Mirror of forum.nim-lang.org

5025 :: Passing a Variable as Part of Args to execProcess

• madra (orginal) [2019-07-17T16:58:59+02:00] view original

  Another day, another bit of tinkering with some of my old Python scripts to try and get my head round Nim.

  This is an old script I had which takes a list of [IMHO] junk processes and kills them on my OSX laptop. [For the purposes of testing I'm just using Finder and Dock as placeholders, as they'll relaunch automatically after killing, which speeds up testing]

  Assuming execProcess is the way to go, I've come up with:

  
  #import
  import osproc
  
  #processes to kill
  var processes = ["Finder","Dock"]
  for process in processes:
    execProcess("pkill", args=[" -9", process])
  Run

  but, when I run that I get:

  
  Error: expression 'execProcess("pkill", [" -9", process], nil,
              {poStdErrToStdOut, poUsePath, poEvalCommand})' is of type 'TaintedString' and has to be discarded
  Run

  "TaintedString" is a new one on me. But I'm assuming it's the usual newbie error when trying out a strongly typed language and I'm somehow mixing types in the command I'm passing to execProcess. So I tried with:

  
  execProcess("pkill", args=[" -9", $process])
  Run

  instead. But still got the same error.

  The example in the docs has the args to the command 'hard-wired':

  
  let outp = execProcess("nim", args=["c", "-r", "mytestfile.nim"], options={poUsePath})
  let outp_shell = execProcess("nim c -r mytestfile.nim")
  Run

  So, how do I pass args in as a variable?

---

• leorize (orginal) [2019-07-17T17:28:44+02:00] view original

  You're missing the important part in that example:

  let outp =
  Run

  The way you're doing it is correct, but execProcess returns a TaintedString (doc), so you'd have to capture it or explicitly discard the result with discard like this:

  # default options contains poEvalCommand, which will ignore args, so we specify our own set
  discard execProcess("pkill", args=[" -9", process], options = {poStdErrToStdOut, poUsePath})
  Run

  Unlike most languages, Nim does not allow you to drop a function return value implicitly.

---

• madra (orginal) [2019-07-17T17:59:42+02:00] view original

  Aha. That worked a treat

  I'd thought the TaintedString error was telling me I was creating a "tainted string" when building the command. And the reason I'd omitted the let outp = was that it looked like that was assigning the result of the command to a varible so it could be used later on –and I just wanted it to run & exit.

  Thanks for your help.

---