This file is kill.def, from which is created kill.c.
It implements the builtin "kill" in Bash.

Copyright (C) 1987, 1989, 1991 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any later
version.

Bash is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

$PRODUCES kill.c

$BUILTIN kill
$FUNCTION kill_builtin
$DEPENDS_ON JOB_CONTROL
$SHORT_DOC kill [-s sigspec | -sigspec] [pid | job]... | -l [signum]
Send the processes named by PID (or JOB) the signal SIGSPEC.  If
SIGSPEC is not present, then SIGTERM is assumed.  An argument of `-l'
lists the signal names; if arguments follow `-l' they are assumed to
be signal numbers for which names should be listed.  Kill is a builtin
for two reasons: it allows job ID's to be used instead of pids, and if
you run out of processes, you can still kill them.
$END

#include <sys/types.h>
#include <errno.h>
extern int errno;

#include "../shell.h"
#include "../trap.h"
#include "../jobs.h"

#if defined (JOB_CONTROL)
extern int job_control;

#if !defined (CONTINUE_AFTER_KILL_ERROR)
#  define CONTINUE_OR_FAIL return (EXECUTION_FAILURE)
#else
#  define CONTINUE_OR_FAIL goto continue_killing
#endif /* CONTINUE_AFTER_KILL_ERROR */

/* Here is the kill builtin.  We only have it so that people can type
   kill -KILL %1?  No, if you fill up the process table this way you
   can still kill some. */
int
kill_builtin (list)
     WORD_LIST *list;
{
  int signal = SIGTERM;
  int any_succeeded = 0, listing = 0, saw_signal = 0;
  char *sigspec;
  pid_t pid;

  if (!list)
    return (EXECUTION_SUCCESS);

  /* Process options. */
  while (list)
    {
      if (strcmp (list->word->word, "-l") == 0)
	{
	  listing++;
	  list = list->next;
	}
      else if (strcmp (list->word->word, "-s") == 0)
	{
	  list = list->next;
	  if (list)
	    {
	      sigspec = list->word->word;
	      if (strcmp (sigspec, "0") == 0)
		signal = 0;
	      else
		signal = decode_signal (sigspec);
	      list = list->next;
	    }
	  else
	    {
	      builtin_error ("-s requires an argument");
	      return (EXECUTION_FAILURE);
	    }
	}
      else if (strcmp (list->word->word, "--") == 0)
	{
	  list = list->next;
	  break;
	}
      /* If this is a signal specification then process it.  We only process
	 the first one seen; other arguments may signify process groups (e.g,
	 -num == process group num). */
      else if ((*(list->word->word) == '-') && !saw_signal)
	{
	  sigspec = &(list->word->word)[1];
	  signal = decode_signal (sigspec);
	  saw_signal++;
	  list = list->next;
	}
      else
	break;
    }

  if (listing)
    {
      if (!list)
	{
	  register int i, column = 0;
	  for (i = 1; i < NSIG; i++)
	    {
	      char *name = signal_name (i);
	      if ((strncmp (name, "SIGJUNK", 7) == 0) ||
		  (strncmp (name, "Unknown", 7) == 0))
		continue;

	      printf ("%2d) %s", i, name);

	      if (++column < 4)
		printf ("\t");
	      else
		{
		  printf ("\n");
		  column = 0;
		}
	    }

	  if (column != 0)
	    printf ("\n");
	}
      else
	{
	  /* List individual signal names. */
	  while (list)
	    {
	      int signum;
	      char *name;

	      if ((sscanf (list->word->word, "%d", &signum) != 1) ||
		  (signum <= 0))
		{
	    list_error:
		  builtin_error ("bad signal number: %s", list->word->word);
		  list = list->next;
		  continue;
		}

	      /* This is specified by Posix.2 so that exit statuses can be
		 mapped into signal numbers. */
	      if (signum > 128)
		signum -= 128;

	      if (signum > NSIG)
		goto list_error;

	      name = signal_name (signum);
	      if ((strncmp (name, "SIGJUNK", 7) == 0) ||
		  (strncmp (name, "Unknown", 7) == 0))
		{
		  list = list->next;
		  continue;
		}
	      printf ("%s\n", name);
	      list = list->next;
	    }
	}
      return (EXECUTION_SUCCESS);
    }

  /* OK, we are killing processes. */
  if (signal == NO_SIG)
    {
      builtin_error ("bad signal spec `%s'", sigspec);
      return (EXECUTION_FAILURE);
    }

  while (list)
    {
      char *word = list->word->word;

      if (*word == '-')
	word++;

      if (all_digits (word))
	{
	  /* Use the entire argument in case of minus sign presence. */
	  pid = (pid_t) atoi (list->word->word);

	  if (kill_pid (pid, signal, 0) < 0)
	    goto signal_error;
	  else
	    any_succeeded++;
	}
      else if (*list->word->word != '%')
	{
	  builtin_error ("No such pid %s", list->word->word);
	  CONTINUE_OR_FAIL;
	}
      else if (job_control)	/* can't kill jobs if not using job control */
	{			/* Must be a job spec.  Check it out. */
	  int job;
	  sigset_t set, oset;

	  BLOCK_CHILD (set, oset);
	  job = get_job_spec (list);

	  if (job < 0 || job >= job_slots || !jobs[job])
	    {
	      if (job != DUP_JOB)
		builtin_error ("No such job %s", list->word->word);
	      UNBLOCK_CHILD (oset);
	      CONTINUE_OR_FAIL;
	    }

	  /* Job spec used.  Kill the process group. If the job was started
	     without job control, then its pgrp == shell_pgrp, so we have
	     to be careful.  We take the pid of the first job in the pipeline
	     in that case. */
	  if (jobs[job]->job_control)
	    pid = jobs[job]->pgrp;
	  else
	    pid = jobs[job]->pipe->pid;

	  UNBLOCK_CHILD (oset);

	  if (kill_pid (pid, signal, 1) < 0)
	    {
	    signal_error:
	      if (errno == EPERM)
		builtin_error ("(%d) - Not owner", (int)pid);
	      else if (errno == ESRCH)
		builtin_error ("(%d) - No such pid", (int)pid);
	      else
		builtin_error ("Invalid signal %d", signal);
	      CONTINUE_OR_FAIL;
	    }
	  else
	    any_succeeded++;
	}
      else
	{
	  builtin_error ("bad process specification `%s'", list->word->word);
	  CONTINUE_OR_FAIL;
	}
    continue_killing:
      list = list->next;
    }

  if (any_succeeded)
    return (EXECUTION_SUCCESS);
  else
    return (EXECUTION_FAILURE);
}
#endif /* JOB_CONTROL */