V.4 Subshells for Compilation

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. See section AH. Emacs and MS-DOS.