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Ubuntu – Newline character written to file with echo works in shell, but literal in Python 3

I’m on a Ubuntu 20.04 system, and I’m using Python 3.8 to write a script that does multiple things using configurable lines of bash, but one of them is that it creates desktop shortcuts.

This single-line command creates a desktop shortcut, and works flawlessly when I execute it directly in my terminal:

echo "[Desktop Entry]"$'n'"Type=Application"$'n'"Name[en_US]=Documents"$'n'"Exec=pcmanfm ~/Documents"$'n'"Icon=system-file-manager" > ~/Desktop/1;

However, when I execute it in Python, like so:

foobar.py

rl = """echo "[Desktop Entry]"$'n'"Type=Application"$'n'"Name[en_US]=Documents"$'n'"Exec=pcmanfm ~/Documents"$'n'"Icon=system-file-manager" > ~/Desktop/1;"""
subprocess.run(rl, shell=True)

…instead of creating a desktop shortcut with the proper name, icon, and action, it creates an empty file that contains the following text:

0.txt:

[Desktop Entry]$nType=Application$nName[en_US]=Sign Out$nExec=/home/agent/QaSC/login/login.bin$nIcon=system-switch-user

Is there any particular reason why Python would be handling the newline characters differently than the bash shell does, and if so, how can I resolve this problem?

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2

Answers


  1. 0

    $'...' is a bash extension, but the default shell used when shell=True is specified is sh. Use the executable option to specify an alternate shell.

    subprocess.run(rl, shell=True, executable='/bin/bash')
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  2. 0

    Since the argument to echo has quotes, it could contain literal newlines at the command line, and therefore also in the Python process. I see no reason to use the Bash extension $'n' syntax.

    $ echo "foo
> bar"
foo
bar
$ python
Python 3.8.10 (default, Mar 15 2022, 12:22:08) 
[GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import subprocess
>>> subprocess.run('echo "foonbar"', shell=True)
foo
bar
CompletedProcess(args='echo "foonbar"', returncode=0)
>>>

    (It’s also unclear why the Python code doesn’t just write a file in the normal way, but I assume the command in the OP is essentially a placeholder.)

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