$ ./6.fork.pl
relevant processes with pstree command:
6.fork.pl,6800 -w ./6.fork.pl
  |-6.fork.pl,6801 -w ./6.fork.pl
  |   `-sh,6803 -c ping www.google.com >5.fork.txt
  |       `-ping,6804 www.google.com
  `-pstree,6802 -Apal 6800
6801 terminated
PING www.google.com(sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004)) 56 data bytes
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=1 ttl=54 time=141 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=2 ttl=54 time=17.8 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=3 ttl=54 time=33.0 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=4 ttl=54 time=31.7 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=5 ttl=54 time=28.0 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=6 ttl=54 time=34.9 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=7 ttl=54 time=25.0 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=8 ttl=54 time=19.7 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=9 ttl=54 time=18.2 ms
64 bytes from sea15s07-in-x04.1e100.net (2607:f8b0:400a:800::2004): icmp_seq=10 ttl=54 time=39.5 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=144 ttl=54 time=18.5 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=145 ttl=54 time=271 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=146 ttl=54 time=346 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=147 ttl=54 time=35.9 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=148 ttl=54 time=205 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=149 ttl=54 time=42.1 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=150 ttl=54 time=168 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=151 ttl=54 time=20.5 ms
64 bytes from sea15s11-in-x04.1e100.net (2607:f8b0:400a:808::2004): icmp_seq=152 ttl=54 time=377 ms
10? <-ten seconds elapsed from forked process