Re: How to split stderr/stdout of a subprocess?

[akavel]

Thanks! I didn't check the Linux version yet, but the Windows one doesn't seem 
to really do what I need: specifically, if I print from a Nim file like this:
    
    
    # q_outerr.nim
    import os
    
    stdout.writeLine "some stdout"
    stderr.writeLine "some stderr"
    stderr.writeLine "some stderr2"
    sleep(milsecs = 5_000)
    stderr.writeLine "some stderr3"
    stderr.writeLine "some stderr4"
    
    
    Run

with the windows part of the "reader" file modified like this:
    
    
    # q_peek.nim
    ...
      else:
        echo "on windows"
        let prc = startProcess("q_outerr", options = {})
        var errstream = errorStream prc
        var outstream = outputStream prc
        while true:
          if errstream.atEnd:
            echo "err end"
          else:
            let edata = errstream.peekLine
            if edata != "":
              echo "stderr: ", errstream.readLine
          if outstream.atEnd:
            echo "out end"
          else:
            let odata = outstream.peekLine
            if odata != "":
              echo "stdout: ", outstream.readLine
          if errstream.atEnd and outstream.atEnd:
            echo "-break-"
            break
    ...
    
    
    Run

I'm getting a SIGSEGV:
    
    
    on windows
    Traceback (most recent call last)
    C:\prog\mana\q_peek.nim(61) q_peek
    C:\prog\mana\q_peek.nim(48) main
    C:\Users\Mateusz\.choosenim\toolchains\nim-1.0.4\lib\pure\streams.nim(979) 
peekLine
    C:\Users\Mateusz\.choosenim\toolchains\nim-1.0.4\lib\pure\streams.nim(213) 
getPosition
    SIGSEGV: Illegal storage access. (Attempt to read from nil?)
    Error: execution of an external program failed: 'C:\prog\mana\q_peek.exe '
    
    
    Run

I also tried readLine instead of peekLine, but then the sleep makes q_peek 
block until after sleep is finished. I want to be able to discern if there's 
some stderr available from a _not yet finished_ subprocess...

What do you refer to in: " _createIoCompletionPort_ apparently couldn't work"? 
couldn't where? did someone try it sometime? I think in Go they maybe managed 
to somehow make it work?

For now, at least as far as solution for Windows, it seems I'm still looking 
for help...