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(TLDR Doug O'Neal's strace -f -e execve ./myprogram solved me problem)

I start a program on the command line. The executing program spawns processes. I would like to see or log the names of all processes spawned by the program.

Details

I've tried top with forest view V:

$ top -c -d 1

Only the parent program is briefly visible. I suspect the refresh rate is too slow to show the child processes.

I've tried to filter by COMMAND=myprogram but this most probably filters out the child processes.

The parent program spawns processes but I am not sure if top's forest view will show those new processes indented under the original process or independently. I'm not sure if a spawned process can be independent of the parent.

Update #1

I tried this answer with the sleep removed.

#!/bin/bash mkdir -p "$HOME/ps_logs" while true; do ps faux > "$HOME/ps_logs/ps_$(date +%Y-%m-%d_%H:%M:%S).log" done

I filtered the output with:

grep -rnw './' -e 'myprogam'

All the files only contain myprogram. So how do I know if myprogram even spawns any processes?

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  • 1
    Have you tried pstree? Commented Jul 5, 2018 at 12:08
  • How should I employ pstree? The program I'm analysing finishes in under a second. pstree shows running processes. I'm looking for something that logs the spawned processes as the program runs. Commented Jul 5, 2018 at 12:13
  • 1
    Well you could background the parent, and use $! to immediately get its PID to pass to pstree e.g. ./yourprog & pstree -p $! Commented Jul 5, 2018 at 12:24
  • 6
    Maybe strace -f -e execve ./myprogram ? Doesn't have the problem of trying to shell out another command before your program actually exits. Commented Jul 5, 2018 at 12:53
  • 1
    Yeah or see How to track child process using strace? Commented Jul 5, 2018 at 12:56

1 Answer 1

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I generally like using ps auxf because it visually shows the child processes under the parent visually:

$ ps auxf ... root 637 0.0 0.0 110044 800 tty1 Ss+ 02:50 0:00 /sbin/agetty --noclear tty1 linux root 983 0.0 0.1 404028 1136 ? Sl 02:50 0:11 /usr/sbin/VBoxService --pidfile /var/run/vboxadd-service.sh root 1013 0.0 1.6 562416 16444 ? Ssl 02:50 0:03 /usr/bin/python -Es /usr/sbin/tuned -l -P root 1015 0.0 0.4 105996 4108 ? Ss 02:50 0:00 /usr/sbin/sshd -D root 20191 0.0 0.5 152116 5576 ? Ss 10:06 0:00 \_ sshd: vagrant [priv] vagrant 20193 0.0 0.2 152304 2872 ? S 10:06 0:00 \_ sshd: vagrant@pts/0 vagrant 20194 0.0 0.2 115964 2644 pts/0 Ss 10:06 0:00 \_ -bash root 20232 0.0 0.2 201844 2956 pts/0 S 10:06 0:00 \_ sudo -Es root 20233 0.0 0.2 116208 2964 pts/0 S 10:06 0:00 \_ /bin/bash root 20510 0.0 0.1 151240 1932 pts/0 R+ 11:01 0:00 \_ ps auxf root 1115 0.0 0.2 91628 2192 ? Ss 02:50 0:00 /usr/libexec/postfix/master -w postfix 1117 0.0 0.3 91800 4048 ? S 02:50 0:00 \_ qmgr -l -t unix -u postfix 20149 0.0 0.3 91776 4048 ? S 09:39 0:00 \_ pickup -l -t unix -u ...

Additionally if you just want to view the list of PID + PGID you can use ps with these switches like so:

$ ps x -o "%p %r %c" PID PGID COMMAND 1 1 systemd 2 0 kthreadd 3 0 ksoftirqd/0 5 0 kworker/0:0H 7 0 migration/0 8 0 rcu_bh ... ... 591 591 rngd 594 594 systemd-logind 596 596 smartd 597 597 rsyslogd 600 600 acpid 616 616 abrtd 617 617 abrt-watch-log 630 630 atd 637 637 agetty 983 981 VBoxService 1013 1013 tuned 1015 1015 sshd 1115 1115 master 2426 2426 NetworkManager 2439 2439 dhclient 3123 3123 firewalld 3828 0 kworker/u2:1
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