This file is fg_bg.def, from which is created fg_bg.c.
It implements the builtins "bg" and "fg" 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 fg_bg.c

$BUILTIN fg
$FUNCTION fg_builtin
$DEPENDS_ON JOB_CONTROL
$SHORT_DOC fg [job_spec]
Place JOB_SPEC in the foreground, and make it the current job.  If
JOB_SPEC is not present, the shell's notion of the current job is
used.
$END

#include <sys/types.h>
#include <signal.h>
#include "../shell.h"
#include "../jobs.h"

#if defined (JOB_CONTROL)
extern char *this_command_name;

static int fg_bg ();

/* How to bring a job into the foreground. */
int
fg_builtin (list)
     WORD_LIST *list;
{
  int fg_bit = 1;
  register WORD_LIST *t = list;

  if (!job_control)
    {
      builtin_error ("no job control");
      return (EXECUTION_FAILURE);
    }

  /* If the last arg on the line is '&', then start this job in the
     background.  Else, fg the job. */

  while (t && t->next)
    t = t->next;

  if (t && t->word->word[0] == '&' && !t->word->word[1])
    fg_bit = 0;

  return (fg_bg (list, fg_bit));
}
#endif /* JOB_CONTROL */

$BUILTIN bg
$FUNCTION bg_builtin
$DEPENDS_ON JOB_CONTROL
$SHORT_DOC bg [job_spec]
Place JOB_SPEC in the background, as if it had been started with
`&'.  If JOB_SPEC is not present, the shell's notion of the current
job is used.
$END

#if defined (JOB_CONTROL)
/* How to put a job into the background. */
int
bg_builtin (list)
     WORD_LIST *list;
{
  if (!job_control)
    {
      builtin_error ("no job control");
      return (EXECUTION_FAILURE);
    }

  return (fg_bg (list, 0));
}

/* How to put a job into the foreground/background. */
static int
fg_bg (list, foreground)
     WORD_LIST *list;
     int foreground;
{
  sigset_t set, oset;
  int job, status = EXECUTION_SUCCESS, old_async_pid;

  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 ? list->word->word : "");

      goto failure;
    }

  /* Or if jobs[job]->pgrp == shell_pgrp. */
  if (!(jobs[job]->flags & J_JOBCONTROL))
    {
      builtin_error ("job %%%d started without job control", job + 1);
      goto failure;
    }

  if (!foreground)
    {
      old_async_pid = last_asynchronous_pid;
      last_asynchronous_pid = jobs[job]->pgrp;	/* As per Posix.2 5.4.2 */
    }

  status = start_job (job, foreground);

  if (status >= 0)
    {
    /* win: */
      UNBLOCK_CHILD (oset);
      return (status);
    }
  else
    {
      if (!foreground)
	last_asynchronous_pid = old_async_pid;

    failure:
      UNBLOCK_CHILD (oset);
      return (EXECUTION_FAILURE);
    }
}
#endif /* JOB_CONTROL */