Using && In Subprocess.popen For Command Chaining?

I'm using subprocess.Popen with Python, and I haven't come across an elegant solution for joining commands (i.e. foobar&& bizbang) via Popen. I could do this: p1 = subproce

Solution 1:

&& is a shell operator, POpen does not use a shell by default.

If you want to use shell functionality use shell=True in your POpen call, but be aware that it is slightly slower/more memory intensive.

p1 = subprocess.Popen(["mmls", "WinXP.E01", "&&", "echo", "-e", "\"\n\"", "&&", "stat", "WinXP.E01"],
                      stdout=subprocess.PIPE, shell=True)

Solution 2:

How about this:

from subprocess import Popen, PIPE

def log_command_outputs(commands):
    processes = [Popen(cmd, stdout=PIPE) for cmd in commands]
    outputs = [proc.communicate()[0].split() for proc in processes]
    for output in outputs:
        for line in output:
            script_log.write(line)
        script_long.write("\n")

This starts the commands in parallel, which might make it a little faster than doing them one by one (but probably not by a large margin). Since the communicate calls are sequential though, any command that has a large output (more than a pipe's buffer) will block until it's turn comes to be cleaned up.

For your example command chain, you'd call:

log_command_outputs([["mmls", "WinXP.E01"], ["stat", "WinXP.E01"]])