How to run multiple commands synchronously from one subprocess.Popen command?

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If you want to execute many commands one after the other in the same session/shell, you must start a shell and feed it with all the commands, one at a time followed by a new line, and close the pipe at the end. It makes sense if some commands are not true processes but shell commands that could for example change the shell environment.

Example using Python 2.7 under Windows:

encoding = 'latin1'
p = subprocess.Popen('cmd.exe', stdin=subprocess.PIPE,
             stdout=subprocess.PIPE, stderr=subprocess.PIPE)
for cmd in cmds:
    p.stdin.write(cmd + "\n")
p.stdin.close()
print p.stdout.read()

To have this code run under Linux, you would have to replace cmd.exe with /bin/bash and probably change the encoding to utf8.

For Python 3, you would have to encode the commands and probably decode their output, and to use parentheses with print.

Beware: this can only work for little output. If there was enough output to fill the pipe buffer before closing the stdin pipe, this code would deadlock. A more robust way would be to have a second thread to read the output of the commands to avoid that problem.

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