This is ../info/emacs, produced by makeinfo version 4.0f from
emacs.texi.
This is the Fourteenth edition of the `GNU Emacs Manual', updated
for Emacs version 21.2.
INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Emacs: (emacs). The extensible self-documenting text editor.
END-INFO-DIR-ENTRY
Published by the Free Software Foundation 59 Temple Place, Suite 330
Boston, MA 02111-1307 USA
Copyright (C)
1985,1986,1987,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002
Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "The GNU Manifesto", "Distribution" and "GNU
GENERAL PUBLIC LICENSE", with the Front-Cover texts being "A GNU
Manual," and with the Back-Cover Texts as in (a) below. A copy of the
license is included in the section entitled "GNU Free Documentation
License."
(a) The FSF's Back-Cover Text is: "You have freedom to copy and
modify this GNU Manual, like GNU software. Copies published by the Free
Software Foundation raise funds for GNU development."
File: emacs, Node: After a Crash, Next: Emergency Escape, Prev: Memory Full, Up: Lossage
Recovery After a Crash
----------------------
If Emacs or the computer crashes, you can recover the files you were
editing at the time of the crash from their auto-save files. To do
this, start Emacs again and type the command `M-x recover-session'.
This command initially displays a buffer which lists interrupted
session files, each with its date. You must choose which session to
recover from. Typically the one you want is the most recent one. Move
point to the one you choose, and type `C-c C-c'.
Then `recover-session' asks about each of the files that you were
editing during that session; it asks whether to recover that file. If
you answer `y' for a file, it shows the dates of that file and its
auto-save file, then asks once again whether to recover that file. For
the second question, you must confirm with `yes'. If you do, Emacs
visits the file but gets the text from the auto-save file.
When `recover-session' is done, the files you've chosen to recover
are present in Emacs buffers. You should then save them. Only
this--saving them--updates the files themselves.
File: emacs, Node: Emergency Escape, Next: Total Frustration, Prev: After a Crash, Up: Lossage
Emergency Escape
----------------
Because at times there have been bugs causing Emacs to loop without
checking `quit-flag', a special feature causes Emacs to be suspended
immediately if you type a second `C-g' while the flag is already set,
so you can always get out of GNU Emacs. Normally Emacs recognizes and
clears `quit-flag' (and quits!) quickly enough to prevent this from
happening. (On MS-DOS and compatible systems, type `C-<BREAK>' twice.)
When you resume Emacs after a suspension caused by multiple `C-g', it
asks two questions before going back to what it had been doing:
Auto-save? (y or n)
Abort (and dump core)? (y or n)
Answer each one with `y' or `n' followed by <RET>.
Saying `y' to `Auto-save?' causes immediate auto-saving of all
modified buffers in which auto-saving is enabled.
Saying `y' to `Abort (and dump core)?' causes an illegal instruction
to be executed, dumping core. This is to enable a wizard to figure out
why Emacs was failing to quit in the first place. Execution does not
continue after a core dump. If you answer `n', execution does
continue. With luck, GNU Emacs will ultimately check `quit-flag' and
quit normally. If not, and you type another `C-g', it is suspended
again.
If Emacs is not really hung, just slow, you may invoke the double
`C-g' feature without really meaning to. Then just resume and answer
`n' to both questions, and you will arrive at your former state.
Presumably the quit you requested will happen soon.
The double `C-g' feature is turned off when Emacs is running under
the X Window System, since you can use the window manager to kill Emacs
or to create another window and run another program.
On MS-DOS and compatible systems, the emergency escape feature is
sometimes unavailable, even if you press `C-<BREAK>' twice, when some
system call (MS-DOS or BIOS) hangs, or when Emacs is stuck in a very
tight endless loop (in C code, *not* in Lisp code).
File: emacs, Node: Total Frustration, Prev: Emergency Escape, Up: Lossage
Help for Total Frustration
--------------------------
If using Emacs (or something else) becomes terribly frustrating and
none of the techniques described above solve the problem, Emacs can
still help you.
First, if the Emacs you are using is not responding to commands, type
`C-g C-g' to get out of it and then start a new one.
Second, type `M-x doctor <RET>'.
The doctor will help you feel better. Each time you say something to
the doctor, you must end it by typing <RET> <RET>. This lets the
doctor know you are finished.
File: emacs, Node: Bugs, Next: Contributing, Prev: Lossage, Up: Top
Reporting Bugs
==============
Sometimes you will encounter a bug in Emacs. Although we cannot
promise we can or will fix the bug, and we might not even agree that it
is a bug, we want to hear about problems you encounter. Often we agree
they are bugs and want to fix them.
To make it possible for us to fix a bug, you must report it. In
order to do so effectively, you must know when and how to do it.
Before reporting a bug, it is a good idea to see if it is already
known. You can find the list of known problems in the file
`etc/PROBLEMS' in the Emacs distribution; type `C-h P' to read it.
Some additional user-level problems can be found in *Note Bugs and
problems: (efaq)Bugs and problems. Looking up your problem in these
two documents might provide you with a solution or a work-around, or
give you additional information about related issues.
* Menu:
* Criteria: Bug Criteria. Have you really found a bug?
* Understanding Bug Reporting:: How to report a bug effectively.
* Checklist:: Steps to follow for a good bug report.
* Sending Patches:: How to send a patch for GNU Emacs.
File: emacs, Node: Bug Criteria, Next: Understanding Bug Reporting, Up: Bugs
When Is There a Bug
-------------------
If Emacs executes an illegal instruction, or dies with an operating
system error message that indicates a problem in the program (as
opposed to something like "disk full"), then it is certainly a bug.
If Emacs updates the display in a way that does not correspond to
what is in the buffer, then it is certainly a bug. If a command seems
to do the wrong thing but the problem corrects itself if you type
`C-l', it is a case of incorrect display updating.
Taking forever to complete a command can be a bug, but you must make
certain that it was really Emacs's fault. Some commands simply take a
long time. Type `C-g' (`C-<BREAK>' on MS-DOS) and then `C-h l' to see
whether the input Emacs received was what you intended to type; if the
input was such that you _know_ it should have been processed quickly,
report a bug. If you don't know whether the command should take a long
time, find out by looking in the manual or by asking for assistance.
If a command you are familiar with causes an Emacs error message in a
case where its usual definition ought to be reasonable, it is probably a
bug.
If a command does the wrong thing, that is a bug. But be sure you
know for certain what it ought to have done. If you aren't familiar
with the command, or don't know for certain how the command is supposed
to work, then it might actually be working right. Rather than jumping
to conclusions, show the problem to someone who knows for certain.
Finally, a command's intended definition may not be the best
possible definition for editing with. This is a very important sort of
problem, but it is also a matter of judgment. Also, it is easy to come
to such a conclusion out of ignorance of some of the existing features.
It is probably best not to complain about such a problem until you
have checked the documentation in the usual ways, feel confident that
you understand it, and know for certain that what you want is not
available. If you are not sure what the command is supposed to do
after a careful reading of the manual, check the index and glossary for
any terms that may be unclear.
If after careful rereading of the manual you still do not understand
what the command should do, that indicates a bug in the manual, which
you should report. The manual's job is to make everything clear to
people who are not Emacs experts--including you. It is just as
important to report documentation bugs as program bugs.
If the on-line documentation string of a function or variable
disagrees with the manual, one of them must be wrong; that is a bug.
File: emacs, Node: Understanding Bug Reporting, Next: Checklist, Prev: Bug Criteria, Up: Bugs
Understanding Bug Reporting
---------------------------
When you decide that there is a bug, it is important to report it
and to report it in a way which is useful. What is most useful is an
exact description of what commands you type, starting with the shell
command to run Emacs, until the problem happens.
The most important principle in reporting a bug is to report
_facts_. Hypotheses and verbal descriptions are no substitute for the
detailed raw data. Reporting the facts is straightforward, but many
people strain to posit explanations and report them instead of the
facts. If the explanations are based on guesses about how Emacs is
implemented, they will be useless; meanwhile, lacking the facts, we will
have no real information about the bug.
For example, suppose that you type `C-x C-f /glorp/baz.ugh <RET>',
visiting a file which (you know) happens to be rather large, and Emacs
displayed `I feel pretty today'. The best way to report the bug is
with a sentence like the preceding one, because it gives all the facts.
A bad way would be to assume that the problem is due to the size of
the file and say, "I visited a large file, and Emacs displayed `I feel
pretty today'." This is what we mean by "guessing explanations." The
problem is just as likely to be due to the fact that there is a `z' in
the file name. If this is so, then when we got your report, we would
try out the problem with some "large file," probably with no `z' in its
name, and not see any problem. There is no way in the world that we
could guess that we should try visiting a file with a `z' in its name.
Alternatively, the problem might be due to the fact that the file
starts with exactly 25 spaces. For this reason, you should make sure
that you inform us of the exact contents of any file that is needed to
reproduce the bug. What if the problem only occurs when you have typed
the `C-x C-a' command previously? This is why we ask you to give the
exact sequence of characters you typed since starting the Emacs session.
You should not even say "visit a file" instead of `C-x C-f' unless
you _know_ that it makes no difference which visiting command is used.
Similarly, rather than saying "if I have three characters on the line,"
say "after I type `<RET> A B C <RET> C-p'," if that is the way you
entered the text.
So please don't guess any explanations when you report a bug. If you
want to actually _debug_ the problem, and report explanations that are
more than guesses, that is useful--but please include the facts as well.
File: emacs, Node: Checklist, Next: Sending Patches, Prev: Understanding Bug Reporting, Up: Bugs
Checklist for Bug Reports
-------------------------
The best way to send a bug report is to mail it electronically to the
Emacs maintainers at <bug-gnu-emacs@gnu.org>, or to
<emacs-pretest-bug@gnu.org> if you are pretesting an Emacs beta
release. (If you want to suggest a change as an improvement, use the
same address.)
If you'd like to read the bug reports, you can find them on the
newsgroup `gnu.emacs.bug'; keep in mind, however, that as a spectator
you should not criticize anything about what you see there. The
purpose of bug reports is to give information to the Emacs maintainers.
Spectators are welcome only as long as they do not interfere with
this. In particular, some bug reports contain fairly large amounts of
data; spectators should not complain about this.
Please do not post bug reports using netnews; mail is more reliable
than netnews about reporting your correct address, which we may need in
order to ask you for more information. If your data is more than
500,000 bytes, please don't include it directly in the bug report;
instead, offer to send it on request, or make it available by ftp and
say where.
If you can't send electronic mail, then mail the bug report on paper
or machine-readable media to this address:
GNU Emacs Bugs
Free Software Foundation
59 Temple Place, Suite 330
Boston, MA 02111-1307 USA
We do not promise to fix the bug; but if the bug is serious, or
ugly, or easy to fix, chances are we will want to.
A convenient way to send a bug report for Emacs is to use the command
`M-x report-emacs-bug'. This sets up a mail buffer (*note Sending
Mail::) and automatically inserts _some_ of the essential information.
However, it cannot supply all the necessary information; you should
still read and follow the guidelines below, so you can enter the other
crucial information by hand before you send the message.
To enable maintainers to investigate a bug, your report should
include all these things:
* The version number of Emacs. Without this, we won't know whether
there is any point in looking for the bug in the current version
of GNU Emacs.
You can get the version number by typing `M-x emacs-version
<RET>'. If that command does not work, you probably have something
other than GNU Emacs, so you will have to report the bug somewhere
else.
* The type of machine you are using, and the operating system name
and version number. `M-x emacs-version <RET>' provides this
information too. Copy its output from the `*Messages*' buffer, so
that you get it all and get it accurately.
* The operands given to the `configure' command when Emacs was
installed.
* A complete list of any modifications you have made to the Emacs
source. (We may not have time to investigate the bug unless it
happens in an unmodified Emacs. But if you've made modifications
and you don't tell us, you are sending us on a wild goose chase.)
Be precise about these changes. A description in English is not
enough--send a context diff for them.
Adding files of your own, or porting to another machine, is a
modification of the source.
* Details of any other deviations from the standard procedure for
installing GNU Emacs.
* The complete text of any files needed to reproduce the bug.
If you can tell us a way to cause the problem without visiting any
files, please do so. This makes it much easier to debug. If you
do need files, make sure you arrange for us to see their exact
contents. For example, it can often matter whether there are
spaces at the ends of lines, or a newline after the last line in
the buffer (nothing ought to care whether the last line is
terminated, but try telling the bugs that).
* The precise commands we need to type to reproduce the bug.
The easy way to record the input to Emacs precisely is to write a
dribble file. To start the file, execute the Lisp expression
(open-dribble-file "~/dribble")
using `M-:' or from the `*scratch*' buffer just after starting
Emacs. From then on, Emacs copies all your input to the specified
dribble file until the Emacs process is killed.
* For possible display bugs, the terminal type (the value of
environment variable `TERM'), the complete termcap entry for the
terminal from `/etc/termcap' (since that file is not identical on
all machines), and the output that Emacs actually sent to the
terminal.
The way to collect the terminal output is to execute the Lisp
expression
(open-termscript "~/termscript")
using `M-:' or from the `*scratch*' buffer just after starting
Emacs. From then on, Emacs copies all terminal output to the
specified termscript file as well, until the Emacs process is
killed. If the problem happens when Emacs starts up, put this
expression into your `.emacs' file so that the termscript file
will be open when Emacs displays the screen for the first time.
Be warned: it is often difficult, and sometimes impossible, to fix
a terminal-dependent bug without access to a terminal of the type
that stimulates the bug.
* If non-ASCII text or internationalization is relevant, the locale
that was current when you started Emacs. On GNU/Linux and Unix
systems, or if you use a Posix-style shell such as Bash, you can
use this shell command to view the relevant values:
echo LC_ALL=$LC_ALL LC_COLLATE=$LC_COLLATE LC_TYPE=$LC_TYPE \
LC_MESSAGES=$LC_MESSAGES LC_TIME=$LC_TIME LANG=$LANG
Alternatively, use the `locale' command, if your system has it, to
display your locale settings.
You can use the `M-!' command to execute these commands from
Emacs, and then copy the output from the `*Messages*' buffer into
the bug report. Alternatively, `M-x getenv <RET> LC_ALL <RET>'
will display the value of `LC_ALL' in the echo area, and you can
copy its output from the `*Messages*' buffer.
* A description of what behavior you observe that you believe is
incorrect. For example, "The Emacs process gets a fatal signal,"
or, "The resulting text is as follows, which I think is wrong."
Of course, if the bug is that Emacs gets a fatal signal, then one
can't miss it. But if the bug is incorrect text, the maintainer
might fail to notice what is wrong. Why leave it to chance?
Even if the problem you experience is a fatal signal, you should
still say so explicitly. Suppose something strange is going on,
such as, your copy of the source is out of sync, or you have
encountered a bug in the C library on your system. (This has
happened!) Your copy might crash and the copy here might not. If
you _said_ to expect a crash, then when Emacs here fails to crash,
we would know that the bug was not happening. If you don't say to
expect a crash, then we would not know whether the bug was
happening--we would not be able to draw any conclusion from our
observations.
* If the bug is that the Emacs Manual or the Emacs Lisp Reference
Manual fails to describe the actual behavior of Emacs, or that the
text is confusing, copy in the text from the online manual which
you think is at fault. If the section is small, just the section
name is enough.
* If the manifestation of the bug is an Emacs error message, it is
important to report the precise text of the error message, and a
backtrace showing how the Lisp program in Emacs arrived at the
error.
To get the error message text accurately, copy it from the
`*Messages*' buffer into the bug report. Copy all of it, not just
part.
To make a backtrace for the error, use `M-x toggle-debug-on-error'
before the error happens (that is to say, you must give that
command and then make the bug happen). This causes the error to
run the Lisp debugger, which shows you a backtrace. Copy the text
of the debugger's backtrace into the bug report. *Note The Lisp
Debugger: (elisp)Debugger, for information on debugging Emacs Lisp
programs with the Edebug package.
This use of the debugger is possible only if you know how to make
the bug happen again. If you can't make it happen again, at least
copy the whole error message.
* Check whether any programs you have loaded into the Lisp world,
including your `.emacs' file, set any variables that may affect the
functioning of Emacs. Also, see whether the problem happens in a
freshly started Emacs without loading your `.emacs' file (start
Emacs with the `-q' switch to prevent loading the init file). If
the problem does _not_ occur then, you must report the precise
contents of any programs that you must load into the Lisp world in
order to cause the problem to occur.
* If the problem does depend on an init file or other Lisp programs
that are not part of the standard Emacs system, then you should
make sure it is not a bug in those programs by complaining to
their maintainers first. After they verify that they are using
Emacs in a way that is supposed to work, they should report the
bug.
* If you wish to mention something in the GNU Emacs source, show the
line of code with a few lines of context. Don't just give a line
number.
The line numbers in the development sources don't match those in
your sources. It would take extra work for the maintainers to
determine what code is in your version at a given line number, and
we could not be certain.
* Additional information from a C debugger such as GDB might enable
someone to find a problem on a machine which he does not have
available. If you don't know how to use GDB, please read the GDB
manual--it is not very long, and using GDB is easy. You can find
the GDB distribution, including the GDB manual in online form, in
most of the same places you can find the Emacs distribution. To
run Emacs under GDB, you should switch to the `src' subdirectory
in which Emacs was compiled, then do `gdb emacs'. It is important
for the directory `src' to be current so that GDB will read the
`.gdbinit' file in this directory.
However, you need to think when you collect the additional
information if you want it to show what causes the bug.
For example, many people send just a backtrace, but that is not
very useful by itself. A simple backtrace with arguments often
conveys little about what is happening inside GNU Emacs, because
most of the arguments listed in the backtrace are pointers to Lisp
objects. The numeric values of these pointers have no
significance whatever; all that matters is the contents of the
objects they point to (and most of the contents are themselves
pointers).
To provide useful information, you need to show the values of Lisp
objects in Lisp notation. Do this for each variable which is a
Lisp object, in several stack frames near the bottom of the stack.
Look at the source to see which variables are Lisp objects,
because the debugger thinks of them as integers.
To show a variable's value in Lisp syntax, first print its value,
then use the user-defined GDB command `pr' to print the Lisp
object in Lisp syntax. (If you must use another debugger, call
the function `debug_print' with the object as an argument.) The
`pr' command is defined by the file `.gdbinit', and it works only
if you are debugging a running process (not with a core dump).
To make Lisp errors stop Emacs and return to GDB, put a breakpoint
at `Fsignal'.
For a short listing of Lisp functions running, type the GDB
command `xbacktrace'.
The file `.gdbinit' defines several other commands that are useful
for examining the data types and contents of Lisp objects. Their
names begin with `x'. These commands work at a lower level than
`pr', and are less convenient, but they may work even when `pr'
does not, such as when debugging a core dump or when Emacs has had
a fatal signal.
More detailed advice and other useful techniques for debugging
Emacs are available in the file `etc/DEBUG' in the Emacs
distribution. That file also includes instructions for
investigating problems whereby Emacs stops responding (many people
assume that Emacs is "hung," whereas in fact it might be in an
infinite loop).
To find the file `etc/DEBUG' in your Emacs installation, use the
directory name stored in the variable `data-directory'.
Here are some things that are not necessary in a bug report:
* A description of the envelope of the bug--this is not necessary
for a reproducible bug.
Often people who encounter a bug spend a lot of time investigating
which changes to the input file will make the bug go away and which
changes will not affect it.
This is often time-consuming and not very useful, because the way
we will find the bug is by running a single example under the
debugger with breakpoints, not by pure deduction from a series of
examples. You might as well save time by not searching for
additional examples. It is better to send the bug report right
away, go back to editing, and find another bug to report.
Of course, if you can find a simpler example to report _instead_ of
the original one, that is a convenience. Errors in the output
will be easier to spot, running under the debugger will take less
time, etc.
However, simplification is not vital; if you can't do this or
don't have time to try, please report the bug with your original
test case.
* A core dump file.
Debugging the core dump might be useful, but it can only be done on
your machine, with your Emacs executable. Therefore, sending the
core dump file to the Emacs maintainers won't be useful. Above
all, don't include the core file in an email bug report! Such a
large message can be extremely inconvenient.
* A system-call trace of Emacs execution.
System-call traces are very useful for certain special kinds of
debugging, but in most cases they give little useful information.
It is therefore strange that many people seem to think that _the_
way to report information about a crash is to send a system-call
trace. Perhaps this is a habit formed from experience debugging
programs that don't have source code or debugging symbols.
In most programs, a backtrace is normally far, far more
informative than a system-call trace. Even in Emacs, a simple
backtrace is generally more informative, though to give full
information you should supplement the backtrace by displaying
variable values and printing them as Lisp objects with `pr' (see
above).
* A patch for the bug.
A patch for the bug is useful if it is a good one. But don't omit
the other information that a bug report needs, such as the test
case, on the assumption that a patch is sufficient. We might see
problems with your patch and decide to fix the problem another
way, or we might not understand it at all. And if we can't
understand what bug you are trying to fix, or why your patch
should be an improvement, we mustn't install it.
*Note Sending Patches::, for guidelines on how to make it easy for
us to understand and install your patches.
* A guess about what the bug is or what it depends on.
Such guesses are usually wrong. Even experts can't guess right
about such things without first using the debugger to find the
facts.
File: emacs, Node: Sending Patches, Prev: Checklist, Up: Bugs
Sending Patches for GNU Emacs
-----------------------------
If you would like to write bug fixes or improvements for GNU Emacs,
that is very helpful. When you send your changes, please follow these
guidelines to make it easy for the maintainers to use them. If you
don't follow these guidelines, your information might still be useful,
but using it will take extra work. Maintaining GNU Emacs is a lot of
work in the best of circumstances, and we can't keep up unless you do
your best to help.
* Send an explanation with your changes of what problem they fix or
what improvement they bring about. For a bug fix, just include a
copy of the bug report, and explain why the change fixes the bug.
(Referring to a bug report is not as good as including it, because
then we will have to look it up, and we have probably already
deleted it if we've already fixed the bug.)
* Always include a proper bug report for the problem you think you
have fixed. We need to convince ourselves that the change is
right before installing it. Even if it is correct, we might have
trouble understanding it if we don't have a way to reproduce the
problem.
* Include all the comments that are appropriate to help people
reading the source in the future understand why this change was
needed.
* Don't mix together changes made for different reasons. Send them
_individually_.
If you make two changes for separate reasons, then we might not
want to install them both. We might want to install just one. If
you send them all jumbled together in a single set of diffs, we
have to do extra work to disentangle them--to figure out which
parts of the change serve which purpose. If we don't have time
for this, we might have to ignore your changes entirely.
If you send each change as soon as you have written it, with its
own explanation, then two changes never get tangled up, and we can
consider each one properly without any extra work to disentangle
them.
* Send each change as soon as that change is finished. Sometimes
people think they are helping us by accumulating many changes to
send them all together. As explained above, this is absolutely
the worst thing you could do.
Since you should send each change separately, you might as well
send it right away. That gives us the option of installing it
immediately if it is important.
* Use `diff -c' to make your diffs. Diffs without context are hard
to install reliably. More than that, they are hard to study; we
must always study a patch to decide whether we want to install it.
Unidiff format is better than contextless diffs, but not as easy
to read as `-c' format.
If you have GNU diff, use `diff -c -F'^[_a-zA-Z0-9$]+ *('' when
making diffs of C code. This shows the name of the function that
each change occurs in.
* Avoid any ambiguity as to which is the old version and which is
the new. Please make the old version the first argument to diff,
and the new version the second argument. And please give one
version or the other a name that indicates whether it is the old
version or your new changed one.
* Write the change log entries for your changes. This is both to
save us the extra work of writing them, and to help explain your
changes so we can understand them.
The purpose of the change log is to show people where to find what
was changed. So you need to be specific about what functions you
changed; in large functions, it's often helpful to indicate where
within the function the change was.
On the other hand, once you have shown people where to find the
change, you need not explain its purpose in the change log. Thus,
if you add a new function, all you need to say about it is that it
is new. If you feel that the purpose needs explaining, it
probably does--but put the explanation in comments in the code.
It will be more useful there.
Please read the `ChangeLog' files in the `src' and `lisp'
directories to see what sorts of information to put in, and to
learn the style that we use. If you would like your name to
appear in the header line, showing who made the change, send us
the header line. *Note Change Log::.
* When you write the fix, keep in mind that we can't install a
change that would break other systems. Please think about what
effect your change will have if compiled on another type of system.
Sometimes people send fixes that _might_ be an improvement in
general--but it is hard to be sure of this. It's hard to install
such changes because we have to study them very carefully. Of
course, a good explanation of the reasoning by which you concluded
the change was correct can help convince us.
The safest changes are changes to the configuration files for a
particular machine. These are safe because they can't create new
bugs on other machines.
Please help us keep up with the workload by designing the patch in
a form that is clearly safe to install.
File: emacs, Node: Contributing, Next: Service, Prev: Bugs, Up: Top
Contributing to Emacs Development
=================================
If you would like to help pretest Emacs releases to assure they work
well, or if you would like to work on improving Emacs, please contact
the maintainers at <bug-gnu-emacs@gnu.org>. A pretester should be
prepared to investigate bugs as well as report them. If you'd like to
work on improving Emacs, please ask for suggested projects or suggest
your own ideas.
If you have already written an improvement, please tell us about it.
If you have not yet started work, it is useful to contact
<bug-gnu-emacs@gnu.org> before you start; it might be possible to
suggest ways to make your extension fit in better with the rest of
Emacs.
File: emacs, Node: Service, Next: Command Arguments, Prev: Contributing, Up: Top
How To Get Help with GNU Emacs
==============================
If you need help installing, using or changing GNU Emacs, there are
two ways to find it:
* Send a message to the mailing list <help-gnu-emacs@gnu.org>, or
post your request on newsgroup `gnu.emacs.help'. (This mailing
list and newsgroup interconnect, so it does not matter which one
you use.)
* Look in the service directory for someone who might help you for a
fee. The service directory is found in the file named
`etc/SERVICE' in the Emacs distribution.
File: emacs, Node: Command Arguments, Next: Antinews, Prev: Service, Up: Top
Command Line Arguments
**********************
GNU Emacs supports command line arguments to request various actions
when invoking Emacs. These are for compatibility with other editors and
for sophisticated activities. We don't recommend using them for
ordinary editing.
Arguments starting with `-' are "options". Other arguments specify
files to visit. Emacs visits the specified files while it starts up.
The last file name on your command line becomes the current buffer; the
other files are also visited in other buffers. If there are two files,
they are both displayed; otherwise the last file is displayed along
with a buffer list that shows what other buffers there are. As with
most programs, the special argument `--' says that all subsequent
arguments are file names, not options, even if they start with `-'.
Emacs command options can specify many things, such as the size and
position of the X window Emacs uses, its colors, and so on. A few
options support advanced usage, such as running Lisp functions on files
in batch mode. The sections of this chapter describe the available
options, arranged according to their purpose.
There are two ways of writing options: the short forms that start
with a single `-', and the long forms that start with `--'. For
example, `-d' is a short form and `--display' is the corresponding long
form.
The long forms with `--' are easier to remember, but longer to type.
However, you don't have to spell out the whole option name; any
unambiguous abbreviation is enough. When a long option takes an
argument, you can use either a space or an equal sign to separate the
option name and the argument. Thus, you can write either `--display
sugar-bombs:0.0' or `--display=sugar-bombs:0.0'. We recommend an equal
sign because it makes the relationship clearer, and the tables below
always show an equal sign.
Most options specify how to initialize Emacs, or set parameters for
the Emacs session. We call them "initial options". A few options
specify things to do: for example, load libraries, call functions, or
terminate Emacs. These are called "action options". These and file
names together are called "action arguments". Emacs processes all the
action arguments in the order they are written.
* Menu:
* Action Arguments:: Arguments to visit files, load libraries,
and call functions.
* Initial Options:: Arguments that take effect while starting Emacs.
* Command Example:: Examples of using command line arguments.
* Resume Arguments:: Specifying arguments when you resume a running Emacs.
* Environment:: Environment variables that Emacs uses.
* Display X:: Changing the default display and using remote login.
* Font X:: Choosing a font for text, under X.
* Colors X:: Choosing colors, under X.
* Window Size X:: Start-up window size, under X.
* Borders X:: Internal and external borders, under X.
* Title X:: Specifying the initial frame's title.
* Icons X:: Choosing what sort of icon to use, under X.
* Resources X:: Advanced use of classes and resources, under X.
* Lucid Resources:: X resources for Lucid menus.
* LessTif Resources:: X resources for LessTif and Motif menus.
File: emacs, Node: Action Arguments, Next: Initial Options, Up: Command Arguments
Action Arguments
================
Here is a table of the action arguments and options:
`FILE'
`--visit=FILE'
`--file=FILE'
Visit FILE using `find-file'. *Note Visiting::.
`+LINENUM FILE'
Visit FILE using `find-file', then go to line number LINENUM in it.
`+LINENUM:COLUMNNUM FILE'
Visit FILE using `find-file', then go to line number LINENUM and
put point at column number COLUMNNUM.
`-l FILE'
`--load=FILE'
Load a Lisp library named FILE with the function `load'. *Note
Lisp Libraries::. The library can be found either in the current
directory, or in the Emacs library search path as specified with
`EMACSLOADPATH' (*note General Variables::).
`-f FUNCTION'
`--funcall=FUNCTION'
Call Lisp function FUNCTION with no arguments.
`--eval=EXPRESSION'
`--execute=EXPRESSION'
Evaluate Lisp expression EXPRESSION.
`--insert=FILE'
Insert the contents of FILE into the current buffer. This is like
what `M-x insert-file' does. *Note Misc File Ops::.
`--kill'
Exit from Emacs without asking for confirmation.
The init file can access the values of the action arguments as the
elements of a list in the variable `command-line-args'. The init file
can override the normal processing of the action arguments, or define
new ones, by reading and setting this variable.
File: emacs, Node: Initial Options, Next: Command Example, Prev: Action Arguments, Up: Command Arguments
Initial Options
===============
The initial options specify parameters for the Emacs session. This
section describes the more general initial options; some other options
specifically related to the X Window System appear in the following
sections.
Some initial options affect the loading of init files. The normal
actions of Emacs are to first load `site-start.el' if it exists, then
your own init file `~/.emacs' if it exists, and finally `default.el' if
it exists; certain options prevent loading of some of these files or
substitute other files for them.
`-t DEVICE'
`--terminal=DEVICE'
Use DEVICE as the device for terminal input and output.
`-d DISPLAY'
`--display=DISPLAY'
Use the X Window System and use the display named DISPLAY to open
the initial Emacs frame. *Note Display X::, for more details.
`-nw'
`--no-windows'
Don't communicate directly with the window system, disregarding the
`DISPLAY' environment variable even if it is set. This forces
Emacs to run as if the display were a text-only terminal.
`-batch'
`--batch'
Run Emacs in "batch mode", which means that the text being edited
is not displayed and the standard terminal interrupt characters
such as `C-z' and `C-c' continue to have their normal effect.
Emacs in batch mode outputs to `stderr' only what would normally
be displayed in the echo area under program control, and functions
which would normally read from the minibuffer take their input
from `stdin'.
Batch mode is used for running programs written in Emacs Lisp from
shell scripts, makefiles, and so on. Normally the `-l' option or
`-f' option will be used as well, to invoke a Lisp program to do
the batch processing.
`-batch' implies `-q' (do not load an init file). It also causes
Emacs to exit after processing all the command options. In
addition, it disables auto-saving except in buffers for which it
has been explicitly requested.
`-q'
`--no-init-file'
Do not load your Emacs init file `~/.emacs', or `default.el'
either. When invoked like this, Emacs does not allow saving
options changed with the `M-x customize' command and its variants.
*Note Easy Customization::.
`--no-site-file'
Do not load `site-start.el'. The options `-q', `-u' and `-batch'
have no effect on the loading of this file--this is the only
option that blocks it.
`-u USER'
`--user=USER'
Load USER's Emacs init file `~USER/.emacs' instead of your own.
`--debug-init'
Enable the Emacs Lisp debugger for errors in the init file.
`--unibyte'
Do almost everything with single-byte buffers and strings. All
buffers and strings are unibyte unless you (or a Lisp program)
explicitly ask for a multibyte buffer or string. (Note that Emacs
always loads Lisp files in multibyte mode, even if `--unibyte' is
specified; see *Note Enabling Multibyte::.) Setting the
environment variable `EMACS_UNIBYTE' has the same effect.
`--multibyte'
Inhibit the effect of `EMACS_UNIBYTE', so that Emacs uses
multibyte characters by default, as usual.
File: emacs, Node: Command Example, Next: Resume Arguments, Prev: Initial Options, Up: Command Arguments
Command Argument Example
========================
Here is an example of using Emacs with arguments and options. It
assumes you have a Lisp program file called `hack-c.el' which, when
loaded, performs some useful operation on the current buffer, expected
to be a C program.
emacs -batch foo.c -l hack-c -f save-buffer >& log
This says to visit `foo.c', load `hack-c.el' (which makes changes in
the visited file), save `foo.c' (note that `save-buffer' is the
function that `C-x C-s' is bound to), and then exit back to the shell
(because of `-batch'). `-batch' also guarantees there will be no
problem redirecting output to `log', because Emacs will not assume that
it has a display terminal to work with.
File: emacs, Node: Resume Arguments, Next: Environment, Prev: Command Example, Up: Command Arguments
Resuming Emacs with Arguments
=============================
You can specify action arguments for Emacs when you resume it after
a suspension. To prepare for this, put the following code in your
`.emacs' file (*note Hooks::):
(add-hook 'suspend-hook 'resume-suspend-hook)
(add-hook 'suspend-resume-hook 'resume-process-args)
As further preparation, you must execute the shell script
`emacs.csh' (if you use csh as your shell) or `emacs.bash' (if you use
bash as your shell). These scripts define an alias named `edit', which
will resume Emacs giving it new command line arguments such as files to
visit. The scripts are found in the `etc' subdirectory of the Emacs
distribution.
Only action arguments work properly when you resume Emacs. Initial
arguments are not recognized--it's too late to execute them anyway.
Note that resuming Emacs (with or without arguments) must be done
from within the shell that is the parent of the Emacs job. This is why
`edit' is an alias rather than a program or a shell script. It is not
possible to implement a resumption command that could be run from other
subjobs of the shell; there is no way to define a command that could be
made the value of `EDITOR', for example. Therefore, this feature does
not take the place of the Emacs Server feature (*note Emacs Server::).
The aliases use the Emacs Server feature if you appear to have a
server Emacs running. However, they cannot determine this with complete
accuracy. They may think that a server is still running when in
actuality you have killed that Emacs, because the file `/tmp/esrv...'
still exists. If this happens, find that file and delete it.
File: emacs, Node: Environment, Next: Display X, Prev: Resume Arguments, Up: Command Arguments
Environment Variables
=====================
The "environment" is a feature of the operating system; it consists
of a collection of variables with names and values. Each variable is
called an "environment variable"; environment variable names are
case-sensitive, and it is conventional to use upper case letters only.
The values are all text strings.
What makes the environment useful is that subprocesses inherit the
environment automatically from their parent process. This means you
can set up an environment variable in your login shell, and all the
programs you run (including Emacs) will automatically see it.
Subprocesses of Emacs (such as shells, compilers, and version-control
software) inherit the environment from Emacs, too.
Inside Emacs, the command `M-x getenv' gets the value of an
environment variable. `M-x setenv' sets a variable in the Emacs
environment. The way to set environment variables outside of Emacs
depends on the operating system, and especially the shell that you are
using. For example, here's how to set the environment variable
`ORGANIZATION' to `not very much' using Bash:
export ORGANIZATION="not very much"
and here's how to do it in csh or tcsh:
setenv ORGANIZATION "not very much"
When Emacs is uses the X Window System, it inherits the use of a
large number of environment variables from the X libraries. See the X
documentation for more information.
* Menu:
* General Variables:: Environment variables that all versions of Emacs use.
* Misc Variables:: Certain system-specific variables.