The parent perl script - parent.pl
---------------------------------------
#!/usr/bin/perl

print "I AM PARENT\n";

my $x=`/root/a.sh`;
#my $x=`/root/b.pl`;
#my $x=`/root/a.out`;
#my $x=system("/root/a.sh");

print "PARENT EXITING\n";

Child script - a.sh
---------------------
#!/bin/sh

echo "I am a.sh......."
sleep 6000
echo "I am gonna die ........"
exit 123


Another child script but which is perl instead of bash - b.pl
---------------------------------------------------------------------
#!/usr/bin/perl

print "I am b.pl\n";
sleep(6000000);
print "I am gonna die...\n";

##</code><code>##


[root@onong ~]# ps aux | grep a.sh
root 23171 0.0 0.0 63860 1084 pts/4 S+ 03:12 0:00 /bin/sh /root/a.sh
root 23514 0.0 0.0 61176 804 pts/2 S+ 03:12 0:00 grep a.sh
[root@onong ~]# kill 23171
[root@onong ~]# ps aux | grep a.sh
root 23171 0.0 0.0 0 0 pts/4 Z+ 03:12 0:00 [a.sh] <defunct> <----------------------- CHILD BECOMES ZOMBIE
root 23967 0.0 0.0 61176 804 pts/2 S+ 03:13 0:00 grep a.sh
[root@onong ~]#

Strace output of the parent process:

[root@onong ~]# strace ./test.pl
.
.
.
open("./test.pl", O_RDONLY) = 3
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff24ed2260) = -1 ENOTTY (Inappropriate ioctl for device)
lseek(3, 0, SEEK_CUR) = 0
fcntl(3, F_SETFD, FD_CLOEXEC) = 0
fstat(3, {st_mode=S_IFREG|0755, st_size=160, ...}) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
readlink("/proc/self/exe", "/usr/bin/perl"..., 4095) = 13
brk(0x170a1000) = 0x170a1000
read(3, "#!/usr/bin/perl\n\nprint \"I AM PAR"..., 4096) = 160
read(3, "", 4096) = 0
close(3) = 0
write(1, "I AM PARENT\n", 12I AM PARENT
) = 12
pipe([3, 4]) = 0
pipe([5, 6]) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x2b61c66692e0) = 23171 <--------- CHILD SPAWNED
close(6) = 0
close(4) = 0
read(5, "", 4) = 0
close(5) = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff24ed21a0) = -1 EINVAL (Invalid argument)
lseek(3, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
fstat(3, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
read(3, "I am a.sh.......\n", 4096) = 17
read(3, 0x17082210, 4096) = ? ERESTARTSYS (To be restarted) <-------------- DOESN"T RETURN 0
--- SIGCHLD (Child exited) @ 0 (0) ---
read(3, <----------------- KEEPS WAITING IN READ(2)

##</code><code>##

[root@onong ~]# ps aux | grep b.pl
root 29350 0.0 0.0 77884 1488 pts/4 S+ 03:15 0:00 /usr/bin/perl /root/b.pl
root 29495 0.0 0.0 61176 756 pts/2 S+ 03:15 0:00 grep b.pl
[root@onong ~]# kill 29350
[root@onong ~]# ps aux | grep b.pl
root 30028 0.0 0.0 61176 748 pts/2 S+ 03:16 0:00 grep b.pl
[root@onong ~]#

Strace of parent process:

read(3, "#!/usr/bin/perl\n\nprint \"I AM PAR"..., 4096) = 160
read(3, "", 4096) = 0
close(3) = 0
write(1, "I AM PARENT\n", 12I AM PARENT
) = 12
pipe([3, 4]) = 0
pipe([5, 6]) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x2ba7aabac2e0) = 29350
close(6) = 0
close(4) = 0
read(5, "", 4) = 0
close(5) = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff4156e300) = -1 EINVAL (Invalid argument)
lseek(3, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
fstat(3, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
read(3, "", 4096) = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
close(3) = 0
rt_sigaction(SIGHUP, {0x1, [], SA_RESTORER, 0x343740e7c0}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, {0x1, [], SA_RESTORER, 0x343740e7c0}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, {0x1, [], SA_RESTORER, 0x343740e7c0}, {SIG_DFL, [], 0}, 8) = 0
wait4(29350, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGTERM}], 0, NULL) = 29350
rt_sigaction(SIGHUP, {SIG_DFL, [], SA_RESTORER, 0x343740e7c0}, NULL, 8) = 0
rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x343740e7c0}, NULL, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, [], SA_RESTORER, 0x343740e7c0}, NULL, 8) = 0
write(1, "PARENT EXITING\n", 15PARENT EXITING
) = 15
exit_group(0) = ?