Quiz: what a process is doing

Read the output

The mailer service is alive but doing nothing. What is it waiting for?

$ sudo timeout 3 strace -p 1022
strace: Process 1022 attached
flock(4, LOCK_EX
$ sudo ls -l /proc/1022/fd
lr-x------ 1 root root 64 Oct 20 23:42 0 -> /dev/null
lrwx------ 1 root root 64 Oct 20 23:42 1 -> socket:[7831]
lrwx------ 1 root root 64 Oct 20 23:42 2 -> socket:[7831]
l-wx------ 1 root root 64 Oct 20 23:42 3 -> /var/log/mailer.log
l-wx------ 1 root root 64 Oct 20 23:42 4 -> /var/lib/mailer/queue.lock

• A An answer from the journal socket.
• B The lock on /var/lib/mailer/queue.lock.
• C A chance to write to /var/log/mailer.log.