Useful xonsh Commands

Last Updated: 2024-05-04

I’ve recently started using xonsh as a Linux shell. It’s extremely powerful Python-based shell. However, as the days go one, I’m trying to figure out how to do the same things in xonsh as I have in Bash, but also trying to figure out how to use things like Python list comprehension in xonsh.

Below is a list of useful things I’ve figured out how to do along the way.

Loop Through Directory

A common thing that I tend to do in Bash is loop through directories or files in the current directory to perform some tasks on them. For example (in Bash):

for i in */
do
  cd $i
  git pull origin main
  cd ../
done

The same can be done from xonsh by using the path string, p and globbing, g:

for i in pg`*`:
    cd @(i)
    git pull origin main
    cd ../

Or if you need to ensure that i is a directory, you can add additional logic:

for i in pg`*`:
    if i.is_dir():
        cd @(i)
        git pull origin main
        cd ../

Loop through command output

Another common task is to run a command and loop through the output of it to do something else. For example (I know this can be done from find), if I want to find all requirements.txt files in the current directory and run pip3 to install them, you can use captured subproccess with $() and split():

for i in $(find . -name requirements.txt).split():
    pip3 install -r @(i)

List Comprehension

Python List Comprehension is a powerful tool, and figuring out how to do it in xonsh is a bit tricky, but below is the easiest way I’ve figured out how to do it.

Example:

> for i in ['hello', 'world']:
>     echo @(i)
>
hello
world

Can be written as:

> [$[echo @(i)] for i in ['hello', 'world']]
hello
world
[None, None]

The only downside with this is that after the commands are written, an array with None is printed. This is because of how uncaptured subprocesses are handled in xonsh. To get around this, you can just assign the list comprehension to a variable.

> x = [$[echo @(i)] for i in ['hello', 'world']]
hello
world

If you want to loop through the output of a command though, use the following:

> [$[pip3 install -r @(i)] for i in $(find . -name requirements.txt).split()]