Create your own Linux commands in Python

About this article

Python is used for various purposes these days, but it is also useful when you want to automate small tasks such as file operations!

[Let Python do the boring things]( 81% A8% E3% 81% AFPython% E3% 81% AB% E3% 82% 84% E3% 82% 89% E3% 81% 9B% E3% 82% 88% E3% 81% 86-% E2% 80 % 95% E3% 83% 8E% E3% 83% B3% E3% 83% 97% E3% 83% AD% E3% 82% B0% E3% 83% A9% E3% 83% 9E% E3% 83% BC % E3% 81% AB% E3% 82% 82% E3% 81% A7% E3% 81% 8D% E3% 82% 8B% E8% 87% AA% E5% 8B% 95% E5% 8C% 96% E5 % 87% A6% E7% 90% 86% E3% 83% 97% E3% 83% AD% E3% 82% B0% E3% 83% A9% E3% 83% 9F% E3% 83% B3% E3% 82 There is even a book called% B0-Al-Sweigart / dp / 487311778X). ↑ I'm not an affiliate (just in case)

In this article, I'll show you how to execute such Python code as if it were a command!


This time, we will follow the steps while creating a command to display the file list, `filelist```. (Something like ls``)

If you want to introduce the procedure in one word ** Give execute permission to the file "filelist" that specifies the python interpreter (`#! / usr / bin / env python```) in Shebang, and put the file in the saved directory in the PATH. Can be executed with filelist ``. ** ** It's like that.

The implementation flow is shown below.

0. Premise

It is assumed that Python is already installed and can be executed with the `` `python``` command. If you search for "python installation linux" etc., various methods will appear, so please refer to it.

1. Script creation

First, create a script to execute. Create an appropriate folder and save it in it.

  1. Create a "pycommands" directory in your home directory
mkdir ~/pycommands
  1. Move to the "pycommands" directory
cd ~/pycommands
  1. Create a file "filelist" and go to the edit screen
vi filelist
  1. Edit the file "filelist"
#!/usr/bin/env python

import os
from pathlib import PATH

#The directory where the user is currently (os.getcwd()) Get information
current_dir = PATH(os.getcwd())

# glob("*")Get a list of files in the directory where the user is currently
for file in current_dir.glob("*"):

The important thing here is the `#! / Usr / bin / env python``` on the first line. This is called ** Shebang ** and specifies what to use to interpret the contents of the file. Since Python is specified here, Python code is executed even if it is not written as `.py```. (If you specify Ruby etc. in this part, you can also execute Ruby code.)

2. Grant execution authority

The file "filelist" you just created is not a file that can be executed yet. To do this, you need to give the file ** execute permissions **.

To give execute permission to a file

chmod u+x ~/pycommands/filelist

To execute. (It is assumed that "filelist" is created under `~ / pycommands /`. If you create it in a different location, change the command accordingly.)


 In this state, the execution itself can already be performed.
 At any place


When you enter the command, a list of files should be output.

The next step will allow you to do this by simply typing filelist.

3. Pass through PATH

Then make it possible to run this command from anywhere.

In order to be able to execute a command located in a certain place from anywhere, it is necessary to set the PATH environment variable.

Roughly speaking, PATH is "a list of places to go to find an executable file with that name when you enter a ** command (likely thing) **".

lsWhen I enter the command, it goes looking for an executable file named "ls" in the path and runs the file I find. (Searching while accessing the location list defined in PATH one by one from the front.)

For the time being, to execute only this time

export PATH='$PATH:$HOME/pycommands/'

It is OK if you execute.

To be able to use it all the time

echo export PATH='$PATH:$HOME/pycommands/' >> ~/.bashrc
source ~/.bashrc

Is OK.

4. Run!

Wherever you are


If you execute, a list of files will be displayed.

If not executed

There is already a command with the same name

If a command with the same name already exists, the command with the same name as the command created in this flow already exists, so it will be searched for first in the PATH and the created command will not be executed. (Because I added a directory at the end of PATH)

Change the name or change the order of the PATH so that it will be executed first. (Not recommended)


Let's make a command to make the work convenient ^ ^

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