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Old 09-14-2006, 08:55 PM   #1
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how to run perl pgm in background??


I've a perl pgm that calls another perl that could run about an hour. So I want the 1st perl to call 2nd perl to run in the background while I set some timer in the 1st perl to loop, say every 5 minutes to tell me the 2nd perl is still running. Any help would be appreciated.

Old 09-14-2006, 11:27 PM   #2
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I've no idea about perl but generally on linux you can make process work on the background by issuing it with ampersand "commmand &".
Hope this helps.
Old 09-15-2006, 03:46 AM   #3
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I have to ask - why do you want to bother doing all that just to get prog1 to tell you prog2 is still running? If you execute prog2 in the foreground, then prog1 won't return until prog2 finishes, so there's nothing to do! You know prog2 is still running because prog1 is still running...
Old 09-15-2006, 09:19 AM   #4
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The most common way would to be to fork the first program:

# If $pid is undefined, fork was not successful.
if( ! defined( $pid = fork ) ) {
return $pid;
} elsif( $pid ) {
# If $pid is greater than 0, this is the parent fork and
# $pid is the child's pid
# Create a second kid to kill the first if running too long
if( $type eq "LOG" || $type eq "MONITOR" ) { timeout( $pid ); }
return $pid; # i'm the parent

Then the first program can run some timeout stuff:

sub timeout {
my $sibling = shift;
my $pid;
my $i;

# If $pid is undefined, fork was not successful.
if( ! defined( $pid = fork ) ) {
return $pid;
} elsif( $pid ) {
# If $pid is greater than 0, this is the parent fork and
# $pid is the child's pid
return $pid; # i'm the parent

# Else if $pid is 0, this is the child fork
# Pause for awhile then check the other process
for( my $x = 0; $x < 10; ++$x ) {
# See if the sibling is still alive by sending kill 0 signal.
# If it's dead, kill yourself
exit unless ( kill 0 => $sibling );
# Pause a sec
sleep( 1 );

# See if the sibling is still alive by sending kill 0 signal.
# If it is still alive, kill it because the time is up
if( kill 0 => $sibling ) { $sibling = kill KILL => $sibling; }


Check the perldocs by typing 'perldoc -f fork'.

Hope this helps.
Old 09-15-2006, 02:33 PM   #5
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Thank you ALL for the quick reply. I've tried with the "&" a bit with no luck yet. The reason for this is someone else is running the program. I want to give a job status every so often to anyone looking at the console. It is very easy for a person to enter a ctl-c to end the process if he/she thinks something got hung. Thank you eblack for the sample program. I'll give it a try.
Old 09-22-2006, 08:22 AM   #6
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1. You can use perl system() function
someyhing like => system(/usr/bin/perl &); => for background running.
2. You can check the status in loop using
system(pidof => If its giving some value that means its running else would be blank return

Good Luck.


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