4.4BSD/usr/src/contrib/emacs-18.57/info/emacs-8

Info file ../info/emacs, produced by Makeinfo, -*- Text -*- from
input file emacs.tex.

This file documents the GNU Emacs editor.

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the sections entitled "The GNU Manifesto", "Distribution" and
"GNU General Public License" are included exactly as in the original,
and provided that the entire resulting derived work is distributed
under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the sections entitled "The GNU Manifesto",
"Distribution" and "GNU General Public License" may be included in a
translation approved by the author instead of in the original English.

File: emacs, Node: Documentation, Next: Change Log, Prev: Lisp Completion, Up: Programs

Documentation Commands
======================

As you edit Lisp code to be run in Emacs, the commands `C-h f'
(`describe-function') and `C-h v' (`describe-variable') can be used
to print documentation of functions and variables that you want to
call. These commands use the minibuffer to read the name of a
function or variable to document, and display the documentation in a
window.

For extra convenience, these commands provide default arguments based
on the code in the neighborhood of point. `C-h f' sets the default
to the function called in the innermost list containing point. `C-h
v' uses the symbol name around or adjacent to point as its default.

Documentation on Unix commands, system calls and libraries can be
obtained with the `M-x manual-entry' command. This reads a topic as
an argument, and displays the text on that topic from the Unix manual.
`manual-entry' always searches all 8 sections of the manual, and
concatenates all the entries that are found. For example, the topic
`termcap' finds the description of the termcap library from section
3, followed by the description of the termcap data base from section 5.

File: emacs, Node: Change Log, Next: Tags, Prev: Documentation, Up: Programs

Change Logs
===========

The Emacs command `M-x add-change-log-entry' helps you keep a record
of when and why you have changed a program. It assumes that you have
a file in which you write a chronological sequence of entries
describing individual changes. The default is to store the change
entries in a file called `ChangeLog' in the same directory as the
file you are editing. The same `ChangeLog' file therefore records
changes for all the files in the directory.

A change log entry starts with a header line that contains your name
and the current date. Aside from these header lines, every line in
the change log starts with a tab. One entry can describe several
changes; each change starts with a line starting with a tab and a
star. `M-x add-change-log-entry' visits the change log file and
creates a new entry unless the most recent entry is for today's date
and your name. In either case, it adds a new line to start the
description of another change just after the header line of the
entry. When `M-x add-change-log-entry' is finished, all is prepared
for you to edit in the description of what you changed and how. You
must then save the change log file yourself.

The change log file is always visited in Indented Text mode, which
means that LFD and auto-filling indent each new line like the
previous line. This is convenient for entering the contents of an
entry, which must all be indented. *Note Text Mode::.

Here is an example of the formatting conventions used in the change
log for Emacs:

Wed Jun 26 19:29:32 1985 Richard M. Stallman (rms at mit-prep)

* xdisp.c (try_window_id):
If C-k is done at end of next-to-last line,
this fn updates window_end_vpos and cannot leave
window_end_pos nonnegative (it is zero, in fact).
If display is preempted before lines are output,
this is inconsistent. Fix by setting
blank_end_of_window to nonzero.

Tue Jun 25 05:25:33 1985 Richard M. Stallman (rms at mit-prep)

* cmds.c (Fnewline):
Call the auto fill hook if appropriate.

* xdisp.c (try_window_id):
If point is found by compute_motion after xp, record that
permanently. If display_text_line sets point position wrong
(case where line is killed, point is at eob and that line is
not displayed), set it again in final compute_motion.

File: emacs, Node: Tags, Next: Fortran, Prev: Change Log, Up: Programs

Tag Tables
==========

A "tag table" is a description of how a multi-file program is broken
up into files. It lists the names of the component files and the
names and positions of the functions in each file. Grouping the
related files makes it possible to search or replace through all the
files with one command. Recording the function names and positions
makes possible the `Meta-.' command which you can use to find the
definition of a function without having to know which of the files it
is in.

Tag tables are stored in files called "tag table files". The
conventional name for a tag table file is `TAGS'.

Each entry in the tag table records the name of one tag, the name of
the file that the tag is defined in (implicitly), and the position in
that file of the tag's definition.

Just what names from the described files are recorded in the tag
table depends on the programming language of the described file.
They normally include all functions and subroutines, and may also
include global variables, data types, and anything else convenient.
In any case, each name recorded is called a "tag".

* Menu:

* Tag Syntax::
* Create Tag Table::
* Select Tag Table::
* Find Tag::
* Tags Search::
* Tags Stepping::
* List Tags::

File: emacs, Node: Tag Syntax, Next: Create Tag Table, Prev: Tags, Up: Tags

Source File Tag Syntax
----------------------

In Lisp code, any function defined with `defun', any variable defined
with `defvar' or `defconst', and in general the first argument of any
expression that starts with `(def' in column zero, is a tag.

In C code, any C function is a tag, and so is any typedef if `-t' is
specified when the tag table is constructed.

In Fortran code, functions and subroutines are tags.

In LaTeX text, the argument of any of the commands `\chapter',
`\section', `\subsection', `\subsubsection', `\eqno', `\label',
`\ref', `\cite', `\bibitem' and `\typeout' is a tag.

File: emacs, Node: Create Tag Table, Next: Select Tag Table, Prev: Tag Syntax, Up: Tags

Creating Tag Tables
-------------------

The `etags' program is used to create a tag table file. It knows the
syntax of C, Fortran, LaTeX, Scheme and Emacs Lisp/Common Lisp. To
use `etags', type

etags INPUTFILES...

as a shell command. It reads the specified files and writes a tag
table named `TAGS' in the current working directory. `etags'
recognizes the language used in an input file based on its file name
and contents; there are no switches for specifying the language. The
`-t' switch tells `etags' to record typedefs in C code as tags.

If the tag table data become outdated due to changes in the files
described in the table, the way to update the tag table is the same
way it was made in the first place. It is not necessary to do this
often.

If the tag table fails to record a tag, or records it for the wrong
file, then Emacs cannot possibly find its definition. However, if
the position recorded in the tag table becomes a little bit wrong
(due to some editing in the file that the tag definition is in), the
only consequence is to slow down finding the tag slightly. Even if
the stored position is very wrong, Emacs will still find the tag, but
it must search the entire file for it.

So you should update a tag table when you define new tags that you
want to have listed, or when you move tag definitions from one file
to another, or when changes become substantial. Normally there is no
need to update the tag table after each edit, or even every day.

File: emacs, Node: Select Tag Table, Next: Find Tag, Prev: Create Tag Table, Up: Tags

Selecting a Tag Table
---------------------

Emacs has at any time one "selected" tag table, and all the commands
for working with tag tables use the selected one. To select a tag
table, type `M-x visit-tags-table', which reads the tag table file
name as an argument. The name `TAGS' in the default directory is
used as the default file name.

All this command does is store the file name in the variable
`tags-file-name'. Emacs does not actually read in the tag table
contents until you try to use them. Setting this variable yourself
is just as good as using `visit-tags-table'. The variable's initial
value is `nil'; this value tells all the commands for working with
tag tables that they must ask for a tag table file name to use.

File: emacs, Node: Find Tag, Next: Tags Search, Prev: Select Tag Table, Up: Tags

Finding a Tag
-------------

The most important thing that a tag table enables you to do is to
find the definition of a specific tag.

`M-. TAG'
Find first definition of TAG (`find-tag').

`C-u M-.'
Find next alternate definition of last tag specified.

`C-x 4 . TAG'
Find first definition of TAG, but display it in another window
(`find-tag-other-window').

`M-.' (`find-tag') is the command to find the definition of a
specified tag. It searches through the tag table for that tag, as a
string, and then uses the tag table info to determine the file that
the definition is in and the approximate character position in the
file of the definition. Then `find-tag' visits that file, moves
point to the approximate character position, and starts searching
ever-increasing distances away for the the text that should appear at
the beginning of the definition.

If an empty argument is given (just type RET), the sexp in the buffer
before or around point is used as the name of the tag to find. *Note
Lists::, for info on sexps.

The argument to `find-tag' need not be the whole tag name; it can be
a substring of a tag name. However, there can be many tag names
containing the substring you specify. Since `find-tag' works by
searching the text of the tag table, it finds the first tag in the
table that the specified substring appears in. The way to find other
tags that match the substring is to give `find-tag' a numeric
argument, as in `C-u M-.'; this does not read a tag name, but
continues searching the tag table's text for another tag containing
the same substring last used. If you have a real META key, `M-0 M-.'
is an easier alternative to `C-u M-.'.

Like most commands that can switch buffers, `find-tag' has another
similar command that displays the new buffer in another window. `C-x
4 .' invokes the function `find-tag-other-window'. (This key
sequence ends with a period.)

Emacs comes with a tag table file `TAGS', in the directory containing
Lisp libraries, which includes all the Lisp libraries and all the C
sources of Emacs. By specifying this file with `visit-tags-table'
and then using `M-.' you can quickly look at the source of any Emacs
function.

File: emacs, Node: Tags Search, Next: Tags Stepping, Prev: Find Tag, Up: Tags

Searching and Replacing with Tag Tables
---------------------------------------

The commands in this section visit and search all the files listed in
the selected tag table, one by one. For these commands, the tag
table serves only to specify a sequence of files to search. A
related command is `M-x grep' (*note Compilation::.).

`M-x tags-search'
Search for the specified regexp through the files in the
selected tag table.

`M-x tags-query-replace'
Perform a `query-replace' on each file in the selected tag table.

`M-,'
Restart one of the commands above, from the current location of
point (`tags-loop-continue').

`M-x tags-search' reads a regexp using the minibuffer, then visits
the files of the selected tag table one by one, and searches through
each one for that regexp. It displays the name of the file being
searched so you can follow its progress. As soon as an occurrence is
found, `tags-search' returns.

Having found one match, you probably want to find all the rest. To
find one more match, type `M-,' (`tags-loop-continue') to resume the
`tags-search'. This searches the rest of the current buffer,
followed by the remaining files of the tag table.

`M-x tags-query-replace' performs a single `query-replace' through
all the files in the tag table. It reads a string to search for and
a string to replace with, just like ordinary `M-x query-replace'. It
searches much like `M-x tags-search' but repeatedly, processing
matches according to your input. *Note Replace::, for more
information on `query-replace'.

It is possible to get through all the files in the tag table with a
single invocation of `M-x tags-query-replace'. But since any
unrecognized character causes the command to exit, you may need to
continue where you left off. `M-,' can be used for this. It resumes
the last tags search or replace command that you did.

It may have struck you that `tags-search' is a lot like `grep'. You
can also run `grep' itself as an inferior of Emacs and have Emacs
show you the matching lines one by one. This works mostly the same
as running a compilation and having Emacs show you where the errors
were. *Note Compilation::.

File: emacs, Node: Tags Stepping, Next: List Tags, Prev: Tags Search, Up: Tags

Stepping Through a Tag Table
----------------------------

If you wish to process all the files in the selected tag table, but
`M-x tags-search' and `M-x tags-query-replace' in particular are not
what you want, you can use `M-x next-file'.

`C-u M-x next-file'
With a numeric argument, regardless of its value, visit the
first file in the tag table, and prepare to advance sequentially
by files.

`M-x next-file'
Visit the next file in the selected tag table.

File: emacs, Node: List Tags, Prev: Tags Stepping, Up: Tags

Tag Table Inquiries
-------------------

`M-x list-tags'
Display a list of the tags defined in a specific program file.

`M-x tags-apropos'
Display a list of all tags matching a specified regexp.

`M-x list-tags' reads the name of one of the files described by the
selected tag table, and displays a list of all the tags defined in
that file. The "file name" argument is really just a string to
compare against the names recorded in the tag table; it is read as a
string rather than as a file name. Therefore, completion and
defaulting are not available, and you must enter the string the same
way it appears in the tag table. Do not include a directory as part
of the file name unless the file name recorded in the tag table
includes a directory.

`M-x tags-apropos' is like `apropos' for tags. It reads a regexp,
then finds all the tags in the selected tag table whose entries match
that regexp, and displays the tag names found.

File: emacs, Node: Fortran, Prev: Tags, Up: Programs

Fortran Mode
============

Fortran mode provides special motion commands for Fortran statements
and subprograms, and indentation commands that understand Fortran
conventions of nesting, line numbers and continuation statements.

Special commands for comments are provided because Fortran comments
are unlike those of other languages.

Built-in abbrevs optionally save typing when you insert Fortran
keywords.

Use `M-x fortran-mode' to switch to this major mode. Doing so calls
the value of `fortran-mode-hook' as a function of no arguments if
that variable has a value that is not `nil'.

* Menu:

* Motion: Fortran Motion. Moving point by statements or subprograms.
* Indent: Fortran Indent. Indentation commands for Fortran.
* Comments: Fortran Comments. Inserting and aligning comments.
* Columns: Fortran Columns. Measuring columns for valid Fortran.
* Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords.

Fortran mode was contributed by Michael Prange.

File: emacs, Node: Fortran Motion, Next: Fortran Indent, Prev: Fortran, Up: Fortran

Motion Commands
---------------

Fortran mode provides special commands to move by subprograms
(functions and subroutines) and by statements. There is also a
command to put the region around one subprogram, convenient for
killing it or moving it.

`C-M-a'
Move to beginning of subprogram
(`beginning-of-fortran-subprogram').

`C-M-e'
Move to end of subprogram (`end-of-fortran-subprogram').

`C-M-h'
Put point at beginning of subprogram and mark at end
(`mark-fortran-subprogram').

`C-c C-n'
Move to beginning of current or next statement
(`fortran-next-statement').

`C-c C-p'
Move to beginning of current or previous statement
(`fortran-previous-statement').

File: emacs, Node: Fortran Indent, Next: Fortran Comments, Prev: Fortran Motion, Up: Fortran

Fortran Indentation
-------------------

Special commands and features are needed for indenting Fortran code
in order to make sure various syntactic entities (line numbers,
comment line indicators and continuation line flags) appear in the
columns that are required for standard Fortran.

* Menu:

* Commands: ForIndent Commands. Commands for indenting Fortran.
* Numbers: ForIndent Num. How line numbers auto-indent.
* Conv: ForIndent Conv. Conventions you must obey to avoid trouble.
* Vars: ForIndent Vars. Variables controlling Fortran indent style.

File: emacs, Node: ForIndent Commands, Next: ForIndent Num, Prev: Fortran Indent, Up: Fortran Indent

Fortran Indentation Commands
............................

`TAB'
Indent the current line (`fortran-indent-line').

`M-LFD'
Break the current line and set up a continuation line.

`C-M-q'
Indent all the lines of the subprogram point is in
(`fortran-indent-subprogram').

TAB is redefined by Fortran mode to reindent the current line for
Fortran (`fortran-indent-line'). Line numbers and continuation
markers are indented to their required columns, and the body of the
statement is independently indented based on its nesting in the
program.

The key `C-M-q' is redefined as `fortran-indent-subprogram', a
command to reindent all the lines of the Fortran subprogram (function
or subroutine) containing point.

The key `M-LFD' is redefined as `fortran-split-line', a command to
split a line in the appropriate fashion for Fortran. In a
non-comment line, the second half becomes a continuation line and is
indented accordingly. In a comment line, both halves become separate
comment lines.

File: emacs, Node: ForIndent Num, Next: ForIndent Conv, Prev: ForIndent Commands, Up: Fortran Indent

Line Numbers and Continuation
.............................

If a number is the first non-whitespace in the line, it is assumed to
be a line number and is moved to columns 0 through 4. (Columns are
always counted from 0 in GNU Emacs.) If the text on the line starts
with the conventional Fortran continuation marker `$', it is moved to
column 5. If the text begins with any non whitespace character in
column 5, it is assumed to be an unconventional continuation marker
and remains in column 5.

Line numbers of four digits or less are normally indented one space.
This amount is controlled by the variable
`fortran-line-number-indent' which is the maximum indentation a line
number can have. Line numbers are indented to right-justify them to
end in column 4 unless that would require more than this maximum
indentation. The default value of the variable is 1.

Simply inserting a line number is enough to indent it according to
these rules. As each digit is inserted, the indentation is
recomputed. To turn off this feature, set the variable
`fortran-electric-line-number' to `nil'. Then inserting line numbers
is like inserting anything else.

File: emacs, Node: ForIndent Conv, Next: ForIndent Vars, Prev: ForIndent Num, Up: Fortran Indent

Syntactic Conventions
.....................

Fortran mode assumes that you follow certain conventions that
simplify the task of understanding a Fortran program well enough to
indent it properly:

* Two nested `do' loops never share a `continue' statement.

* The same character appears in column 5 of all continuation
lines, and this character is the value of the variable
`fortran-continuation-char'. By default, this character is `$'.

If you fail to follow these conventions, the indentation commands may
indent some lines unaesthetically. However, a correct Fortran
program will retain its meaning when reindented even if the
conventions are not followed.

File: emacs, Node: ForIndent Vars, Prev: ForIndent Conv, Up: Fortran Indent

Variables for Fortran Indentation
.................................

Several additional variables control how Fortran indentation works.

`fortran-do-indent'
Extra indentation within each level of `do' statement (default 3).

`fortran-if-indent'
Extra indentation within each level of `if' statement (default 3).

`fortran-continuation-indent'
Extra indentation for bodies of continuation lines (default 5).

`fortran-check-all-num-for-matching-do'
If this is `nil', indentation assumes that each `do' statement
ends on a `continue' statement. Therefore, when computing
indentation for a statement other than `continue', it can save
time by not checking for a `do' statement ending there. If this
is non-`nil', indenting any numbered statement must check for a
`do' that ends there. The default is `nil'.

`fortran-minimum-statement-indent'
Minimum indentation for fortran statements. For standard
Fortran, this is 6. Statement bodies will never be indented
less than this much.

File: emacs, Node: Fortran Comments, Next: Fortran Columns, Prev: Fortran Indent, Up: Fortran

Comments
--------

The usual Emacs comment commands assume that a comment can follow a
line of code. In Fortran, the standard comment syntax requires an
entire line to be just a comment. Therefore, Fortran mode replaces
the standard Emacs comment commands and defines some new variables.

Fortran mode can also handle a nonstandard comment syntax where
comments start with `!' and can follow other text. Because only some
Fortran compilers accept this syntax, Fortran mode will not insert
such comments unless you have said in advance to do so. To do this,
set the variable `comment-start' to `"!"' (*note Variables::.).

`M-;'
Align comment or insert new comment (`fortran-comment-indent').

`C-x ;'
Applies to nonstandard `!' comments only.

`C-c ;'
Turn all lines of the region into comments, or (with arg) turn
them back into real code (`fortran-comment-region').

`M-;' in Fortran mode is redefined as the command
`fortran-comment-indent'. Like the usual `M-;' command, this
recognizes any kind of existing comment and aligns its text
appropriately; if there is no existing comment, a comment is inserted
and aligned. But inserting and aligning comments are not the same in
Fortran mode as in other modes.

When a new comment must be inserted, if the current line is blank, a
full-line comment is inserted. On a non-blank line, a nonstandard
`!' comment is inserted if you have said you want to use them.
Otherwise a full-line comment is inserted on a new line before the
current line.

Nonstandard `!' comments are aligned like comments in other
languages, but full-line comments are different. In a standard
full-line comment, the comment delimiter itself must always appear in
column zero. What can be aligned is the text within the comment.
You can choose from three styles of alignment by setting the variable
`fortran-comment-indent-style' to one of these values:

`fixed'
The text is aligned at a fixed column, which is the value of
`fortran-comment-line-column'. This is the default.

`relative'
The text is aligned as if it were a line of code, but with an
additional `fortran-comment-line-column' columns of indentation.

`nil'
Text in full-line columns is not moved automatically.

In addition, you can specify the character to be used to indent
within full-line comments by setting the variable
`fortran-comment-indent-char' to the character you want to use.

Fortran mode introduces two variables `comment-line-start' and
`comment-line-start-skip' which play for full-line comments the same
roles played by `comment-start' and `comment-start-skip' for ordinary
text-following comments. Normally these are set properly by Fortran
mode so you do not need to change them.

The normal Emacs comment command `C-x ;' has not been redefined. If
you use `!' comments, this command can be used with them. Otherwise
it is useless in Fortran mode.

The command `C-c ;' (`fortran-comment-region') turns all the lines of
the region into comments by inserting the string `C$$$' at the front
of each one. With a numeric arg, the region is turned back into live
code by deleting `C$$$' from the front of each line in it. The
string used for these comments can be controlled by setting the
variable `fortran-comment-region'. Note that here we have an example
of a command and a variable with the same name; these two uses of the
name never conflict because in Lisp and in Emacs it is always clear
from the context which one is meant.

File: emacs, Node: Fortran Columns, Next: Fortran Abbrev, Prev: Fortran Comments, Up: Fortran

Columns
-------

`C-c C-r'
Displays a "column ruler" momentarily above the current line
(`fortran-column-ruler').

`C-c C-w'
Splits the current window horizontally so that it is 72 columns
wide. This may help you avoid going over that limit
(`fortran-window-create').

The command `C-c C-r' (`fortran-column-ruler') shows a column ruler
momentarily above the current line. The comment ruler is two lines
of text that show you the locations of columns with special
significance in Fortran programs. Square brackets show the limits of
the columns for line numbers, and curly brackets show the limits of
the columns for the statement body. Column numbers appear above them.

Note that the column numbers count from zero, as always in GNU Emacs.
As a result, the numbers may not be those you are familiar with; but
the actual positions in the line are standard Fortran.

The text used to display the column ruler is the value of the
variable `fortran-comment-ruler'. By changing this variable, you can
change the display.

For even more help, use `C-c C-w' (`fortran-window-create'), a
command which splits the current window horizontally, making a window
72 columns wide. By editing in this window you can immediately see
when you make a line too wide to be correct Fortran.

File: emacs, Node: Fortran Abbrev, Prev: Fortran Columns, Up: Fortran

Fortran Keyword Abbrevs
-----------------------

Fortran mode provides many built-in abbrevs for common keywords and
declarations. These are the same sort of abbrev that you can define
yourself. To use them, you must turn on Abbrev mode. *note
Abbrevs::..

The built-in abbrevs are unusual in one way: they all start with a
semicolon. You cannot normally use semicolon in an abbrev, but
Fortran mode makes this possible by changing the syntax of semicolon
to "word constituent".

For example, one built-in Fortran abbrev is `;c' for `continue'. If
you insert `;c' and then insert a punctuation character such as a
space or a newline, the `;c' will change automatically to `continue',
provided Abbrev mode is enabled.

Type `;?' or `;C-h' to display a list of all the built-in Fortran
abbrevs and what they stand for.

File: emacs, Node: Running, Next: Abbrevs, Prev: Programs, Up: Top

Compiling and Testing Programs
******************************

The previous chapter discusses the Emacs commands that are useful for
making changes in programs. This chapter deals with commands that
assist in the larger process of developing and maintaining programs.

* Menu:

* Compilation:: Compiling programs in languages other than Lisp
(C, Pascal, etc.)
* Modes: Lisp Modes. Various modes for editing Lisp programs, with
different facilities for running the Lisp programs.
* Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs.
* Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer.
* Eval: Lisp Eval. Executing a single Lisp expression in Emacs.
* Debug: Lisp Debug. Debugging Lisp programs running in Emacs.
* External Lisp:: Communicating through Emacs with a separate Lisp.

File: emacs, Node: Compilation, Next: Lisp Modes, Prev: Running, Up: Running

Running `make', or Compilers Generally
======================================

Emacs can run compilers for noninteractive languages such as C and
Fortran as inferior processes, feeding the error log into an Emacs
buffer. It can also parse the error messages and visit the files in
which errors are found, moving point right to the line where the
error occurred.

`M-x compile'
Run a compiler asynchronously under Emacs, with error messages
to `*compilation*' buffer.

`M-x grep'
Run `grep' asynchronously under Emacs, with matching lines
listed in the buffer named `*compilation*'.

`M-x kill-compiler'
`M-x kill-grep'
Kill the running compilation or `grep' subprocess.

`C-x `'
Visit the locus of the next compiler error message or `grep'
match.

To run `make' or another compiler, do `M-x compile'. This command
reads a shell command line using the minibuffer, and then executes
the specified command line in an inferior shell with output going to
the buffer named `*compilation*'. The current buffer's default
directory is used as the working directory for the execution of the
command; normally, therefore, the makefile comes from this directory.

When the shell command line is read, the minibuffer appears
containing a default command line, which is the command you used the
last time you did `M-x compile'. If you type just RET, the same
command line is used again. The first `M-x compile' provides `make
-k' as the default. The default is taken from the variable
`compile-command'; if the appropriate compilation command for a file
is something other than `make -k', it can be useful to have the file
specify a local value for `compile-command' (*note File Variables::.).

Starting a compilation causes the buffer `*compilation*' to be
displayed in another window but not selected. Its mode line tells
you whether compilation is finished, with the word `run' or `exit'
inside the parentheses. You do not have to keep this buffer visible;
compilation continues in any case.

To kill the compilation process, do `M-x kill-compilation'. You will
see that the mode line of the `*compilation*' buffer changes to say
`signal' instead of `run'. Starting a new compilation also kills any
running compilation, as only one can exist at any time. However,
this requires confirmation before actually killing a compilation that
is running.

To parse the compiler error messages, type `C-x `' (`next-error').
The character following the `C-x' is the grave accent, not the single
quote. This command displays the buffer `*compilation*' in one
window and the buffer in which the next error occurred in another
window. Point in that buffer is moved to the line where the error
was found. The corresponding error message is scrolled to the top of
the window in which `*compilation*' is displayed.

The first time `C-x `' is used after the start of a compilation, it
parses all the error messages, visits all the files that have error
messages, and makes markers pointing at the lines that the error
messages refer to. Then it moves to the first error message
location. Subsequent uses of `C-x `' advance down the data set up by
the first use. When the preparsed error messages are exhausted, the
next `C-x `' checks for any more error messages that have come in;
this is useful if you start editing the compiler errors while the
compilation is still going on. If no more error messages have come
in, `C-x `' reports an error.

`C-u C-x `' discards the preparsed error message data and parses the
`*compilation*' buffer over again, then displaying the first error.
This way, you can process the same set of errors again.

Instead of running a compiler, you can run `grep' and see the lines
on which matches were found. To do this, type `M-x grep' with an
argument line that contains the same arguments you would give `grep'
when running it normally: a `grep'-style regexp (usually in
singlequotes to quote the shell's special characters) followed by
filenames which may use wildcards. The output from `grep' goes in
the `*compilation*' buffer and the lines that matched can be found
with `C-x `' as if they were compilation errors.

Note: a shell is used to run the compile command, but the shell is
told that it should be noninteractive. This means in particular that
the shell starts up with no prompt. If you find your usual shell
prompt making an unsightly appearance in the `*compilation*' buffer,
it means you have made a mistake in your shell's init file (`.cshrc'
or `.shrc' or ...) by setting the prompt unconditionally. The shell
init file should set the prompt only if there already is a prompt.
In `csh', here is how to do it:

if ($?prompt) set prompt = ...

File: emacs, Node: Lisp Modes, Next: Lisp Libraries, Prev: Compilation, Up: Running

Major Modes for Lisp
====================

Emacs has four different major modes for Lisp. They are the same in
terms of editing commands, but differ in the commands for executing
Lisp expressions.

Emacs-Lisp mode
The mode for editing source files of programs to run in Emacs
Lisp. This mode defines `C-M-x' to evaluate the current defun.
*Note Lisp Libraries::.

Lisp Interaction mode
The mode for an interactive session with Emacs Lisp. It defines
LFD to evaluate the sexp before point and insert its value in
the buffer. *Note Lisp Interaction::.

Lisp mode
The mode for editing source files of programs that run in Lisps
other than Emacs Lisp. This mode defines `C-M-x' to send the
current defun to an inferior Lisp process. *Note External Lisp::.

Inferior Lisp mode
The mode for an interactive session with an inferior Lisp process.
This mode combines the special features of Lisp mode and Shell
mode (*note Shell Mode::.).

Scheme mode
Like Lisp mode but for Scheme programs.

Inferior Scheme mode
The mode for an interactive session with an inferior Scheme
process.

File: emacs, Node: Lisp Libraries, Next: Lisp Eval, Prev: Lisp Modes, Up: Running

Libraries of Lisp Code for Emacs
================================

Lisp code for Emacs editing commands is stored in files whose names
conventionally end in `.el'. This ending tells Emacs to edit them in
Emacs-Lisp mode (*note Lisp Modes::.).

* Menu:

* Loading:: Loading libraries of Lisp code into Emacs for use.
* Compiling Libraries:: Compiling a library makes it load and run faster.
* Mocklisp:: Converting Mocklisp to Lisp so GNU Emacs can run it.

File: emacs, Node: Loading, Next: Compiling Libraries, Prev: Lisp Libraries, Up: Lisp Libraries

Loading Libraries
-----------------

To execute a file of Emacs Lisp, use `M-x load-file'. This command
reads a file name using the minibuffer and then executes the contents
of that file as Lisp code. It is not necessary to visit the file
first; in any case, this command reads the file as found on disk, not
text in an Emacs buffer.

Once a file of Lisp code is installed in the Emacs Lisp library
directories, users can load it using `M-x load-library'. Programs
can load it by calling `load-library', or with `load', a more
primitive function that is similar but accepts some additional
arguments.

`M-x load-library' differs from `M-x load-file' in that it searches a
sequence of directories and tries three file names in each directory.
The three names are, first, the specified name with `.elc' appended;
second, with `.el' appended; third, the specified name alone. A
`.elc' file would be the result of compiling the Lisp file into byte
code; it is loaded if possible in preference to the Lisp file itself
because the compiled file will load and run faster.

Because the argument to `load-library' is usually not in itself a
valid file name, file name completion is not available. Indeed, when
using this command, you usually do not know exactly what file name
will be used.

The sequence of directories searched by `M-x load-library' is
specified by the variable `load-path', a list of strings that are
directory names. The default value of the list contains the
directory where the Lisp code for Emacs itself is stored. If you
have libraries of your own, put them in a single directory and add
that directory to `load-path'. `nil' in this list stands for the
current default directory, but it is probably not a good idea to put
`nil' in the list. If you find yourself wishing that `nil' were in
the list, most likely what you really want to do is use `M-x
load-file' this once.

Often you do not have to give any command to load a library, because
the commands defined in the library are set up to "autoload" that
library. Running any of those commands causes `load' to be called to
load the library; this replaces the autoload definitions with the
real ones from the library.

If autoloading a file does not finish, either because of an error or
because of a `C-g' quit, all function definitions made by the file
are undone automatically. So are any calls to `provide'. As a
consequence, if you use one of the autoloadable commands again, the
entire file will be loaded a second time. This prevents problems
where the command is no longer autoloading but it works wrong because
not all the file was loaded. Function definitions are undone only
for autoloading; explicit calls to `load' do not undo anything if
loading is not completed.

File: emacs, Node: Compiling Libraries, Next: Mocklisp, Prev: Loading, Up: Lisp Libraries

Compiling Libraries
-------------------

Emacs Lisp code can be compiled into byte-code which loads faster,
takes up less space when loaded, and executes faster.

The way to make a byte-code compiled file from an Emacs-Lisp source
file is with `M-x byte-compile-file'. The default argument for this
function is the file visited in the current buffer. It reads the
specified file, compiles it into byte code, and writes an output file
whose name is made by appending `c' to the input file name. Thus,
the file `rmail.el' would be compiled into `rmail.elc'.

To recompile the changed Lisp files in a directory, use `M-x
byte-recompile-directory'. Specify just the directory name as an
argument. Each `.el' file that has been byte-compiled before is
byte-compiled again if it has changed since the previous compilation.
A numeric argument to this command tells it to offer to compile each
`.el' file that has not already been compiled. You must answer `y'
or `n' to each offer.

Emacs can be invoked noninteractively from the shell to do byte
compilation with the aid of the function `batch-byte-compile'. In
this case, the files to be compiled are specified with command-line
arguments. Use a shell command of the form

emacs -batch -f batch-byte-compile FILES...

Directory names may also be given as arguments;
`byte-recompile-directory' is invoked (in effect) on each such
directory. `batch-byte-compile' uses all the remaining command-line
arguments as file or directory names, then kills the Emacs process.

`M-x disassemble' explains the result of byte compilation. Its
argument is a function name. It displays the byte-compiled code in a
help window in symbolic form, one instruction per line. If the
instruction refers to a variable or constant, that is shown too.

File: emacs, Node: Mocklisp, Prev: Compiling Libraries, Up: Lisp Libraries

Converting Mocklisp to Lisp
---------------------------

GNU Emacs can run Mocklisp files by converting them to Emacs Lisp
first. To convert a Mocklisp file, visit it and then type `M-x
convert-mocklisp-buffer'. Then save the resulting buffer of Lisp
file in a file whose name ends in `.el' and use the new file as a
Lisp library.

It does not currently work to byte-compile converted Mocklisp code.
This is because converted Mocklisp code uses some special Lisp
features to deal with Mocklisp's incompatible ideas of how arguments
are evaluated and which values signify "true" or "false".

File: emacs, Node: Lisp Eval, Next: Lisp Debug, Prev: Lisp Libraries, Up: Running

Evaluating Emacs-Lisp Expressions
=================================

Lisp programs intended to be run in Emacs should be edited in
Emacs-Lisp mode; this will happen automatically for file names ending
in `.el'. By contrast, Lisp mode itself is used for editing Lisp
programs intended for other Lisp systems. Emacs-Lisp mode can be
selected with the command `M-x emacs-lisp-mode'.

For testing of Lisp programs to run in Emacs, it is useful to be able
to evaluate part of the program as it is found in the Emacs buffer.
For example, after changing the text of a Lisp function definition,
evaluating the definition installs the change for future calls to the
function. Evaluation of Lisp expressions is also useful in any kind
of editing task for invoking noninteractive functions (functions that
are not commands).

`M-ESC'
Read a Lisp expression in the minibuffer, evaluate it, and print
the value in the minibuffer (`eval-expression').

`C-x C-e'
Evaluate the Lisp expression before point, and print the value
in the minibuffer (`eval-last-sexp').

`C-M-x'
Evaluate the defun containing or after point, and print the
value in the minibuffer (`eval-defun').

`M-x eval-region'
Evaluate all the Lisp expressions in the region.

`M-x eval-current-buffer'
Evaluate all the Lisp expressions in the buffer.

`M-ESC' (`eval-expression') is the most basic command for evaluating
a Lisp expression interactively. It reads the expression using the
minibuffer, so you can execute any expression on a buffer regardless
of what the buffer contains. When the expression is evaluated, the
current buffer is once again the buffer that was current when `M-ESC'
was typed.

`M-ESC' can easily confuse users who do not understand it, especially
on keyboards with autorepeat where it can result from holding down
the ESC key for too long. Therefore, `eval-expression' is normally a
disabled command. Attempting to use this command asks for
confirmation and gives you the option of enabling it; once you enable
the command, confirmation will no longer be required for it. *Note
Disabling::.

In Emacs-Lisp mode, the key `C-M-x' is bound to the function
`eval-defun', which parses the defun containing or following point as
a Lisp expression and evaluates it. The value is printed in the echo
area. This command is convenient for installing in the Lisp
environment changes that you have just made in the text of a function
definition.

The command `C-x C-e' (`eval-last-sexp') performs a similar job but
is available in all major modes, not just Emacs-Lisp mode. It finds
the sexp before point, reads it as a Lisp expression, evaluates it,
and prints the value in the echo area. It is sometimes useful to
type in an expression and then, with point still after it, type `C-x
C-e'.

If `C-M-x' or `C-x C-e' is given a numeric argument, it prints the
value by insertion into the current buffer at point, rather than in
the echo area. The argument value does not matter.

The most general command for evaluating Lisp expressions from a
buffer is `eval-region'. `M-x eval-region' parses the text of the
region as one or more Lisp expressions, evaluating them one by one.
`M-x eval-current-buffer' is similar but evaluates the entire buffer.
This is a reasonable way to install the contents of a file of Lisp
code that you are just ready to test. After finding and fixing a
bug, use `C-M-x' on each function that you change, to keep the Lisp
world in step with the source file.

File: emacs, Node: Lisp Debug, Next: Lisp Interaction, Prev: Lisp Eval, Up: Running

The Emacs-Lisp Debugger
=======================

GNU Emacs contains a debugger for Lisp programs executing inside it.
This debugger is normally not used; many commands frequently get Lisp
errors when invoked in inappropriate contexts (such as `C-f' at the
end of the buffer) and it would be very unpleasant for that to enter
a special debugging mode. When you want to make Lisp errors invoke
the debugger, you must set the variable `debug-on-error' to
non-`nil'. Quitting with `C-g' is not considered an error, and
`debug-on-error' has no effect on the handling of `C-g'. However, if
you set `debug-on-quit' non-`nil', `C-g' will invoke the debugger.
This can be useful for debugging an infinite loop; type `C-g' once
the loop has had time to reach its steady state. `debug-on-quit' has
no effect on errors.

You can also cause the debugger to be entered when a specified
function is called, or at a particular place in Lisp code. Use `M-x
debug-on-entry' with argument FUN-NAME to cause function FUN-NAME to
enter the debugger as soon as it is called. Use `M-x
cancel-debug-on-entry' to make the function stop entering the
debugger when called. (Redefining the function also does this.) To
enter the debugger from some other place in Lisp code, you must
insert the expression `(debug)' there and install the changed code
with `C-M-x'. *Note Lisp Eval::.

When the debugger is entered, it displays the previously selected
buffer in one window and a buffer named `*Backtrace*' in another
window. The backtrace buffer contains one line for each level of
Lisp function execution currently going on. At the beginning of this
buffer is a message describing the reason that the debugger was
invoked (such as, what error message if it was invoked due to an
error).

The backtrace buffer is read-only, and is in a special major mode,
Backtrace mode, in which letters are defined as debugger commands.
The usual Emacs editing commands are available; you can switch
windows to examine the buffer that was being edited at the time of
the error, and you can also switch buffers, visit files, and do any
other sort of editing. However, the debugger is a recursive editing
level (*note Recursive Edit::.) and it is wise to go back to the
backtrace buffer and exit the debugger officially when you don't want
to use it any more. Exiting the debugger kills the backtrace buffer.

The contents of the backtrace buffer show you the functions that are
executing and the arguments that were given to them. It has the
additional purpose of allowing you to specify a stack frame by moving
point to the line describing that frame. The frame whose line point
is on is considered the "current frame". Some of the debugger
commands operate on the current frame. Debugger commands are mainly
used for stepping through code an expression at a time. Here is a
list of them.

`c'
Exit the debugger and continue execution. In most cases,
execution of the program continues as if the debugger had never
been entered (aside from the effect of any variables or data
structures you may have changed while inside the debugger).
This includes entry to the debugger due to function entry or
exit, explicit invocation, quitting or certain errors. Most
errors cannot be continued; trying to continue one of them
causes the same error to occur again.

`d'
Continue execution, but enter the debugger the next time a Lisp
function is called. This allows you to step through the
subexpressions of an expression, seeing what values the
subexpressions compute and what else they do.

The stack frame made for the function call which enters the
debugger in this way will be flagged automatically for the
debugger to be called when the frame is exited. You can use the
`u' command to cancel this flag.

`b'
Set up to enter the debugger when the current frame is exited.
Frames that will invoke the debugger on exit are flagged with
stars.

`u'
Don't enter the debugger when the current frame is exited. This
cancels a `b' command on that frame.

`e'
Read a Lisp expression in the minibuffer, evaluate it, and print
the value in the echo area. This is the same as the command
`M-ESC', except that `e' is not normally disabled like `M-ESC'.

`q'
Terminate the program being debugged; return to top-level Emacs
command execution.

If the debugger was entered due to a `C-g' but you really want
to quit, not to debug, use the `q' command.

`r'
Return a value from the debugger. The value is computed by
reading an expression with the minibuffer and evaluating it.

The value returned by the debugger makes a difference when the
debugger was invoked due to exit from a Lisp call frame (as
requested with `b'); then the value specified in the `r' command
is used as the value of that frame.

The debugger's return value also matters with many errors. For
example, `wrong-type-argument' errors will use the debugger's
return value instead of the invalid argument; `no-catch' errors
will use the debugger value as a throw tag instead of the tag
that was not found. If an error was signaled by calling the
Lisp function `signal', the debugger's return value is returned
as the value of `signal'.