external command timeout 2

[nychris]

I have a large list of servers in @servers that I loop through and run a command on.

chomp(@out = `/some/command`);

Sometimes there will be something up with one of the servers and the command never finished which effectively hangs the script indefinitely. Is there a way to time this out after x amount of seconds?

 

[travs69]

look at the alarm function, it works great for those kind of issues..

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Travis - Those who say it cannot be done are usually interrupted by someone else doing it; Give the wrong symptoms, get the wrong solutions;

 

[Kirsle]

eval {
  local $SIG{ALRM} = sub { die; }
  alarm(30); # 30 seconds
  system("/usr/bin/may-or-may-not-return");
  alarm(0); # turn off the alarm clock
};
if ($@) {
  warn "command timed out";
}

Kirsle.net | My personal homepage

perl -e '$|=$i=1;print" oo\n<|>\n_|_";x:sleep$|;print"\b",$i++%2?"/":"_";goto x;'

 

[travs69]

will $@ ever print because you are dieing in the sub?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Travis - Those who say it cannot be done are usually interrupted by someone else doing it; Give the wrong symptoms, get the wrong solutions;

 

[Kirsle]

If an eval crashes (on purpose via die, on accident via dividing by zero etc), $@ is set to the error message ("Illegal division by zero at (eval 1) line X"... or "Alarm clock" in this case).

If eval exits successfully $@ is undef.

This is like Perl's version of try/catch. ;-)

Kirsle.net | My personal homepage

perl -e '$|=$i=1;print" oo\n<|>\n_|_";x:sleep$|;print"\b",$i++%2?"/":"_";goto x;'

 

[Kirsle]

Er.. if you were asking about the "sub { die; }" part...

Even if it dies in a sub, a die would normally kill the entire program. Since the sub is inside the eval, the die doesn't kill the entire program but falls into the jurisdiction of the eval; it kills only the block of eval code and sets $@ to the error text.

Kirsle.net | My personal homepage

perl -e '$|=$i=1;print" oo\n<|>\n_|_";x:sleep$|;print"\b",$i++%2?"/":"_";goto x;'

 

[travs69]

Thanks.. that's what I was wondering about, I only use evals for the alarm function and I normally don't die there if the command fails but exit later after I clean up all my connections (db's, open files, shared memory, etc).

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Travis - Those who say it cannot be done are usually interrupted by someone else doing it; Give the wrong symptoms, get the wrong solutions;

 

[nychris]

Kirsle, this is awesome and will be very helpful! I've been looking for a way to do this for some time. I have to loop through about 2000 servers and there's always one or two that will hang and kill the entire script. Thanks!