save the state of Emacs from one session to another. Saving the state means that Emacs starts up with the same set of buffers, major modes, buffer positions, and so on that the previous Emacs session had.

To use Desktop, you should use the Customization buffer (see section AD.2.2 Easy Customization Interface) to set desktop-enable to a non-nil value, or add these lines at the end of your `.emacs' file:


The first time you save the state of the Emacs session, you must do it manually, with the command M-x desktop-save. Once you have done that, exiting Emacs will save the state again--not only the present Emacs session, but also subsequent sessions. You can also save the state at any time, without exiting Emacs, by typing M-x desktop-save again.

In order for Emacs to recover the state from a previous session, you must start it with the same current directory as you used when you started the previous session. This is because desktop-read looks in the current directory for the file to read. This means that you can have separate saved sessions in different directories; the directory in which you start Emacs will control which saved session to use.

The variable desktop-files-not-to-save controls which files are excluded from state saving. Its value is a regular expression that matches the files to exclude. By default, remote (ftp-accessed) files are excluded; this is because visiting them again in the subsequent session would be slow. If you want to include these files in state saving, set desktop-files-not-to-save to "^$". See section M.13 Remote Files.

The Saveplace library provides a simpler feature that records your position in each file when you kill its buffer (or kill Emacs), and jumps to the same position when you visit the file again (even in another Emacs session). Use M-x toggle-save-place to turn on place-saving in a given file. Customize the option save-place to turn it on for all files in each session.

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AC.26 Recursive Editing Levels

A recursive edit is a situation in which you are using Emacs commands to perform arbitrary editing while in the middle of another Emacs command. For example, when you type C-r inside of a query-replace, you enter a recursive edit in which you can change the current buffer. On exiting from the recursive edit, you go back to the query-replace.

Exiting the recursive edit means returning to the unfinished command, which continues execution. The command to exit is C-M-c (exit-recursive-edit).

You can also abort the recursive edit. This is like exiting, but also quits the unfinished command immediately. Use the command C-] (abort-recursive-edit) to do this. See section AD.8 Quitting and Aborting.

The mode line shows you when you are in a recursive edit by displaying square brackets around the parentheses that always surround the major and minor mode names. Every window's mode line shows this in the same way, since being in a recursive edit is true of Emacs as a whole rather than any particular window or buffer.

It is possible to be in recursive edits within recursive edits. For example, after typing C-r in a query-replace, you may type a command that enters the debugger. This begins a recursive editing level for the debugger, within the recursive editing level for C-r. Mode lines display a pair of square brackets for each recursive editing level currently in progress.

Exiting the inner recursive edit (such as, with the debugger c command) resumes the command running in the next level up. When that command finishes, you can then use C-M-c to exit another recursive editing level, and so on. Exiting applies to the innermost level only. Aborting also gets out of only one level of recursive edit; it returns immediately to the command level of the previous recursive edit. If you wish, you can then abort the next recursive editing level.

Alternatively, the command M-x top-level aborts all levels of recursive edits, returning immediately to the top-level command reader.

The text being edited inside the recursive edit need not be the same text that you were editing at top level. It depends on what the recursive edit is for. If the command that invokes the recursive edit selects a different buffer first, that is the buffer you will edit recursively. In any case, you can switch buffers within the recursive edit in the normal manner (as long as the buffer-switching keys have not been rebound). You could probably do all the rest of your editing inside the recursive edit, visiting files and all. But this could have surprising effects (such as stack overflow) from time to time. So remember to exit or abort the recursive edit when you no longer need it.

In general, we try to minimize the use of recursive editing levels in GNU Emacs. This is because they constrain you to "go back" in a particular order--from the innermost level toward the top level. When possible, we present different activities in separate buffers so that you can switch between them as you please. Some commands switch to a new major mode which provides a command to switch back. These approaches give you more flexibility to go back to unfinished tasks in the order you choose.

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AC.27 Emulation

GNU Emacs can be programmed to emulate (more or less) most other editors. Standard facilities can emulate these:

CRiSP/Brief (PC editor)
You can turn on key bindings to emulate the CRiSP/Brief editor with M-x crisp-mode. Note that this rebinds M-x to exit Emacs unless you change the user option crisp-override-meta-x. You can also use the command M-x scroll-all-mode or set the user option crisp-load-scroll-all to emulate CRiSP's scroll-all feature (scrolling all windows together).

EDT (DEC VMS editor)
Turn on EDT emulation with M-x edt-emulation-on. M-x edt-emulation-off restores normal Emacs command bindings.

Most of the EDT emulation commands are keypad keys, and most standard Emacs key bindings are still available. The EDT emulation rebindings are done in the global keymap, so there is no problem switching buffers or major modes while in EDT emulation.

"PC" bindings
The command M-x pc-bindings-mode sets up certain key bindings for "PC compatibility"---what people are often used to on PCs--as follows: Delete and its variants delete forward instead of backward, C-Backspace kills backward a word (as C-Delete normally would), M-Backspace does undo, Home and End move to beginning and end of line, C-Home and C-End move to beginning and end of buffer and C-Escape does list-buffers.

PC Selection mode
The command M-x pc-selection-mode enables a global minor mode that emulates the mark, copy, cut and paste commands of various other systems--an interface known as CUA. It establishes the key bindings of PC mode, and also modifies the bindings of the cursor keys and the next, prior, home and end keys. It does not provide the full set of CUA key bindings--the fundamental Emacs keys C-c, C-v and C-x are not changed.

The standard keys for moving around (right, left, up, down, home, end, prior, next, called "move-keys") deactivate the mark in PC selection mode. However, using Shift together with the "move keys" activates the region over which they move. The copy, cut and paste functions are available on C-insert, S-delete and S-insert respectively.

The s-region package provides similar, but less complete, facilities.

TPU (DEC VMS editor)
M-x tpu-edt-on turns on emulation of the TPU editor emulating EDT.

vi (Berkeley editor)
Viper is the newest emulator for vi. It implements several levels of emulation; level 1 is closest to vi itself, while level 5 departs somewhat from strict emulation to take advantage of the capabilities of Emacs. To invoke Viper, type M-x viper-mode; it will guide you the rest of the way and ask for the emulation level. See Info file `viper', node `Top'.

vi (another emulator)
M-x vi-mode enters a major mode that replaces the previously established major mode. All of the vi commands that, in real vi, enter "input" mode are programmed instead to return to the previous major mode. Thus, ordinary Emacs serves as vi's "input" mode.

Because vi emulation works through major modes, it does not work to switch buffers during emulation. Return to normal Emacs first.

If you plan to use vi emulation much, you probably want to bind a key to the vi-mode command.

vi (alternate emulator)
M-x vip-mode invokes another vi emulator, said to resemble real vi more thoroughly than M-x vi-mode. "Input" mode in this emulator is changed from ordinary Emacs so you can use ESC to go back to emulated vi command mode. To get from emulated vi command mode back to ordinary Emacs, type C-z.

This emulation does not work through major modes, and it is possible to switch buffers in various ways within the emulator. It is not so necessary to assign a key to the command vip-mode as it is with vi-mode because terminating insert mode does not use it.

See Info file `vip', node `Top', for full information.

WordStar (old wordprocessor)
M-x wordstar-mode provides a major mode with WordStar-like key bindings.

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AC.28 Hyperlinking and Navigation Features

Various modes documented elsewhere have hypertext features so that you can follow links, usually by clicking Mouse-2 on the link or typing RET while point is on the link. Info mode, Help mode and the Dired-like modes are examples. The Tags facility links between uses and definitions in source files, see W.2 Tags Tables. Imenu provides navigation amongst items indexed in the current buffer, see U.2.3 Imenu. Info-lookup provides mode-specific lookup of definitions in Info indexes, see U.6 Documentation Lookup. Speedbar maintains a frame in which links to files, and locations in files are displayed, see P.9 Making and Using a Speedbar Frame.

Other non-mode-specific facilities described in this section enable following links from the current buffer in a context-sensitive fashion.

AC.28.1 Following URLs  Following URLs.
AC.28.2 Activating URLs  Activating URLs.
AC.28.3 Finding Files and URLs at Point  Finding files etc. at point.
AC.28.4 Finding Function and Variable Definitions  Finding function and variable definitions.

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AC.28.1 Following URLs

M-x browse-url RET url RET
Load a URL into a Web browser.

The Browse-URL package provides facilities for following URLs specifying links on the World Wide Web. Usually this works by invoking a web browser, but you can, for instance, arrange to invoke compose-mail from `mailto:' URLs.

The general way to use this feature is to type M-x browse-url, which displays a specified URL. If point is located near a plausible URL, that URL is used as the default. Other commands are available which you might like to bind to keys, such as browse-url-at-point and browse-url-at-mouse.

You can customize Browse-URL's behavior via various options in the browse-url Customize group, particularly browse-url-browser-function. You can invoke actions dependent on the type of URL by defining browse-url-browser-function as an association list. The package's commentary available via C-h p provides more information. Packages with facilities for following URLs should always go through Browse-URL, so that the customization options for Browse-URL will affect all browsing in Emacs.

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AC.28.2 Activating URLs

M-x goto-address
Activate URLs and e-mail addresses in the current buffer.

You can make URLs in the current buffer active with M-x goto-address. This finds all the URLs in the buffer, and establishes bindings for Mouse-2 and C-c RET on them. After activation, if you click on a URL with Mouse-2, or move to a URL and type C-c RET, that will display the web page that the URL specifies. For a `mailto' URL, it sends mail instead, using your selected mail-composition method (see section Z.6 Mail-Composition Methods).

It can be useful to add goto-address to mode hooks and the hooks used to display an incoming message. rmail-show-message-hook is the appropriate hook for Rmail, and mh-show-mode-hook for MH-E. This is not needed for Gnus, which has a similar feature of its own.

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AC.28.3 Finding Files and URLs at Point

FFAP mode replaces certain key bindings for finding files, including C-x C-f, with commands that provide more sensitive defaults. These commands behave like the ordinary ones when given a prefix argument. Otherwise, they get the default file name or URL from the text around point. If what is found in the buffer has the form of a URL rather than a file name, the commands use browse-url to view it.

This feature is useful for following references in mail or news buffers, `README' files, `MANIFEST' files, and so on. The `ffap' package's commentary available via C-h p and the ffap Custom group provide details.

You can turn on FFAP minor mode to make the following key bindings and to install hooks for using ffap in Rmail, Gnus and VM article buffers.

C-x C-f filename RET
Find filename, guessing a default from text around point (find-file-at-point).
C-x 4 f
ffap-other-window, analogous to find-file-other-window.
C-x 5 f
ffap-other-frame, analogous to find-file-other-frame.
M-x ffap-next
Search buffer for next file name or URL, then find that file or URL.
C-x d directory RET
Start Dired on directory, defaulting to the directory name at point (ffap-dired-at-point).
ffap-at-mouse finds the file guessed from text around the position of a mouse click.
Display a menu of files and URLs mentioned in current buffer, then find the one you select (ffap-menu).

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AC.28.4 Finding Function and Variable Definitions

M-x find-function RET function RET
Find the definition of function in its source file.
M-x find-variable RET variable RET
Find the definition of variable in its source file.
M-x find-function-on-key RET key
Find the definition of the function that key invokes.

These commands provide an easy way to find the definitions of Emacs Lisp functions and variables. They are similar in purpose to the Tags facility (see section W.2 Tags Tables), but don't require a tags table; on the other hand, they only work for function and variable definitions that are already loaded in the Emacs session.

To find the definition of a function, use M-x find-function. M-x find-variable finds the definition of a specified variable. M-x find-function-on-key finds the definition of the function bound to a specified key.

To use these commands, you must have the Lisp source (`.el') files available along with the compiled (`.elc') files, in directories in load-path. You can use compressed source files if you enable Auto Compression mode. These commands only handle definitions written in Lisp, not primitive functions or variables defined in the C code of Emacs.

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AC.29 Dissociated Press

M-x dissociated-press is a command for scrambling a file of text either word by word or character by character. Starting from a buffer of straight English, it produces extremely amusing output. The input comes from the current Emacs buffer. Dissociated Press writes its output in a buffer named `*Dissociation*', and redisplays that buffer after every couple of lines (approximately) so you can read the output as it comes out.

Dissociated Press asks every so often whether to continue generating output. Answer n to stop it. You can also stop at any time by typing C-g. The dissociation output remains in the `*Dissociation*' buffer for you to copy elsewhere if you wish.

Dissociated Press operates by jumping at random from one point in the buffer to another. In order to produce plausible output rather than gibberish, it insists on a certain amount of overlap between the end of one run of consecutive words or characters and the start of the next. That is, if it has just output `president' and then decides to jump to a different point in the file, it might spot the `ent' in `pentagon' and continue from there, producing `presidentagon'.(15) Long sample texts produce the best results.

A positive argument to M-x dissociated-press tells it to operate character by character, and specifies the number of overlap characters. A negative argument tells it to operate word by word and specifies the number of overlap words. In this mode, whole words are treated as the elements to be permuted, rather than characters. No argument is equivalent to an argument of two. For your againformation, the output goes only into the buffer `*Dissociation*'. The buffer you start with is not changed.

Dissociated Press produces nearly the same results as a Markov chain based on a frequency table constructed from the sample text. It is, however, an independent, ignoriginal invention. Dissociated Press techniquitously copies several consecutive characters from the sample between random choices, whereas a Markov chain would choose randomly for each word or character. This makes for more plausible sounding results, and runs faster.

It is a mustatement that too much use of Dissociated Press can be a developediment to your real work. Sometimes to the point of outragedy. And keep dissociwords out of your documentation, if you want it to be well userenced and properbose. Have fun. Your buggestions are welcome.

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AC.30 Other Amusements

If you are a little bit bored, you can try M-x hanoi. If you are considerably bored, give it a numeric argument. If you are very, very bored, try an argument of 9. Sit back and watch.

If you want a little more personal involvement, try M-x gomoku, which plays the game Go Moku with you.

M-x blackbox, M-x mpuz and M-x 5x5 are kinds of puzzles. blackbox challenges you to determine the location of objects inside a box by tomography. mpuz displays a multiplication puzzle with letters standing for digits in a code that you must guess--to guess a value, type a letter and then the digit you think it stands for. The aim of 5x5 is to fill in all the squares.

M-x decipher helps you to cryptanalyze a buffer which is encrypted in a simple monoalphabetic substitution cipher.

M-x dunnet runs an adventure-style exploration game, which is a bigger sort of puzzle.

M-x lm runs a relatively non-participatory game in which a robot attempts to maneuver towards a tree at the center of the window based on unique olfactory cues from each of the four directions.

M-x life runs Conway's "Life" cellular automaton.

M-x morse-region converts text in a region to Morse code and M-x unmorse-region converts it back. No cause for remorse.

M-x pong plays a Pong-like game, bouncing the ball off opposing bats.

M-x solitaire plays a game of solitaire in which you jump pegs across other pegs.

M-x studlify-region studlify-cases the region, producing text like this:

M-x stUdlIfY-RegioN stUdlIfY-CaSeS thE region.

M-x tetris runs an implementation of the well-known Tetris game. Likewise, M-x snake provides an implementation of Snake.

When you are frustrated, try the famous Eliza program. Just do M-x doctor. End each input by typing RET twice.

When you are feeling strange, type M-x yow.

The command M-x zone plays games with the display when Emacs is idle.

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