Question

I have a perl script which has to make a call to tar within an exec.

exec("tar zcf /tmp/mytarball.gz directoryToTarBall > /dev/null 2>&1" or die ("$!")

This is a child process which I have forked and in the meantime, I’m monitoring the progress of the tar by writing a full stop to STDOUT. The problem I have is that I don’t want tar to be verbose when creating the tarball – i dont want output to be echoed to stdout….I just want the progress counter (the full stops) echoing back to screen. I thought I could pass a >/dev/null 2>&1 within the exec command but that didn’t work.

Any ideas greatly received. Thanks and regards

Answer 1

Use the exec LIST form to avoid surprises due to shell quoting. This also requires performing the redirection that the shell would do for you.

use 5.10.0;  # //

my $pid = fork // die "$0: fork: $!";   # / fix Stack Overflow highlighting
if ($pid) {
  waitpid $pid, 0 or die "$0: waitpid: $!";
  warn "$0: child exited abnormally" if $?;
  print ".\n";  # done!
}
else {
  open STDOUT, ">",  "/dev/null" or die "$0: open: $!";
  open STDERR, ">&", \*STDOUT    or exit 1;
  exec "tar", "zcf", "/tmp/mytarball.gz", "directoryToTarBall";
  exit 1;
}