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How do find the total number of child processes (recursively) spawned by a script?

For profiling purposes, it is sometimes important to count the generated sub-processes of command, script, etc.

What I tried?

  • ps based solutions -- but it just presents the current running processes.
  • using the next pid number (this is my best solution)

example:

ps | awk '/ ps$/{print $1}'
27159
$ for a in {1..100} ; do date > /dev/null; done  ## 100 processes
$ ps | awk '/ ps$/{print $1-2}'
27259

(27259-27159=100) but the next pid number is reseted and suffers the interference of other tasks.

1 Answer 1

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> strace -c -f -e trace=fork,vfork,clone,execve,execl bash -c 'ls -ld /etc;sleep 1'
Process 15683 attached
drwxr-xr-x 1 root root 5540 10. Jan 02:08 /etc
Process 15684 attached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         2           clone
  0.00    0.000000           0         3           execve
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                     5           total

> strace -c -f -e trace=fork,clone,execve bash -c '(foo=bar;ls -ld /etc);sleep 1'
Process 15730 attached
Process 15731 attached
drwxr-xr-x 1 root root 5540 10. Jan 02:08 /etc
Process 15732 attached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         3           clone
  0.00    0.000000           0         3           execve
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                     6           total
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  • This is what I was looking for. Thank you very much! (in my fedora20 machine I had to remove "execl" but I was expecting minor differences between Unix variants)
    – JJoao
    Commented Jan 11, 2015 at 21:45

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