waitpid
Wait for arbitrary processes to terminate
TLDR
Wait for processes to exit
$ waitpid [pid1] [pid2]
Wait with timeout$ waitpid -t [n] [pid1] [pid2]
Ignore already exited processes$ waitpid -e [pid1] [pid2]
Wait for N processes$ waitpid -c [n] [pid1] [pid2]
Display help$ waitpid -h
SYNOPSIS
waitpid [OPTIONS] PID...
DESCRIPTION
waitpid waits for the termination of arbitrary processes by their PIDs. Unlike the shell built-in wait, it can wait for any process, not just children of the current shell.
The command blocks until all specified processes have terminated or the timeout expires.
PARAMETERS
-t, --timeout SECONDS
Maximum time to wait-e, --exited
Don't error if PIDs have already exited-c, --count N
Wait until N processes have exited-h, --help
Display help information
CAVEATS
Part of util-linux. Can only monitor processes visible to the current user. Requires appropriate permissions to monitor processes.