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I would like to execute multiple commands in a row:

ie (just to illustrate my need):

cmd (the shell)


cd dir



and read the result of the ls.

Any idea with subprocess module ?


cd dir and ls are just an example. I need to run complex commands (following a particular order, without any pipelining). In fact, i would like one subprocess shell and the ability to launch many commands on it.

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maybe you should write a shell script instead of a python script –  hop Dec 11 '08 at 14:10
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4 Answers

up vote 11 down vote accepted

There is an easy way to execute a sequence of commands.

Use the following in subprocess.Popen

"command1; command2; command3"

Or, if you're stuck with windows, you have several choices.

  • Create a temporary ".BAT" file, and provide this to subprocess.Popen

  • Create a sequence of commands with "\n" separators in a single long string.

Use """s, like this.


Or, if you must do things piecemeal, you have to do something like this.

class Command( object ):
    def __init__( self, text ):
        self.text = text
    def execute( self ):
        self.proc= subprocess.Popen( ... self.text ... )

class CommandSequence( Command ):
    def __init__( self, *steps ):
        self.steps = steps
    def execute( self ):
        for s in self.steps:

That will allow you to build a sequence of commands.

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subprocess.Popen("ls") works. However, subprocess.Popen("ls; ls") fails for me. Error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib64/python2.6/subprocess.py", line 639, in __init__ errread, errwrite) File "/usr/lib64/python2.6/subprocess.py", line 1228, in _execute_child raise child_exception OSError: [Errno 2] No such file or directory –  thoughtadvances Sep 18 '12 at 15:51
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To do that, you would have to:

  • supply the shell=True argument in the subprocess.Popen call, and
  • separate the commands with:
    • ; if running under a *nix shell (bash, ash, sh, ksh, csh, tcsh, zsh etc)
    • & if running under the cmd.exe of Windows
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Or for windows, can use && so that a command that errors out will prevent execution of the commands after it. –  twasbrillig Jan 26 at 20:45
@twasbrillig Interesting; I didn't know that cmd.exe shared this command separator with Unix shells. I should update my knowledge. Thanks! –  tzot Jan 27 at 7:47
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Yes, the subprocess.Popen() function supports a cwd keyword argument, with which you can set the directory it runs the process in.

I guess the first step, the shell, is not needed, if all you want is to run ls, there's no need to run it through a shell.

Of course, you could also just pass the desired directory as an argument to ls.

Update: it might be worth noting that for typical shells, cd is implemented in the shell itself, it is not an external command on disk. This is because it needs to change the process' current directory, which must be done from within the process. Since commands run as child processed, spawned by the shell, they cannot do this.

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Finding 'bar' in every file whose name contains 'foo':

from subprocess import Popen, PIPE
find_process = Popen(['find', '-iname', '*foo*'], stdout=PIPE)
grep_process = Popen(['xargs', 'grep', 'bar'], stdin=find_process.stdout, stdout=PIPE)
out, err = grep_process.communicate()

'out' and 'err' are string objects containing the standard output and, eventually, the error output.

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