This sounds like a job for what standard C calls "popen". You can do

    import posix; for line in popen("ls", "r").lines: echo line

in Nim, though you obviously need to replace `echo line` with other desired processing and learn how to do that.

You might also want to consider `rp` which is a program generator-compiler-runner along the lines of `awk` but with all the code just Nim snippets interpolated into a program template: https://github.com/c-blake/bu/blob/main/doc/rp.md . E.g.:

    $ ls -l | rp -pimport\ stats -bvar\ r:RunningStat -wnf\>4 r.push\ 4.f -eecho\ r
    RunningStat(
      number of probes: 26
      max: 31303.0
      min: 23.0
      sum: 84738.0
      mean: 3259.153846153846
      std deviation: 6393.116633069013
    )