3 ms·

Thanks for pointing me to nim, it looks promising. I‘ll try to use https://nim-lang.org/docs/osproc.html https://nim-lang.org/docs/osproc.html to pipe programs.

by lysium 3y ago

Thanks for pointing me to nim, it looks promising. I‘ll try to use https://nim-lang.org/docs/osproc.html https://nim-lang.org/docs/osproc.html to pipe programs. My use case is approx. like this: I can get 80% what I want with ls … | sed … | grep -v … but then it gets complicated in the script and I’d like to replace the sed or grep part with some program.

cb321 3y ago
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 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 )
- lysium 3y ago
  Thank you! Popen looks like what I was looking for!
  - cb321 3y ago
    Sure. No problem. While it may not be in any ANSI/ISO spec for C, even Windows has popen these days. There are also some tiny Nim popenr/popenw wrappers in https://github.com/c-blake/cligen/blob/master/cligen/osUt.nim https://github.com/c-blake/cligen/blob/master/cligen/osUt.ni... covering the Windows case. Depending upon how balanced work is on either side of the pipe, you usually can even get parallel speed-up on multicore with almost no work. For example, there is no need to use quote-escaped CSV parsing libraries when you just read from a popen()d translator program producing an easier format: https://github.com/c-blake/nio/blob/main/utils/c2tsv.nim https://github.com/c-blake/nio/blob/main/utils/c2tsv.nim

by lysium 3y ago

cb321 3y ago

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 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 )

lysium 3y ago
Thank you! Popen looks like what I was looking for!
- cb321 3y ago
  Sure. No problem. While it may not be in any ANSI/ISO spec for C, even Windows has popen these days. There are also some tiny Nim popenr/popenw wrappers in https://github.com/c-blake/cligen/blob/master/cligen/osUt.nim https://github.com/c-blake/cligen/blob/master/cligen/osUt.ni... covering the Windows case. Depending upon how balanced work is on either side of the pipe, you usually can even get parallel speed-up on multicore with almost no work. For example, there is no need to use quote-escaped CSV parsing libraries when you just read from a popen()d translator program producing an easier format: https://github.com/c-blake/nio/blob/main/utils/c2tsv.nim https://github.com/c-blake/nio/blob/main/utils/c2tsv.nim