kill: signal names only understood in uppercase, should accept all casings

[BenWiederhake]

(Originally documented in #6202)

$ cargo run --features kill kill -l sIgUsR2
kill: unknown signal name 'sIgUsR2'
[$? = 1]
$ kill -l sIgUsR2 # bash built-in
12
$ /usr/bin/kill -l sIgUsR2 # Debian procps-ng 4.0.4
12

TODO: I assume GNU 9.5 kill also behaves like that, but I can't check right now

[cakebaker]

Yes, GNU kill behaves in the same way.

[m-haisham]

Does the old form also accept non uppercase signal names? I assume not

[BenWiederhake]

If by "old form" you mean just the signal name without the "SIG" prefix, then yes, it does accept it:

$ sleep 999 &
[1] 2037120
$ kill -s uSr1 2037120  # bash builtin
[1]+  Benutzerdefiniertes Signal 1    sleep 999
$ sleep 999 &
[1] 2037165
$ /usr/bin/kill -s uSr1 2037165  # Debian procps-ng
[1]+  Benutzerdefiniertes Signal 1    sleep 999
$ sleep 999 &
[1] 2037174
$ ../gnu/src/kill -s uSr1 2037174  # GNU 9.5
[1]+  Benutzerdefiniertes Signal 1    sleep 999
$