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(emacs)Compilation Shell

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Subshells for Compilation
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   Emacs uses a shell to run the compilation command, but specifies the
option for a noninteractive shell.  This means, in particular, that the
shell should start 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 by setting the prompt
unconditionally.  (This init file's name may be `.bashrc', `.profile',
`.cshrc', `.shrc', or various other things, depending on the shell you
use.)  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 = ...

And here's how to do it in bash:

     if [ "${PS1+set}" = set ]
     then PS1=...
     fi

   There may well be other things that your shell's init file ought to
do only for an interactive shell.  You can use the same method to
conditionalize them.

   The MS-DOS "operating system" does not support asynchronous
subprocesses; to work around this lack, `M-x compile' runs the
compilation command synchronously on MS-DOS.  As a consequence, you must
wait until the command finishes before you can do anything else in
Emacs.  Note: MS-DOS.