Python module to shellquote/unshellquote?

You should never have to shell quote. The correct way to do a command is to not do shell quoting and instead use subprocess.call or subprocess.Popen, and pass a list of unquoted arguments. This is immune to shell expansion.

i.e.

subprocess.Popen(['echo', '"', '$foo'], shell=False)

If you want to unquote shell quoted data, you can use shlex.shlex like this:

list(shlex.shlex("hello stack 'overflow'''s' quite cool"))

Looks like

try:  # py3
    from shlex import quote
except ImportError:  # py2
    from pipes import quote

quote("hello stack overflow's quite cool")
>>> '"hello stack overflow's quite cool"'

gets me far enough.

I’m pretty sure that pipes.quote is broken, and should not be used, because it does not handle zero-length arguments correctly:

>>> from pipes import quote
>>> args = ['arg1', '', 'arg3']
>>> print 'mycommand %s' % (' '.join(quote(arg) for arg in args))
mycommand arg1  arg3

I believe the result should be something like

mycommand arg1 '' arg3

The standard library module subprocess has the list2cmdline function which does this, albeit according to Microsoft rules so I am not sure how reliable it works in Unix-like environments for more complicated command lines.

To unquote, try shlex.split()

For shell quoting, this works: I’ve rigorously tested it on Posix. [I’m assuming that the list2cmdline function supplied by Python works as advertised on Windows]

# shell.py
import os
if os.name == 'nt':
    from subprocess import list2cmdline

    def quote(arg):
        return list2cmdline([arg])[0]
else:
    import re
    _quote_pos = re.compile('(?=[^-0-9a-zA-Z_./n])')

    def quote(arg):
        r"""
        >>> quote('t')
        '\t'
        >>> quote('foo bar')
        'foo\ bar'
        """
        # This is the logic emacs uses
        if arg:
            return _quote_pos.sub('\\', arg).replace('n',"'n'")
        else:
            return "''"

    def list2cmdline(args):
        return ' '.join([ quote(a) for a in args ])

The tests are here, if anyone cares.

The quotefunction is available for quite some time (Python 2.7?) — the major drawback is it moved from pipe module to shlex between 3.2 and 3.3.

You have to be prepared to handle both cases while importing that function:

try:
    from shlex import quote
except ImportError:
    from pipes import quote