What does `exit_status` mean in `kill -l [exit_status]`?

Question

kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid

kill -l [exit_status]

Send a signal specified by sigspec or signum to the process named by job specification jobspec or process id pid. sigspec is either a case-insensitive signal name such as SIGINT (with or without the SIG prefix) or a signal number; signum is a signal number. If sigspec and signum are not present, SIGTERM is used. The -l option lists the signal names. If any arguments are supplied when -l is given, the names of the signals corresponding to the arguments are listed, and the return status is zero. exit status is a number specifying a signal number or the exit status of a process terminated by a signal. The return status is zero if at least one signal was successfully sent, or non-zero if an error occurs or an invalid option is encountered.

I was wondering what kind of value exit_status can take?

What does "exit status is a number specifying a signal number or the exit status of a process terminated by a signal" mean?

Answer 1

Just exactly as the text says, you can supply one of two things:

• a number specifying a signal number: the signals are numbered 1, 2, 3, etc... (as you can see from the usage message for the common invocation). So you can ask kill -l to give you the name corresponding to such a number.
• the exit status of a process terminated by a signal: when processes are killed by a signal, they get a special exit status that is (usually? always?) 128 + the signal number that caused them to die. So you can ask kill -l to document that too.