Call a bash function within a python script

Question

I have a python script (e.g. test.py) and a commands.txt file which contains a custom bash function (e.g. my_func) along with its parameters, e.g.

my_func arg1 arv2; my_func arg3 arg4; my_func arg5 arg6;

This function is included in the ~/.bash_profile. What I have tried to do is:

subprocess.call(['.', path/to/commands.txt], shell=True)

I know this is not the best case, in terms of setting the shell argument into True, but I cannot seem to implement it even in this way. What I get when I run test.py is: my_func: command not found

Have you exported the function from your .bash_profile? export -f my_func. If you don't do that then it is only visible to the interactive session you define it in, i.e. it does not get passed to child processes. — cdarke
– cdarke, Commented Nov 8, 2017 at 16:43
@cdarke No, I haven't done that. Also, my_func uses other bash functions in its definition. Does this affect anything? — thanasissdr
– thanasissdr, Commented Nov 8, 2017 at 16:55
subprocess.call(['for arg; do . "$arg"; done', '_', os.path.expanduser('~/.bashrc'), '/path/to/commands.txt'], shell=True) will work, if and only if your scripts (commands.txt and .bashrc) are both compatible with /bin/sh. — Charles Duffy
– Charles Duffy, Commented Nov 8, 2017 at 17:09
@thanasissdr, ...you'll want to export both the function itself and its dependencies -- with that done, subprocess.Popen(['bash', '-c', 'funcname "$@"', '_'] + args) will be able to run it (with args being a Python list of arguments to pass to the function, ie. args=['foo', 'bar', 'baz'] to run funcname foo bar baz). Using bash instead of shell=True makes sure you get a shell that actually knows how to read those exported functions, and passing arguments out-of-band from code is a security precaution: you don't want to pass a freeform field and have someone put $(rm -rf ~) in it. — Charles Duffy
– Charles Duffy, Commented Nov 8, 2017 at 20:30
@CharlesDuffy Thank you for the comment. Would it be possible to write a simple example? — thanasissdr
– thanasissdr, Commented Nov 9, 2017 at 9:28

Aaron Bentley · Accepted Answer · 2017-11-08 16:41:41Z

2

You will need to invoke bash directly, and instruct it to process both files.

At the command-line, this is:

bash -c '. ~/.bash_profile; . commands.txt'

Wrapping it in python:

subprocess.call(['bash', '-c', '. ~/.bash_profile; . commands.txt'])

You could also source ~/.bash_profile at the top of commands.txt. Then you'd be able to run a single file.

It may make sense to extract the function to a separate file, since .bash_profile is intended to be used by login shells, not like this.

edited Nov 8, 2017 at 16:41

answered Nov 8, 2017 at 16:20

Aaron Bentley

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2 Comments

thanasissdr Over a year ago

The function is defined within the ~/.bash_profile.

Aaron Bentley Over a year ago

Updated to reflect this. When you said "I have a ... commands.txt file which contains a custom bash function (e.g. my_func)", I thought you meant that it contained the function definition.

Cédric Julien · Accepted Answer · 2017-11-08 15:54:22Z

0

If the first line of your commands.txt file had the correct shebang (for example #!/bin/bash) making your file executable (chmod +x commands.txt) will be enough :

subprocess.call("path/to/commands.txt")

answered Nov 8, 2017 at 15:54

Cédric Julien

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6 Comments

Van Peer Over a year ago

the extension txt doesn't matter?

thanasissdr Over a year ago

@CedricJulien Thanks for the answer, is it possible to make the text file executable within the python script? subprocess.call(['chmod +x', ' absolute/path/to/commands.txt'], shell=True) would work as well?

Cédric Julien Over a year ago

@VanPeer Posix systems (like Linux) doesn't care of the extension

Cédric Julien Over a year ago

@thanasissdr yes, it could be possible

thanasissdr Over a year ago

@CedricJulien I tried that but still I get the same error.

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