blog/2025-07-21/calling-shell-commands-from-yaml/

[giscus[bot]]

blog/2025-07-21/calling-shell-commands-from-yaml/

Program in YAML — Code is Data

https://yamlscript.org/blog/2025-07-21/calling-shell-commands-from-yaml/

[zostay]

Is it possible to pass a string as the input to stdin using any of the shell functions? If so, how?

[ingydotnet]

Greetings @zostay!

Yes, you can do that.

Here's an example:

$ ys upside-down.ys 
This is file 'upside-down.ys', up side down:

================================================
      ================================================
      $(result.out:chomp)
      ================================================

      This is file '$fs-basename(FILE)', up side down:
    say: |
  when result.exit.!:

      'tac'
    sh {:in text}:
  result =:

  text =: file:read
defn main(file=FILE):

!YS-v0
================================================

$ 

See if you can figure out what the actual YS program is. 😄

Please ask more questions!!!

[ingydotnet]

Here's a more obvious example of using the :in option:

$ ys -e 'shell({:in (\\A .. \\E):text} "cat -n")'
     1	A
     2	B
     3	C
     4	D
     5	E

[ingydotnet]

@zostay Note there's a mistake in https://github.com/yaml/yamlscript/blob/v0/core/src/ys/std.clj#L838-L871
where I forgot to add calls to process-opts (which enables :in etc) to bash and bash-out, but I'll fix that soon.

If you want to give it a try, submit a PR!
bash is nice for compound shell commands like foo | bar > baz.
It just wraps the command with bash -c '...'.

Also let me know which parts of the docs would have made this clearer.
You can submit PRs for doc changes right in the web page for that doc, with the edit button.

[ingydotnet]

The docs for those is here: https://yamlscript.org/doc/ys-std/#ipc-functions

Obviously they need some updating.

[ingydotnet]

Docs updated now: https://yamlscript.org/doc/ys-std/#ipc-functions