[PATCH] kill: add '--' option to separate options from arguments

[Ron Yorston]

Using a negative pid to send TERM to a process group results in an
obscure error:

   $ ./busybox kill -12345
   kill: bad signal name '12345'

There are a couple of workarounds:

- specify the signal: 'kill -TERM -12345'

- use the 'shell hack' and add a leading space to the argument:
  'kill " -12345"'.  This only works if the shell hack is enabled.

The full versions of kill and killall provide a '--' argument to
separate options from arguments.  Add this capability to BusyBox.

This doesn't avoid the need for the shell hack, which is only partly
about handling arguments that start with a dash:  it also packs multiple
pids into a single argument.

bloat-o-meter gives the somewhat unbelievable result:

function                                             old     new   delta
kill_main                                            993     999      +6
packed_usage                                       32073   32047     -26
.rodata                                           164190  164164     -26
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 6/-52)             Total: -46 bytes
   text	   data	    bss	    dec	    hex	filename
 872711	   4110	   1944	 878765	  d68ad	busybox_old
 872691	   4110	   1944	 878745	  d6899	busybox_unstripped

A few more changes like that and BusyBox will take a negative amount
of disk space.

Signed-off-by: Ron Yorston <rmy at pobox.com>
---
 procps/kill.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/procps/kill.c b/procps/kill.c
index 0ddae2f70..e085f4d56 100644
--- a/procps/kill.c
+++ b/procps/kill.c
@@ -42,7 +42,7 @@
 //kbuild:lib-$(CONFIG_KILLALL5) += kill.o
 
 //usage:#define kill_trivial_usage
-//usage:       "[-l] [-SIG] PID..."
+//usage:       "[-l] [-SIG] [--] PID..."
 //usage:#define kill_full_usage "\n\n"
 //usage:       "Send a signal (default: TERM) to given PIDs\n"
 //usage:     "\n	-l	List all signal names and numbers"
@@ -59,7 +59,7 @@
 //usage:       "$ kill 252\n"
 //usage:
 //usage:#define killall_trivial_usage
-//usage:       "[-l] [-q] [-SIG] PROCESS_NAME..."
+//usage:       "[-l] [-q] [-SIG] [--] PROCESS_NAME..."
 //usage:#define killall_full_usage "\n\n"
 //usage:       "Send a signal (default: TERM) to given processes\n"
 //usage:     "\n	-l	List all signal names and numbers"
@@ -184,6 +184,10 @@ int kill_main(int argc UNUSED_PARAM, char **argv)
 	if (is_killall5 && arg[0] == 'o')
 		goto do_it_now;
 
+	/* -- separates options from arguments */
+	if (!is_killall5 && arg[0] == '-')
+		goto do_it_sooner;
+
 	if (argv[1] && arg[0] == 's' && arg[1] == '\0') { /* -s SIG? */
 		arg = *++argv;
 	} /* else it must be -SIG */
@@ -192,6 +196,7 @@ int kill_main(int argc UNUSED_PARAM, char **argv)
 		bb_error_msg("bad signal name '%s'", arg);
 		return EXIT_FAILURE;
 	}
+ do_it_sooner:
 	arg = *++argv;
 
  do_it_now:
-- 
2.13.5