Re: Executing a program, displaying some status, and killing it

Check out fork and exec. Something like:

my $child = fork;
if ($child) {
  # I am in the parent...wait then kill
  for my $i in (1..10) {
    sleep 1;
    print ".";
  }
  kill -9, $child;
}
else {
  # Run the background program
  exec '/path/to/program/that/would/output/something/and/run/forever >
+ /dev/null 2>&1';
}
[download]

There is more to error checking for return values than I illustrate here. Do see the documentation for examples.

Caution: Contents may have been coded under pressure.

Comment on Re: Executing a program, displaying some status, and killing it Download Code

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Re^2: Executing a program, displaying some status, and killing it by revdiablo (Prior) on Dec 08, 2004 at 01:15 UTC
I realize you were probably doing a quick port, but there are a few things I would like to point out. You create an explicit variable with your `for` loop, but never use it. There is a minor syntax error (`for my $i in` should just be `for my $i`). You pass -9 to kill, but this should probably be 9 (the negative signal has a different meaning than it does to the shell command `kill`). Fixing these, I would probably write it as follows: `my $child = fork; if ($child) { # I am in the parent...wait then kill for (1..10) { sleep 1; print "."; } kill 9, $child; } else { # Run the background program exec '/path/to/program > /dev/null 2>&1'; }` [download] Update: an alternative method that avoids explicit forking, and perhaps looks a bit more Perlish: `my $pid = open my $cmdfh, "-\|", '/path/to/program' or die "Cannot fork: $!\n"; for ( 1 .. 10 ) { print "."; sleep 1; } kill 9, $pid;` [download]	[reply] [d/l] [select]
Re^3: Executing a program, displaying some status, and killing it by Spida (Acolyte) on Dec 12, 2004 at 16:58 UTC
Both versions work, but not the way I want... the status output (print ".") appears only after the background-program has been killed, which makes it pretty useless...	[reply]
Re^4: Executing a program, displaying some status, and killing it by revdiablo (Prior) on Dec 13, 2004 at 17:53 UTC
the status output (print ".") appears only after the background-program has been killed That's probably a buffering problem. The short answer is to set `$\|`, the long answer is to read Suffering from Buffering.	[reply] [d/l]