22.1 Running "make", or Compilers Generally
Emacs can run compilers for non-interactive languages like 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 to the line where the error
Run a compiler asynchronously under Emacs, with error messages to
Run `grep' asynchronously under Emacs, with matching lines listed
in the buffer named `*compilation*'.
Kill the process made by the `M-x compile' command.
Kill the running compilation or `grep' subprocess.
Visit the next compiler error message or `grep' match.
To run `make' or another compiler, type `M-x compile'. This command
reads a shell command line using the minibuffer, then executes the
specified command line in an inferior shell with output going to the
buffer named `*compilation*'. By default, the current buffer's default
directory is used as the working directory for the execution of the
command; therefore, the makefile comes from this directory.
When the shell command line is read, the minibuffer appears
containing a default command line (the command you used the last time
you typed `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).
When you start a compilation, the buffer `*compilation*' is
displayed in another window but not selected. Its mode line displays
the word `run' or `exit' in the parentheses to tell you whether
compilation is finished. You do not have to keep this buffer visible;
compilation continues in any case.
To kill the compilation process, type `M-x kill-compilation'. 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 occur at any time. Starting a new
compilation prompts for confirmation before actually killing a
compilation that is running.
To parse the compiler error messages, type `C-x `' (`next-error').
The character following `C-x' is the grave accent, not the single
quote. The 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 you use `C-x `' after the start of a compilation, it
parses all the error messages, visits all the files that have error
messages, and creates markers pointing at the lines the error messages
refer to. It then 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 compiler errors while compilation is still going on.
If no additional 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 again, then displays 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 to
`grep': a `grep'-style regexp (usually in single quotes to quote the
shell's special characters) followed by filenames, which may use
wildcard characters. The output from `grep' goes in the
`*compilation*' buffer. You can use `C-x `' to find the lines that
match as if they were compilation errors.
Note: a shell is used to run the compile command, but the shell is
not run in interactive mode. In particular, this means 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 initialization file (`.cshrc' or `.shrc'
or ...) by setting the prompt unconditionally. The shell
initialization file should set the prompt only if there already is a
prompt. Here's how to do it in `csh':
if ($?prompt) set prompt = ...
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