On Wed, 21 Oct 2009 11:24:37 -0400, Tim Arnold wrote: > Hi, I'm writing a script to capture a command on the commandline and run it > on a remote server. > I guess I don't understand subprocess because the code below exec's the > user's .cshrc file even though by default shell=False in the Popen call.
Using shell=True causes Popen to explicitly invoke the command via a shell, i.e. "/bin/sh -c <command>" on Unix or "cmd /c <command>" on Windows. If you use shell=False (the default), it uses fork()+exec() or CreateProcess(). If the command which you are running ends up invoking a shell (as rsh probably does), that's nothing to do with Popen. In particular, if csh is being invoked, that isn't Popen's doing. It will use either /bin/sh on Unix or %COMSPEC% (which is typically cmd.exe) on Windows. > Since the shell is executing in the child process anyway, is the only > difference when using shell=True is that environment variables can be > expanded in the command to be executed? The difference is that the shell gets involved, so you can use environment variables, backticks, redirections, pipelines, shell-builtins etc. It also means that you need to quote or escape spaces and shell metacharacters within arguments if you want them to be treated literally. -- http://mail.python.org/mailman/listinfo/python-list
