Python3 Run Alias Bash Commands

Question

I have the following code that works great to run the ls command. I have a bash alias that I use alias ll='ls -alFGh' is it possible to get python to run the bash command without python loading my bash_alias file, parsing, and then actually running the full command?

import subprocess

command = "ls"  # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=None, shell=True)

#Launch the shell command:
output = process.communicate()

print (output[0])

Trying with command = "ll" the output I get is:

/bin/sh: ll: command not found
b''

Possible duplicate: stackoverflow.com/questions/12060863/… — Tanner
– Tanner, Commented Mar 9, 2016 at 19:42
I don't want to be obnoxious, but why are you using subprocess to list files? Wouldn't import os os.listdir() achieve what you want? — DaveBensonPhillips
– DaveBensonPhillips, Commented Mar 9, 2016 at 19:44
Please note alias' are a shell thing, not a bash thing, so, your system has no knowledge of the alias. You can have the command execute through a shell, but that will still result in your alias file being parsed (when the shell loads it will parse it) — Tanner
– Tanner, Commented Mar 9, 2016 at 19:44
My actual command is piping commands into a docker container, this was just an example to break the problem down — ClickThisNick
– ClickThisNick, Commented Mar 9, 2016 at 19:44
Also, this doesn't answer your question, but you can of course do subprocess.Popen(['ls', '-alFGh'], stdout=subprocess.PIPE, stderr=None) instead (especially given shell=True is generally disuaded). — DaveBensonPhillips
– DaveBensonPhillips, Commented Mar 9, 2016 at 19:47

cdarke · Accepted Answer · 2016-03-09 20:06:17Z

1

You cannot. When you run a python process it has no knowledge of a shell alias. There are simple ways of passing text from parent to child process (other than IPC), the command-line and through environment (i.e. exported) variables. Bash does not support exporting aliases.

From the man bash pages: For almost every purpose, aliases are superseded by shell functions.

Bash does support exporting functions, so I suggest you make your alias a simple function instead. That way it is exported from shell to python to shell. For example:

In the shell:

ll() { ls -l; }
export -f ll

In python:

import subprocess

command = "ll"  # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=None, shell=True)

output = process.communicate()

print(output[0].decode())    # Required if using Python 3

Since you are using the print() function I have assumed you are using python 3. In which case you need the .decode(), since a bytes object is returned.

With a bit of hackery it is possible to create and export shell functions from python as well.

answered Mar 9, 2016 at 20:06

cdarke

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1 Comment

ClickThisNick Over a year ago

THANK YOU! This is very very helpful

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