Perl closing pipe without errors

Question

I am using Perl to execute an external program and would like to end it if it returns a specific line at runtime. The code below interrupts execution as desired, however, an error message is returned when the last line is executed (closing).

open (my $out, "-|", "usfos $memory<input-$cpu.scr");
while (<$out>) {
    if ($_ =~ /MIN   STEP  LENGTH/) {
        last;
    }
}
close $out;

This is part of the error being printed (the external program also returns error messages):

...forrtl: The pipe is being closed.
forrtl: severe (38): error during write, unit 6, file CONOUT$

So, I think this is because Perl is trying to write a closed descriptor. How can I avoid printing?

Answer 1

You do not shut down an external program when close $out, you close it STDOUT.

, . open pid, . , .

use Scalar::Util qw(openhandle); # to check whether the handle is open

my $pid = open (my $out, "-|", "usfos $memory<input-$cpu.scr") 
                // die "Can't fork: $!";   # / stop editor red coloring
while (<$out>) {
    if (/MIN   STEP  LENGTH/) {
        kill "TERM", $pid;   # or whatever is appropriate; add checks
        close $out;          # no check: no process any more so returns false
        last;
    }
}
# Close it -- if it is still open. 
if (openhandle($out)) {          
    close $out or warn "Error closing pipe: $!";
}

open opentut, close.

Fortran (STDOUT), , : (last) STDOUT, .

. . , close, $? . SIGPIPE . close

, close false, . , , $! 0. , - , - $? $ {^ CHILD_ERROR_NATIVE}.
...
, , SIGPIPE. , .

---

, , STDOUT , ( ). , , SIGPIPE , , , . ( ?) , , close($out) , , $out .

close , ( kill ). , , , , . Scalar::Util, - fileno. , , kill , .

---

Windows , . , , Win32::Process::Kill, kill. ( . Windows, , .) ,

• Win32::Process::List

  use Win32::Process::Kill;
  use Win32::Process::List;
  my $pobj = Win32::Process::List->new(); 
  my %proc = $pobj->GetProcesses(); 
  my $exitcode;
  foreach my $pid (sort { $a <=> $b } keys %proc) {
      my $name = $proc{$pid};
      if ($name =~ /usfos\.exe/) {
          Win32::Process::KillProcess($pid, \$exitcode);
          # kill 21, $pid;
          last;
      }
   }
  

• Win32::Process::Info. .

  use Win32::Process::Info;
  Win32::Process::Info->Set(variant=>'WMI');   # SEE DOCS about WMI
  my $pobj = Win32::Process::Info->new();
  foreach my $pid ($pobj->ListPids) {
      my ($info) = $pobj->GetProcInfo($pid);
      if ($info->{CommandLine} =~ /^usfso/) {  # command-line, not name
          my $proc = $info->{ProcessId};
          kill 2, $proc; 
          last;
      }
  }
  

  , Subprocesses([$ppid,...]), $ppid (s). , $ppid -ref $pid $ppid.

  use Win32::Process::Info;
  Win32::Process::Info->Set(variant=>'WMI');
  my $pobj = Win32::Process::Info->new();
  my %subproc = $pobj->Subprocesses([$pid]);   # pid returned by open() call
  my $rkids = $subproc{$pid};
  foreach my $kid (@$rkids) {
      print "pid: $kid\n";                     # I'd first check what is there
  }
  

• Windows TASKKILL/T TASKKILL/T

  system("TASKKILL /F /T /PID $pid");
  

.