Ben Finney wrote:
Jean-Michel Pichavant <jeanmic...@sequans.com> writes:
Can someone explain the difference with the shell argument ? giving
for instance an example of what True will do that False won't.
The ‘shell’ argument to the ‘subprocess.Popen’ constructor specifies
whether the command-line should be invoked directly (‘shell=False’) or
indirectly through invoking a shell (‘shell=True’).
If ‘shell=False’, the command-line arguments are used as direct
arguments to the kernel's “run this program for me”.
If ‘shell=True’ the command-line arguments are themselves passed to a
new instance of the user's current shell, as a command line that *it*
should invoke on the program's behalf. This allows the command line to
be manipulated and interpolated etc., the way it would be if typed at a
new shell prompt. Then, that shell will in turn ask the kernel “run this
program for me” as it normally does after processing the arguments.
I mean, I've read the doc, and to be honest, I didn't get it. I'm
concerned because I'm using subprocess, but I guess my shell arg has
been filled a little bit random..
Use ‘shell=False’ by default (which, since that's the default for
‘subprocess.Popen’, means you can omit it entirely), and specify exactly
the command line arguments you want the kernel to execute. Only if you
know you want a shell process to be involved should you use
‘shell=True’.
Thank you Ben for the update. It's clear for me now, I've checked and I
use it with no shell arg, except at one place, but I don't think it's
intended and it happens to work anyway. I've added a small comment just
in case it fails in the future.
JM
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