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I have

(shell-command-to-string "ls")

which works just fine but when I put it in a function it breaks as

(defun testing ()
  (shell-command-to-string "ls")
)

outputs nil. I am new to elisp so I am clearly missing something. Can someone point me in the right direction?

5
  • I cannot reproduce this. How are you calling the function testing? Dec 15, 2021 at 19:10
  • Just testing() and running C-x C-e on the function itself then the calling of the function.
    – Hercislife
    Dec 15, 2021 at 19:23
  • To call the function, you have to write (testing) - if you do C-x C-e after that, does it work?
    – NickD
    Dec 15, 2021 at 19:40
  • @NickD Thanks for that! Everything seems to work now. Want to make an answer so I can accept it?
    – Hercislife
    Dec 15, 2021 at 19:59
  • You should probably add the way that you tried to call the function to your question. Without that detail, the question is incomplete.
    – NickD
    Dec 15, 2021 at 20:15

1 Answer 1

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In Lisp, a function call is denoted like this: (func arg1 arg2 ...). IOW, the first element of the list is the function and subsequent elements are the (evaluated) arguments. Contrast this with most other languages where a function call is denoted like this: func(arg1, arg2, ...).

So you define the function like this:

(defun testing ()
  (shell-command-to-string "ls")
)

Doing C-x C-e after the closing paren evaluates the defun and adds the definition of the function to the system. Then to call the function you say:

(testing)

This calls the function testing with no arguments.

You should probably read the "Introduction to Programming in Elisp" which can be found here.

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