xref: /src/bin/sh/jobs.c

/*	$NetBSD: jobs.c,v 1.122.2.1 2025/08/02 05:18:26 perseant Exp $	*/

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)jobs.c	8.5 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: jobs.c,v 1.122.2.1 2025/08/02 05:18:26 perseant Exp $");
#endif
#endif /* not lint */

#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <paths.h>
#include <sys/types.h>
#include <sys/param.h>
#ifdef BSD
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#endif
#include <sys/ioctl.h>

#include "shell.h"
#if JOBS
#if OLD_TTY_DRIVER
#include "sgtty.h"
#else
#include <termios.h>
#endif
#undef CEOF			/* syntax.h redefines this */
#endif
#include "redir.h"
#include "show.h"
#include "main.h"
#include "parser.h"
#include "nodes.h"
#include "jobs.h"
#include "var.h"
#include "options.h"
#include "builtins.h"
#include "trap.h"
#include "syntax.h"
#include "input.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "mystring.h"


#ifndef	WCONTINUED
#define	WCONTINUED 0		/* So we can compile on old systems */
#endif
#ifndef	WIFCONTINUED
#define	WIFCONTINUED(x)	(0)		/* ditto */
#endif


static struct job *jobtab;		/* array of jobs */
static int njobs;			/* size of array */
static int jobs_invalid;		/* set in child */
MKINIT pid_t backgndpid = -1;	/* pid of last background process */
#if JOBS
int initialpgrp;		/* pgrp of shell on invocation */
static int curjob = -1;		/* current job */
#endif
static int ttyfd = -1;

STATIC void restartjob(struct job *);
STATIC void freejob(struct job *);
STATIC struct job *getjob(const char *, int);
STATIC int dowait(int, struct job *, struct job **);
#define WBLOCK	1
#define WNOFREE 2
#define WSILENT 4
STATIC int jobstatus(const struct job *, int);
STATIC int waitproc(int, struct job *, int *);
STATIC int cmdtxt(union node *, int);
STATIC void cmdlist(union node *, int);
STATIC void cmdputs(const char *);
inline static void cmdputi(int);

#define	JNUM(j)	((int)((j) != NULL ? ((j) - jobtab) + 1 : 0))

#ifdef SYSV
STATIC int onsigchild(void);
#endif

#ifdef OLD_TTY_DRIVER
static pid_t tcgetpgrp(int fd);
static int tcsetpgrp(int fd, pid_t pgrp);

static pid_t
tcgetpgrp(int fd)
{
	pid_t pgrp;
	if (ioctl(fd, TIOCGPGRP, (char *)&pgrp) == -1)
		return -1;
	else
		return pgrp;
}

static int
tcsetpgrp(int fd, pid_tpgrp)
{
	return ioctl(fd, TIOCSPGRP, (char *)&pgrp);
}
#endif

static void
ttyfd_change(int from, int to)
{
	if (ttyfd == from)
		ttyfd = to;
}

/*
 * Turn job control on and off.
 *
 * Note:  This code assumes that the third arg to ioctl is a character
 * pointer, which is true on Berkeley systems but not System V.  Since
 * System V doesn't have job control yet, this isn't a problem now.
 */

MKINIT int jobctl;

void
setjobctl(int on)
{
#ifdef OLD_TTY_DRIVER
	int ldisc;
#endif

	if (on == jobctl || rootshell == 0)
		return;
	if (on) {
#if defined(FIOCLEX) || defined(FD_CLOEXEC)
		int i;

		if (ttyfd != -1)
			sh_close(ttyfd);
		if ((ttyfd = open("/dev/tty", O_RDWR)) == -1) {
			for (i = 0; i < 3; i++) {
				if (isatty(i) && (ttyfd = dup(i)) != -1)
					break;
			}
			if (i == 3)
				goto out;
		}
		ttyfd = to_upper_fd(ttyfd);	/* Move to a high fd */
		register_sh_fd(ttyfd, ttyfd_change);
#else
		out2str("sh: Need FIOCLEX or FD_CLOEXEC to support job control");
		goto out;
#endif
		if ((initialpgrp = tcgetpgrp(ttyfd)) < 0) {
 out:
			out2str("sh: can't access tty; job control turned off\n");
			mflag = 0;
			return;
		}
		if (initialpgrp == -1)
			initialpgrp = getpgrp();
		else if (initialpgrp != getpgrp())
			killpg(0, SIGTTIN);

#ifdef OLD_TTY_DRIVER
		if (ioctl(ttyfd, TIOCGETD, (char *)&ldisc) < 0
		    || ldisc != NTTYDISC) {
			out2str("sh: need new tty driver to run job control; job control turned off\n");
			mflag = 0;
			return;
		}
#endif
		setsignal(SIGTSTP, 0);
		setsignal(SIGTTOU, 0);
		setsignal(SIGTTIN, 0);
		if (getpgrp() != rootpid && setpgid(0, rootpid) == -1)
			error("Cannot set process group (%s) at %d",
			    strerror(errno), __LINE__);
		if (tcsetpgrp(ttyfd, rootpid) == -1)
			error("Cannot set tty process group (%s) at %d",
			    strerror(errno), __LINE__);
	} else { /* turning job control off */
		if (getpgrp() != initialpgrp && setpgid(0, initialpgrp) == -1)
			error("Cannot set process group (%s) at %d",
			    strerror(errno), __LINE__);
		if (tcsetpgrp(ttyfd, initialpgrp) == -1)
			error("Cannot set tty process group (%s) at %d",
			    strerror(errno), __LINE__);
		sh_close(ttyfd);
		ttyfd = -1;
		setsignal(SIGTSTP, 0);
		setsignal(SIGTTOU, 0);
		setsignal(SIGTTIN, 0);
	}
	jobctl = on;
}


#ifdef mkinit
INCLUDE <stdlib.h>

SHELLPROC {
	backgndpid = -1;
#if JOBS
	jobctl = 0;
#endif
}

#endif



#if JOBS
static int
do_fgcmd(const char *arg_ptr)
{
	struct job *jp;
	int i;
	int status;

	if (jobs_invalid)
		error("No current jobs");
	jp = getjob(arg_ptr, 0);
	if (jp->jobctl == 0)
		error("job not created under job control");
	out1fmt("%s", jp->ps[0].cmd);
	for (i = 1; i < jp->nprocs; i++)
		out1fmt(" | %s", jp->ps[i].cmd );
	out1c('\n');
	flushall();

	if (tcsetpgrp(ttyfd, jp->pgrp) == -1) {
		error("Cannot set tty process group (%s) at %d",
		    strerror(errno), __LINE__);
	}
	INTOFF;
	restartjob(jp);
	status = waitforjob(jp);
	INTON;
	return status;
}

int
fgcmd(int argc, char **argv)
{
	nextopt("");
	return do_fgcmd(*argptr);
}

int
fgcmd_percent(int argc, char **argv)
{
	nextopt("");
	return do_fgcmd(*argv);
}

static void
set_curjob(struct job *jp, int mode)
{
	struct job *jp1, *jp2;
	int i, ji;

	ji = jp - jobtab;

	/* first remove from list */
	if (ji == curjob)
		curjob = jp->prev_job;
	else {
		for (i = 0; i < njobs; i++) {
			if (jobtab[i].prev_job != ji)
				continue;
			jobtab[i].prev_job = jp->prev_job;
			break;
		}
	}

	/* Then re-insert in correct position */
	switch (mode) {
	case 0:	/* job being deleted */
		jp->prev_job = -1;
		break;
	case 1:	/* newly created job or backgrounded job,
		   put after all stopped jobs. */
		if (curjob != -1 && jobtab[curjob].state == JOBSTOPPED) {
			for (jp1 = jobtab + curjob; ; jp1 = jp2) {
				if (jp1->prev_job == -1)
					break;
				jp2 = jobtab + jp1->prev_job;
				if (jp2->state != JOBSTOPPED)
					break;
			}
			jp->prev_job = jp1->prev_job;
			jp1->prev_job = ji;
			break;
		}
		/* FALLTHROUGH */
	case 2:	/* newly stopped job - becomes curjob */
		jp->prev_job = curjob;
		curjob = ji;
		break;
	}
}

int
bgcmd(int argc, char **argv)
{
	struct job *jp;
	int i;

	nextopt("");
	if (jobs_invalid)
		error("No current jobs");
	do {
		jp = getjob(*argptr, 0);
		if (jp->jobctl == 0)
			error("job not created under job control");
		set_curjob(jp, 1);
		out1fmt("[%d] %s", JNUM(jp), jp->ps[0].cmd);
		for (i = 1; i < jp->nprocs; i++)
			out1fmt(" | %s", jp->ps[i].cmd );
		out1c('\n');
		flushall();
		restartjob(jp);
	} while (*argptr && *++argptr);
	return 0;
}


STATIC void
restartjob(struct job *jp)
{
	struct procstat *ps;
	int i, e;

	if (jp->state == JOBDONE)
		return;
	if (jp->pgrp == 0)
		error("Job [%d] does not have a process group", JNUM(jp));

	INTOFF;
	for (e = i = 0; i < jp->nprocs; i++) {
		/*
		 * Don't touch a process we already waited for and collected
		 * exit status, that pid may have been reused for something
		 * else - even another of our jobs
		 */
		if (jp->ps[i].status != -1 && !WIFSTOPPED(jp->ps[i].status))
			continue;

		/*
		 * Otherwise tell it to continue, if it worked, we're done
		 * (we signal the whole process group)
		 */
		if (killpg(jp->pgrp, SIGCONT) != -1)
			break;
		e = errno;
		break;		/* no point trying again */
	}

	if (e != 0)
		error("Cannot continue job (%s)", strerror(e));
	else if (i >= jp->nprocs)
		error("Job [%d] has no stopped processes", JNUM(jp));

	/*
	 * Now change state of all stopped processes in the job to running
	 * If there were any, the job is now running as well.
	 */
	for (ps = jp->ps, i = jp->nprocs ; --i >= 0 ; ps++) {
		if (WIFSTOPPED(ps->status)) {
			VTRACE(DBG_JOBS, (
			   "restartjob: [%d] pid %d status change"
			   " from %#x (stopped) to -1 (running)\n",
			   JNUM(jp), ps->pid, ps->status));
			ps->status = -1;
			jp->state = JOBRUNNING;
		}
	}
	INTON;
}
#endif

inline static void
cmdputi(int n)
{
	char str[20];

	fmtstr(str, sizeof str, "%d", n);
	cmdputs(str);
}

static void
showjob(struct output *out, struct job *jp, int mode)
{
	int procno;
	int st;
	struct procstat *ps;
	int col;
	char s[64];

#if JOBS
	if (mode & SHOW_PGID) {
		/* output only the process group ID (lead process ID) */
		outfmt(out, "%ld\n",
		    jp->pgrp != 0 ? (long)jp->pgrp : (long)jp->ps->pid);
		return;
	}
#endif

	procno = jp->nprocs;
	if (!procno)
		return;

	if (mode & SHOW_PID)
		mode |= SHOW_MULTILINE;

	if ((procno > 1 && !(mode & SHOW_MULTILINE))
	    || (mode & SHOW_SIGNALLED)) {
		/* See if we have more than one status to report */
		ps = jp->ps;
		st = ps->status;
		do {
			int st1 = ps->status;
			if (st1 != st)
				/* yes - need multi-line output */
				mode |= SHOW_MULTILINE;
			if (st1 == -1 || !(mode & SHOW_SIGNALLED) || WIFEXITED(st1))
				continue;
			if (WIFSTOPPED(st1) || ((st1 = WTERMSIG(st1) & 0x7f)
			    && st1 != SIGINT && st1 != SIGPIPE))
				mode |= SHOW_ISSIG;

		} while (ps++, --procno);
		procno = jp->nprocs;
	}

	if (mode & SHOW_SIGNALLED && !(mode & SHOW_ISSIG)) {
		if (jp->state == JOBDONE && !(mode & SHOW_NO_FREE)) {
			VTRACE(DBG_JOBS, ("showjob: freeing job %d\n",
			    JNUM(jp)));
			freejob(jp);
		}
		return;
	}

	for (ps = jp->ps; --procno >= 0; ps++) {	/* for each process */
		if (ps == jp->ps)
			fmtstr(s, 16, "[%d] %c ",
				JNUM(jp),
#if JOBS
				jp - jobtab == curjob ?
									  '+' :
				curjob != -1 &&
				    jp - jobtab == jobtab[curjob].prev_job ?
									  '-' :
#endif
				' ');
		else
			fmtstr(s, 16, "      " );
		col = strlen(s);
		if (mode & SHOW_PID) {
			fmtstr(s + col, 16, "%ld ", (long)ps->pid);
			     col += strlen(s + col);
		}
		if (ps->status == -1) {
			scopy("Running", s + col);
		} else if (WIFEXITED(ps->status)) {
			st = WEXITSTATUS(ps->status);
			if (st)
				fmtstr(s + col, 16, "Done(%d)", st);
			else
				fmtstr(s + col, 16, "Done");
		} else {
#if JOBS
			if (WIFSTOPPED(ps->status))
				st = WSTOPSIG(ps->status);
			else /* WIFSIGNALED(ps->status) */
#endif
				st = WTERMSIG(ps->status);
			scopyn(strsignal(st), s + col, 32);
			if (WCOREDUMP(ps->status)) {
				col += strlen(s + col);
				scopyn(" (core dumped)", s + col,  64 - col);
			}
		}
		col += strlen(s + col);
		outstr(s, out);
		do {
			outc(' ', out);
			col++;
		} while (col < 30);
		outstr(ps->cmd, out);
		if (mode & SHOW_MULTILINE) {
			if (procno > 0) {
				outc(' ', out);
				outc('|', out);
			}
		} else {
			while (--procno >= 0)
				outfmt(out, " | %s", (++ps)->cmd );
		}
		outc('\n', out);
	}
	flushout(out);
	jp->flags &= ~JOBCHANGED;
	if (jp->state == JOBDONE && !(mode & SHOW_NO_FREE))
		freejob(jp);
}

int
jobscmd(int argc, char **argv)
{
	int mode, m;

	mode = 0;
	while ((m = nextopt("lpZ")))
		switch (m) {
		case 'l':
			mode = SHOW_PID;
			break;
		case 'p':
			mode = SHOW_PGID;
			break;
		case 'Z':
			mode = SHOW_PROCTITLE;
			break;
		}

	if (mode == SHOW_PROCTITLE) {
		if (*argptr && **argptr)
			setproctitle("%s", *argptr);
		else
			setproctitle(NULL);
		return 0;
	}

	if (!iflag && !posix)
		mode |= SHOW_NO_FREE;

	if (*argptr) {
		do
			showjob(out1, getjob(*argptr,0), mode);
		while (*++argptr);
	} else
		showjobs(out1, mode);
	return 0;
}


/*
 * Print a list of jobs.  If "change" is nonzero, only print jobs whose
 * statuses have changed since the last call to showjobs.
 *
 * If the shell is interrupted in the process of creating a job, the
 * result may be a job structure containing zero processes.  Such structures
 * will be freed here.
 */

void
showjobs(struct output *out, int mode)
{
	int jobno;
	struct job *jp;
	int silent = 0, gotpid;

	CTRACE(DBG_JOBS, ("showjobs(%x) called\n", mode));

	/*  Collect everything pending in the kernel */
	if ((gotpid = dowait(WSILENT, NULL, NULL)) > 0)
		while (dowait(WSILENT, NULL, NULL) > 0)
			continue;
#ifdef JOBS
	/*
	 * Check if we are not in our foreground group, and if not
	 * put us in it.
	 */
	if (mflag && gotpid != -1 && tcgetpgrp(ttyfd) != getpid()) {
		if (tcsetpgrp(ttyfd, getpid()) == -1)
			error("Cannot set tty process group (%s) at %d",
			    strerror(errno), __LINE__);
		VTRACE(DBG_JOBS|DBG_INPUT, ("repaired tty process group\n"));
		silent = 1;
	}
#endif

	for (jobno = 1, jp = jobtab ; jobno <= njobs ; jobno++, jp++) {
		if (!jp->used)
			continue;
		if (jp->nprocs == 0) {
			if (!jobs_invalid)
				freejob(jp);
			continue;
		}
		if ((mode & SHOW_CHANGED) && !(jp->flags & JOBCHANGED))
			continue;
		if (silent && (jp->flags & JOBCHANGED)) {
			jp->flags &= ~JOBCHANGED;
			continue;
		}
		showjob(out, jp, mode);
	}
}

/*
 * Mark a job structure as unused.
 */

STATIC void
freejob(struct job *jp)
{
	INTOFF;
	if (jp->ps != &jp->ps0) {
		ckfree(jp->ps);
		jp->ps = &jp->ps0;
	}
	jp->nprocs = 0;
	jp->used = 0;
#if JOBS
	set_curjob(jp, 0);
#endif
	INTON;
}

/*
 * Extract the status of a completed job (for $?)
 */
STATIC int
jobstatus(const struct job *jp, int raw)
{
	int status = 0;
	int retval;

	if ((jp->flags & JPIPEFAIL) && jp->nprocs) {
		int i;

		for (i = 0; i < jp->nprocs; i++)
			if (jp->ps[i].status != 0)
				status = jp->ps[i].status;
	} else
		status = jp->ps[jp->nprocs ? jp->nprocs - 1 : 0].status;

	if (raw)
		return status;

	if (WIFEXITED(status))
		retval = WEXITSTATUS(status);
#if JOBS
	else if (WIFSTOPPED(status))
		retval = WSTOPSIG(status) + 128;
#endif
	else {
		/* XXX: limits number of signals */
		retval = WTERMSIG(status) + 128;
	}

	return retval;
}



int
waitcmd(int argc, char **argv)
{
	struct job *job, *last;
	int retval;
	struct job *jp;
	int i;
	int any = 0;
	int found;
	int oldwait = 0;
	char *pid = NULL, *fpid;
	char **arg;
	char idstring[20];

	while ((i = nextopt("np:")) != '\0') {
		switch (i) {
		case 'n':
			any = 1;
			break;
		case 'p':
			if (pid)
				error("more than one -p unsupported");
			pid = optionarg;
			break;
		}
	}

	if (!any && *argptr == 0)
		oldwait = 1;

	if (pid != NULL) {
		if (!validname(pid, '\0', NULL))
			error("invalid name: -p '%s'", pid);
		if (unsetvar(pid, 0))
			error("%s readonly", pid);
	}

	/*
	 * If we have forked, and not yet created any new jobs, then
	 * we have no children, whatever jobtab claims,
	 * so simply return in that case.
	 *
	 * The return code is 127 if we had any pid args (none are found)
	 * or if we had -n (nothing exited), but 0 for plain old "wait".
	 */
	if (jobs_invalid) {
		CTRACE(DBG_WAIT, ("builtin wait%s%s in child, invalid jobtab\n",
		    any ? " -n" : "", *argptr ? " pid..." : ""));
		return oldwait ? 0 : 127;
	}

	/*
	 * clear stray flags left from previous waitcmd
	 * or set them instead if anything will do ("wait -n")
	 */
	for (jp = jobtab, i = njobs ; --i >= 0 ; jp++) {
		if (any && *argptr == NULL)
			jp->flags |= JOBWANTED;
		else
			jp->flags &= ~JOBWANTED;
		jp->ref = NULL;
	}

	CTRACE(DBG_WAIT,
	    ("builtin wait%s%s\n", any ? " -n" : "", *argptr ? " pid..." : ""));

	/*
	 * First, validate the jobnum args, count how many refer to
	 * (different) running jobs, and if we had -n, and found that one has
	 * already finished, we return that one.   Otherwise remember
	 * which ones we are looking for (JOBWANTED).
	 */
	found = 0;
	last = NULL;
#ifdef	DEBUG
	job = NULL;
#endif
	for (arg = argptr; *arg; arg++) {
		last = jp = getjob(*arg, 1);
		if (!jp)
			continue;
		if (jp->ref == NULL)
			jp->ref = *arg;
		if (any && jp->state == JOBDONE) {
			/*
			 * We just want any of them, and this one is
			 * ready for consumption, bon apetit ...
			 */
			retval = jobstatus(jp, 0);
			if (pid)
				setvar(pid, *arg, 0);
			if (!iflag)
				freejob(jp);
			CTRACE(DBG_WAIT, ("wait -n found %s already done: %d\n",			    *arg, retval));
			return retval;
		}
		if (!(jp->flags & JOBWANTED)) {
			/*
			 * It is possible to list the same job several
			 * times - the obvious "wait 1 1 1" or
			 * "wait %% %2 102" where job 2 is current and pid 102
			 * However many times it is requested, it is found once.
			 */
			found++;
			jp->flags |= JOBWANTED;
		}
#ifdef DEBUG
		job = jp;
#endif
	}

	VTRACE(DBG_WAIT, ("wait %s%s%sfound %d candidates (last %s)\n",
	    any ? "-n " : "", *argptr ? *argptr : "",
	    argptr[0] && argptr[1] ? "... " : " ", found,
	    job && job->used ? (job->ref ? job->ref : "<no-arg>") : "none"));

	/*
	 * If we were given a list of jobnums:
	 * and none of those exist, then we're done.
	 */
	if (*argptr && found == 0)
		return 127;

	/*
	 * Otherwise we need to wait for something to complete
	 * When it does, we check and see if it is one of the
	 * jobs we're waiting on, and if so, we clean it up.
	 * If we had -n, then we're done, otherwise we do it all again
	 * until all we had listed are done, of if there were no
	 * jobnum args, all are done.
	 */

	retval = any || *argptr ? 127 : 0;
	fpid = NULL;
	for (;;) {
		VTRACE(DBG_WAIT, ("wait waiting (%d remain): ", found));
		job = NULL;
		for (jp = jobtab, i = njobs; --i >= 0; jp++) {
			if (jp->used && jp->flags & JOBWANTED &&
			    jp->state == JOBDONE) {
				job = jp;
				break;
			}
			if (jp->used && jp->state == JOBRUNNING)
				job = jp;
		}
		if (i < 0 && job == NULL) {
			CTRACE(DBG_WAIT, ("nothing running (ret: %d) fpid %s\n",
			    retval, fpid ? fpid : "unset"));
			if (pid && fpid)
				setvar(pid, fpid, 0);
			return retval;
		}
		jp = job;
		VTRACE(DBG_WAIT, ("found @%d/%d state: %d\n", njobs-i, njobs,
		    jp->state));

		/*
		 * There is at least 1 job running, so we can
		 * safely wait() (blocking) for something to exit.
		 */
		if (jp->state == JOBRUNNING) {
			job = NULL;
			if ((i = dowait(WBLOCK|WNOFREE, NULL, &job)) == -1)
			       return 128 + lastsig();

			/*
			 * This happens if an interloper has died
			 * (eg: a child of the executable that exec'd us)
			 * Simply go back and start all over again
			 * (this is rare).
			 */
			if (job == NULL)
				continue;

			/*
			 * one of the reported job's processes exited,
			 * but there are more still running, back for more
			 */
			if (job->state == JOBRUNNING)
				continue;
		} else
			job = jp;	/* we want this, and it is done */

		if (job->flags & JOBWANTED) {
			int rv;

			job->flags &= ~JOBWANTED;	/* got it */
			rv = jobstatus(job, 0);
			VTRACE(DBG_WAIT, (
			    "wanted %d (%s) done: st=%d", i,
			    job->ref ? job->ref : "", rv));
			if (any || job == last) {
				retval = rv;
				fpid = job->ref;

				VTRACE(DBG_WAIT, (" save"));
				if (pid) {
				   /*
				    * don't need fpid unless we are going
				    * to return it.
				    */
				   if (fpid == NULL) {
					/*
					 * this only happens with "wait -n"
					 * (that is, no pid args)
					 */
					snprintf(idstring, sizeof idstring,
					    "%d", job->ps[ job->nprocs ?
						    job->nprocs-1 : 0 ].pid);
					fpid = idstring;
				    }
				    VTRACE(DBG_WAIT, (" (for %s)", fpid));
				}
			}

			if (job->state == JOBDONE) {
				VTRACE(DBG_WAIT, (" free"));
				freejob(job);
			}

			if (any || (found > 0 && --found == 0)) {
				if (pid && fpid)
					setvar(pid, fpid, 0);
				VTRACE(DBG_WAIT, (" return %d\n", retval));
				return retval;
			}
			VTRACE(DBG_WAIT, ("\n"));
			continue;
		}

		/* this is to handle "wait" (no args) */
		if (oldwait && job->state == JOBDONE) {
			VTRACE(DBG_JOBS|DBG_WAIT, ("Cleanup: %d\n", i));
			freejob(job);
		}
	}
}


int
jobidcmd(int argc, char **argv)
{
	struct job *jp;
	int i;
	int pg = 0, onep = 0, job = 0;

	while ((i = nextopt("gjp"))) {
		switch (i) {
		case 'g':	pg = 1;		break;
		case 'j':	job = 1;	break;
		case 'p':	onep = 1;	break;
		}
	}
	CTRACE(DBG_JOBS, ("jobidcmd%s%s%s%s %s\n", pg ? " -g" : "",
	    onep ? " -p" : "", job ? " -j" : "", jobs_invalid ? " [inv]" : "",
	    *argptr ? *argptr : "<implicit %%>"));
	if (pg + onep + job > 1)
		error("-g -j and -p options cannot be combined");

	if (argptr[0] && argptr[1])
		error("usage: jobid [-g|-p|-r] jobid");

	jp = getjob(*argptr, 0);
	if (job) {
		out1fmt("%%%d\n", JNUM(jp));
		return 0;
	}
	if (pg) {
		if (jp->pgrp != 0) {
			out1fmt("%ld\n", (long)jp->pgrp);
			return 0;
		}
		return 1;
	}
	if (onep) {
		i = jp->nprocs - 1;
		if (i < 0)
			return 1;
		out1fmt("%ld\n", (long)jp->ps[i].pid);
		return 0;
	}
	for (i = 0 ; i < jp->nprocs ; ) {
		out1fmt("%ld", (long)jp->ps[i].pid);
		out1c(++i < jp->nprocs ? ' ' : '\n');
	}
	return 0;
}

#if JOBS
#ifndef SMALL

static int
stop_me(int sig, int force, int pgrp, pid_t pid)
{
	if (force || (!loginsh && mflag && rootshell)) {
		struct sigaction sig_dfl, sig_was;

		sig_dfl.sa_handler = SIG_DFL;
		sig_dfl.sa_flags = 0;
		sigemptyset(&sig_dfl.sa_mask);

		(void)sigaction(sig, &sig_dfl, &sig_was);

		if (kill(pgrp ? 0 : pid, sig) == -1) {
			sh_warn("suspend myself");
			(void)sigaction(sig, &sig_was, NULL);
			error(NULL);
		}

		(void)sigaction(sig, &sig_was, NULL);

		return 0;
	}

	if (!rootshell)
		sh_warnx("subshell environment");
	else if (!mflag)
		sh_warnx("job control disabled");
	else if (loginsh)
		sh_warnx("login shell");
	else
		sh_warnx("not possible??");

	return 1;
}

int
suspendcmd(int argc, char **argv)
{
	int sig = SIGTSTP;
	int force = 0;
	int pgrp = 0;
	int status = 0;
	char *target;
	int c;

	while ((c = nextopt("fgs:")) != 0) {
		switch (c) {
		case 'f':
			force = 1;
			break;
		case 'g':
			pgrp = 1;
			break;
		case 's':
			sig = signame_to_signum(optionarg);

			if (sig != SIGSTOP && sig != SIGTSTP &&
			    sig != SIGTTIN && sig != SIGTTOU)
				error("bad signal '%s'", optionarg);
			break;
		}
	}

	if (!*argptr)		/* suspend myself */
		return stop_me(sig, force, pgrp, getpid());

	while ((target = *argptr++) != NULL)
	{
		int pid;

		if (is_number(target)) {
			if ((pid = number(target)) == 0) {
				sh_warnx("Cannot (yet) suspend kernel (%s)",
				    target);
				status = 1;
				continue;
			}
		} else if ((pid = getjobpgrp(target)) == 0) {
			sh_warnx("Unknown job: %s", target);
			status = 1;
			continue;
		}

		if (pid == rootpid || pid == getpid()) {
			status |= stop_me(sig, force, pgrp, pid);
			continue;
		}

		if (pid == 1 || pid == -1) {
			sh_warnx("Don't be funny");
			status = 1;
			continue;
		}

		if (pid > 0 && pgrp)
			pid = -pid;

		if (kill(pid, sig) == -1) {
			sh_warn("failed to suspend %s", target);
			status = 1;
		}
	}

	return status;
}
#endif	/* SMALL */
#endif	/* JOBS */

int
getjobpgrp(const char *name)
{
	struct job *jp;

	if (jobs_invalid)
		return 0;
	jp = getjob(name, 1);
	if (jp == 0)
		return 0;
	return -jp->pgrp;
}

/*
 * Convert a job name to a job structure.
 */

STATIC struct job *
getjob(const char *name, int noerror)
{
	int jobno = -1;
	struct job *jp;
	int pid;
	int i;
	const char *err_msg = "No such job: %s";

	if (name == NULL) {
#if JOBS
		jobno = curjob;
#endif
		err_msg = "No current job";
	} else if (name[0] == '%') {
		if (is_number(name + 1)) {
			jobno = number(name + 1) - 1;
		} else if (!name[1] || !name[2]) {
			switch (name[1]) {
#if JOBS
			case 0:
			case '+':
			case '%':
				jobno = curjob;
				err_msg = "No current job";
				break;
			case '-':
				jobno = curjob;
				if (jobno != -1)
					jobno = jobtab[jobno].prev_job;
				err_msg = "No previous job";
				break;
#endif
			default:
				goto check_pattern;
			}
		} else {
			struct job *found;
    check_pattern:
			found = NULL;
			for (jp = jobtab, i = njobs ; --i >= 0 ; jp++) {
				if (!jp->used || jp->nprocs <= 0)
					continue;
				if ((name[1] == '?'
					&& strstr(jp->ps[0].cmd, name + 2))
				    || prefix(name + 1, jp->ps[0].cmd)) {
					if (found) {
						err_msg = "%s: ambiguous";
						found = 0;
						break;
					}
					found = jp;
				}
			}
			if (found)
				return found;
		}

	} else if (is_number(name)) {
		pid = number(name);
		for (jp = jobtab, i = njobs ; --i >= 0 ; jp++) {
			if (jp->used && jp->nprocs > 0
			 && jp->ps[jp->nprocs - 1].pid == pid)
				return jp;
		}
	}

	if (jobno >= 0 && jobno < njobs) {
		jp = jobtab + jobno;
		if (jp->used)
			return jp;
	}
	if (!noerror)
		error(err_msg, name);
	return 0;
}


/*
 * Find out if there are any running (that is, unwaited upon)
 * background children of the current shell.
 *
 * Return 1/0 (yes, no).
 *
 * Needed as we cannot optimise away sub-shell creation if
 * we have such a child, or a "wait" in that sub-shell would
 * observe the already existing job.
 */
int
anyjobs(void)
{
	struct job *jp;
	int i;

	if (jobs_invalid)
		return 0;

	for (i = njobs, jp = jobtab ; --i >= 0 ; jp++) {
		if (jp->used)
			return 1;
	}

	return 0;
}

/*
 * Output the (new) POSIX required "[%d] %d" string whenever an
 * async (ie: background) job is started in an interactive shell.
 * Note that a subshell environment is not regarded as interactive.
 */
void
jobstarted(struct job *jp)
{
	if (!iflag || !rootshell)
		return;

	outfmt(out2, "[%d] %ld\n", JNUM(jp),
	    jp->pgrp != 0 ? (long)jp->pgrp : (long)jp->ps->pid);
}

/*
 * Return a new job structure,
 */

struct job *
makejob(union node *node, int nprocs)
{
	int i;
	struct job *jp;

	if (jobs_invalid) {
		VTRACE(DBG_JOBS, ("makejob(%p, %d) clearing jobtab (%d)\n",
			(void *)node, nprocs, njobs));
		for (i = njobs, jp = jobtab ; --i >= 0 ; jp++) {
			if (jp->used)
				freejob(jp);
		}
		jobs_invalid = 0;
	}

	for (i = njobs, jp = jobtab ; ; jp++) {
		if (--i < 0) {
			INTOFF;
			if (njobs == 0) {
				jobtab = ckmalloc(4 * sizeof jobtab[0]);
			} else {
				jp = ckmalloc((njobs + 4) * sizeof jobtab[0]);
				memcpy(jp, jobtab, njobs * sizeof jp[0]);
				/* Relocate `ps' pointers */
				for (i = 0; i < njobs; i++)
					if (jp[i].ps == &jobtab[i].ps0)
						jp[i].ps = &jp[i].ps0;
				ckfree(jobtab);
				jobtab = jp;
			}
			jp = jobtab + njobs;
			for (i = 4 ; --i >= 0 ; njobs++) {
				jobtab[njobs].used = 0;
				jobtab[njobs].prev_job = -1;
			}
			INTON;
			break;
		}
		if (jp->used == 0)
			break;
	}
	INTOFF;
	jp->state = JOBRUNNING;
	jp->used = 1;
	jp->flags = pipefail ? JPIPEFAIL : 0;
	jp->nprocs = 0;
	jp->pgrp = 0;
#if JOBS
	jp->jobctl = jobctl;
	set_curjob(jp, 1);
#endif
	if (nprocs > 1) {
		jp->ps = ckmalloc(nprocs * sizeof (struct procstat));
	} else {
		jp->ps = &jp->ps0;
	}
	INTON;
	VTRACE(DBG_JOBS, ("makejob(%p, %d)%s returns %%%d\n", (void *)node,
	    nprocs, (jp->flags & JPIPEFAIL) ? " PF" : "", JNUM(jp)));
	return jp;
}


/*
 * Fork off a subshell.  If we are doing job control, give the subshell its
 * own process group.  Jp is a job structure that the job is to be added to.
 * N is the command that will be evaluated by the child.  Both jp and n may
 * be NULL.  The mode parameter can be one of the following:
 *	FORK_FG - Fork off a foreground process.
 *	FORK_BG - Fork off a background process.
 *	FORK_NOJOB - Like FORK_FG, but don't give the process its own
 *		     process group even if job control is on.
 *
 * When job control is turned off, background processes have their standard
 * input redirected to /dev/null (except for the second and later processes
 * in a pipeline).
 */

int
forkshell(struct job *jp, union node *n, int mode)
{
	pid_t pid;
	int serrno;

	CTRACE(DBG_JOBS, ("forkshell(%%%d, %p, %d) called\n",
	    JNUM(jp), n, mode));

	switch ((pid = fork())) {
	case -1:
		serrno = errno;
		VTRACE(DBG_JOBS, ("Fork failed, errno=%d\n", serrno));
		error("Cannot fork (%s)", strerror(serrno));
		break;
	case 0:
		SHELL_FORKED();
		forkchild(jp, n, mode, 0);
		return 0;
	default:
		return forkparent(jp, n, mode, pid);
	}
}

int
forkparent(struct job *jp, union node *n, int mode, pid_t pid)
{
	int pgrp = 0;

	if (rootshell && mode != FORK_NOJOB && mflag) {
		/*
		 * The process group ID must always be that of the
		 * first process created for the job.   If this proc
		 * is the first, that's us, otherwise the pgrp has
		 * already been determined.
		 */
		if (jp == NULL || jp->nprocs == 0)
			pgrp = pid;
		else
			pgrp = jp->pgrp;
		/* This can fail because we are doing it in the child also */
		(void)setpgid(pid, pgrp);
	}
	if (mode == FORK_BG)
		backgndpid = pid;		/* set $! */
	if (jp) {
		struct procstat *ps = &jp->ps[jp->nprocs++];
		ps->pid = pid;
		ps->status = -1;
		ps->cmd[0] = 0;
		jp->pgrp = pgrp;	/* 0 if !mflag */
		if (/* iflag && rootshell && */ n)
			commandtext(ps, n);
	}
	CTRACE(DBG_JOBS, ("In parent shell: child = %d (mode %d)\n",pid,mode));
	return pid;
}

void
forkchild(struct job *jp, union node *n, int mode, int vforked)
{
	int wasroot;
	int pgrp;
	const char *devnull = _PATH_DEVNULL;
	const char *nullerr = "Can't open %s";

	wasroot = rootshell;
	CTRACE(DBG_JOBS, ("Child shell %d %sforked from %d (mode %d)\n",
	    getpid(), vforked?"v":"", getppid(), mode));

	if (!vforked) {
		rootshell = 0;
		handler = &main_handler;
	}

	closescript(vforked);
	clear_traps(vforked);
#if JOBS
	if (!vforked)
		jobctl = 0;		/* do job control only in root shell */
	if (wasroot && mode != FORK_NOJOB && mflag) {
		if (jp == NULL || jp->nprocs == 0)
			pgrp = getpid();
		else
			pgrp = jp->ps[0].pid;
		/* This can fail because we are doing it in the parent also */
		(void)setpgid(0, pgrp);
		if (mode == FORK_FG) {
			if (tcsetpgrp(ttyfd, pgrp) == -1)
				error("Cannot set tty process group (%s) at %d",
				    strerror(errno), __LINE__);
		}
		setsignal(SIGTSTP, vforked);
		setsignal(SIGTTOU, vforked);
	} else if (mode == FORK_BG) {
		ignoresig(SIGINT, vforked);
		ignoresig(SIGQUIT, vforked);
		if ((jp == NULL || jp->nprocs == 0) &&
		    ! fd0_redirected_p ()) {
			close(0);
			if (open(devnull, O_RDONLY) != 0)
				error(nullerr, devnull);
		}
	}
#else
	if (mode == FORK_BG) {
		ignoresig(SIGINT, vforked);
		ignoresig(SIGQUIT, vforked);
		if ((jp == NULL || jp->nprocs == 0) &&
		    ! fd0_redirected_p ()) {
			close(0);
			if (open(devnull, O_RDONLY) != 0)
				error(nullerr, devnull);
		}
	}
#endif
	if (wasroot && iflag) {
		setsignal(SIGINT, vforked);
		setsignal(SIGQUIT, vforked);
		setsignal(SIGTERM, vforked);
	}

	if (!vforked)
		jobs_invalid = 1;
}

/*
 * Wait for job to finish.
 *
 * Under job control we have the problem that while a child process is
 * running interrupts generated by the user are sent to the child but not
 * to the shell.  This means that an infinite loop started by an inter-
 * active user may be hard to kill.  With job control turned off, an
 * interactive user may place an interactive program inside a loop.  If
 * the interactive program catches interrupts, the user doesn't want
 * these interrupts to also abort the loop.  The approach we take here
 * is to have the shell ignore interrupt signals while waiting for a
 * foreground process to terminate, and then send itself an interrupt
 * signal if the child process was terminated by an interrupt signal.
 * Unfortunately, some programs want to do a bit of cleanup and then
 * exit on interrupt; unless these processes terminate themselves by
 * sending a signal to themselves (instead of calling exit) they will
 * confuse this approach.
 */

int
waitforjob(struct job *jp)
{
#if JOBS
	int mypgrp = getpgrp();
#endif
	int status;
	int st;

	INTOFF;
	VTRACE(DBG_JOBS, ("waitforjob(%%%d) called\n", JNUM(jp)));
	while (jp->state == JOBRUNNING) {
		dowait(WBLOCK, jp, NULL);
	}
#if JOBS
	if (jp->jobctl) {
		if (tcsetpgrp(ttyfd, mypgrp) == -1)
			error("Cannot set tty process group (%s) at %d",
			    strerror(errno), __LINE__);
	}
	if (jp->state == JOBSTOPPED && curjob != jp - jobtab)
		set_curjob(jp, 2);
#endif
	status = jobstatus(jp, 1);

	/* convert to 8 bits */
	if (WIFEXITED(status))
		st = WEXITSTATUS(status);
#if JOBS
	else if (WIFSTOPPED(status))
		st = WSTOPSIG(status) + 128;
#endif
	else
		st = WTERMSIG(status) + 128;

	VTRACE(DBG_JOBS, ("waitforjob: job %d, nproc %d, status %d, st %x\n",
		JNUM(jp), jp->nprocs, status, st));
#if JOBS
	if (jp->jobctl) {
		/*
		 * This is truly gross.
		 * If we're doing job control, then we did a TIOCSPGRP which
		 * caused us (the shell) to no longer be in the controlling
		 * session -- so we wouldn't have seen any ^C/SIGINT.  So, we
		 * intuit from the subprocess exit status whether a SIGINT
		 * occurred, and if so interrupt ourselves.  Yuck.  - mycroft
		 */
		if (WIFSIGNALED(status) && WTERMSIG(status) == SIGINT)
			raise(SIGINT);
	}
#endif
	if (! JOBS || jp->state == JOBDONE)
		freejob(jp);
	INTON;
	return st;
}



/*
 * Wait for a process (any process) to terminate.
 *
 * If "job" is given (not NULL), then its jobcontrol status (and mflag)
 * are used to determine if we wait for stopping/continuing processes or
 * only terminating ones, and the decision whether to report to stdout
 * or not varies depending what happened, and whether the affected job
 * is the one that was requested or not.
 *
 * If "changed" is not NULL, then the job which changed because a
 * process terminated/stopped will be reported by setting *changed,
 * if there is any such job, otherwise we set *changed = NULL.
 */

STATIC int
dowait(int flags, struct job *job, struct job **changed)
{
	int pid;
	int status;
	struct procstat *sp;
	struct job *jp;
	struct job *thisjob;
	int done;
	int stopped;
	int err;

	VTRACE(DBG_JOBS|DBG_PROCS, ("dowait(%x) called for job %d%s\n",
	    flags, JNUM(job), changed ? " [report change]" : ""));

	if (changed != NULL)
		*changed = NULL;

	/*
	 * First deal with the kernel, collect info on any (one) of our
	 * children that has changed state since we last asked.
	 * (loop if we're interrupted by a signal that we aren't processing)
	 */
	do {
		err = 0;
		pid = waitproc(flags & WBLOCK, job, &status);
		if (pid == -1)
			err = errno;
		VTRACE(DBG_JOBS|DBG_PROCS,
		    ("wait returns pid %d (e:%d), status %#x (ps=%d)\n",
		    pid, err, status, pendingsigs));
	} while (pid == -1 && err == EINTR && pendingsigs == 0);

	/*
	 * if nothing exited/stopped/..., we have nothing else to do
	 */
	if (pid <= 0)
		return pid;

	/*
	 * Otherwise, try to find the process, somewhere in our job table
	 */
	INTOFF;
	thisjob = NULL;
	for (jp = jobtab ; jp < jobtab + njobs ; jp++) {
		if (jp->used) {
			/*
			 * For each job that is in use (this is one)
			 */
			done = 1;	/* assume it is finished */
			stopped = 1;	/* and has stopped */

			/*
			 * Now scan all our child processes of the job
			 */
			for (sp = jp->ps ; sp < jp->ps + jp->nprocs ; sp++) {
				if (sp->pid == -1)
					continue;
				/*
				 * If the process that changed is the one
				 * we're looking at, and it was previously
				 * running (-1) or was stopped (anything else
				 * and it must have already finished earlier,
				 * so cannot be the process that just changed)
				 * then we update its status
				 */
				if (sp->pid == pid &&
				  (sp->status==-1 || WIFSTOPPED(sp->status))) {
					VTRACE(DBG_JOBS | DBG_PROCS,
			("Job %d: changing status of proc %d from %#x to ",
					    JNUM(jp), pid, sp->status));

					/*
					 * If the process continued,
					 * then update its status to running
					 * and mark the job running as well.
					 *
					 * If it was anything but running
					 * before, flag it as a change for
					 * reporting purposes later
					 */
					if (WIFCONTINUED(status)) {
						if (sp->status != -1)
							jp->flags |= JOBCHANGED;
						sp->status = -1;
						jp->state = JOBRUNNING;
						VTRACE(DBG_JOBS|DBG_PROCS,
						    ("running\n"));
					} else {
						/* otherwise update status */
						sp->status = status;
						VTRACE(DBG_JOBS|DBG_PROCS,
						    ("%#x\n", status));
					}

					/*
					 * We now know the affected job
					 */
					thisjob = jp;
					if (changed != NULL)
						*changed = jp;
				}
				/*
				 * After any update that might have just
				 * happened, if this process is running,
				 * the job is not stopped, or if the process
				 * simply stopped (not terminated) then the
				 * job is certainly not completed (done).
				 */
				if (sp->status == -1)
					stopped = 0;
				else if (WIFSTOPPED(sp->status))
					done = 0;
			}

			/*
			 * Once we have examined all processes for the
			 * job, if we still show it as stopped, then...
			 */
			if (stopped) {		/* stopped or done */
				/*
				 * it might be stopped, or finished, decide:
				 */
				int state = done ? JOBDONE : JOBSTOPPED;

				/*
				 * If that wasn't the same as it was before
				 * then update its state, and if it just
				 * completed, make it be the current job (%%)
				 */
				if (jp->state != state) {
					VTRACE(DBG_JOBS,
				("Job %d: changing state from %d to %d\n",
					    JNUM(jp), jp->state, state));
					jp->state = state;
#if JOBS
					if (done)
						set_curjob(jp, 0);
#endif
				}
			}
		}
	}

	/*
	 * Now we have scanned all jobs.   If we found the job that
	 * the process that changed state belonged to (we occasionally
	 * fork processes without associating them with a job, when one
	 * of those finishes, we simply ignore it, the zombie has been
	 * cleaned up, which is all that matters) then we need to
	 * determine if we should say something about it to stdout
	 */

	if (thisjob &&
	    (thisjob->state != JOBRUNNING || thisjob->flags & JOBCHANGED)) {
		int mode = 0;

		if (!rootshell || !iflag)
			mode = SHOW_SIGNALLED;
		if ((job == thisjob && (flags & WNOFREE) == 0) ||
		    job != thisjob)
			mode = SHOW_SIGNALLED | SHOW_NO_FREE;
		if (mode && (flags & WSILENT) == 0)
			showjob(out2, thisjob, mode);
		else {
			VTRACE(DBG_JOBS,
			    ("Not printing status for %p [%d], "
			     "mode=%#x rootshell=%d, job=%p [%d]\n",
			    thisjob, JNUM(thisjob), mode, rootshell,
			    job, JNUM(job)));
			thisjob->flags |= JOBCHANGED;
		}
	}

	INTON;
	/*
	 * Finally tell our caller that something happened (in general all
	 * anyone tests for is <= 0 (or >0) so the actual pid value here
	 * doesn't matter much, but we know pid is >0 so we may as well
	 * give back something meaningful
	 */
	return pid;
}



/*
 * Do a wait system call.  If job control is compiled in, we accept
 * stopped processes.  If block is zero, we return a value of zero
 * rather than blocking.
 *
 * System V doesn't have a non-blocking wait system call.  It does
 * have a SIGCLD signal that is sent to a process when one of its
 * children dies.  The obvious way to use SIGCLD would be to install
 * a handler for SIGCLD which simply bumped a counter when a SIGCLD
 * was received, and have waitproc bump another counter when it got
 * the status of a process.  Waitproc would then know that a wait
 * system call would not block if the two counters were different.
 * This approach doesn't work because if a process has children that
 * have not been waited for, System V will send it a SIGCLD when it
 * installs a signal handler for SIGCLD.  What this means is that when
 * a child exits, the shell will be sent SIGCLD signals continuously
 * until is runs out of stack space, unless it does a wait call before
 * restoring the signal handler.  The code below takes advantage of
 * this (mis)feature by installing a signal handler for SIGCLD and
 * then checking to see whether it was called.  If there are any
 * children to be waited for, it will be.
 *
 * If neither SYSV nor BSD is defined, we don't implement nonblocking
 * waits at all.  In this case, the user will not be informed when
 * a background process ends until the next time she runs a real program
 * (as opposed to running a builtin command or just typing return),
 * and the jobs command may give out of date information.
 */

#ifdef SYSV
STATIC int gotsigchild;

STATIC int onsigchild() {
	gotsigchild = 1;
}
#endif


STATIC int
waitproc(int block, struct job *jp, int *status)
{
#ifdef BSD
	int flags = 0;

#if JOBS
	if (mflag || (jp != NULL && jp->jobctl))
		flags |= WUNTRACED | WCONTINUED;
#endif
	if (block == 0)
		flags |= WNOHANG;
	VTRACE(DBG_WAIT, ("waitproc: doing waitpid(flags=%#x)\n", flags));
	return waitpid(-1, status, flags);
#else
#ifdef SYSV
	int (*save)();

	if (block == 0) {
		gotsigchild = 0;
		save = signal(SIGCLD, onsigchild);
		signal(SIGCLD, save);
		if (gotsigchild == 0)
			return 0;
	}
	return wait(status);
#else
	if (block == 0)
		return 0;
	return wait(status);
#endif
#endif
}

/*
 * return 1 if there are stopped jobs, otherwise 0
 */
int job_warning = 0;
int
stoppedjobs(void)
{
	int jobno;
	struct job *jp;

	if (job_warning || jobs_invalid)
		return (0);
	for (jobno = 1, jp = jobtab; jobno <= njobs; jobno++, jp++) {
		if (jp->used == 0)
			continue;
		if (jp->state == JOBSTOPPED) {
			out2str("You have stopped jobs.\n");
			job_warning = 2;
			return (1);
		}
	}

	return (0);
}

/*
 * Return a string identifying a command (to be printed by the
 * jobs command).
 */

STATIC char *cmdnextc;
STATIC int cmdnleft;

void
commandtext(struct procstat *ps, union node *n)
{
	int len;

	cmdnextc = ps->cmd;
	if (iflag || mflag || sizeof(ps->cmd) <= 60)
		len = sizeof(ps->cmd);
	else if (sizeof ps->cmd <= 400)
		len = 50;
	else if (sizeof ps->cmd <= 800)
		len = 80;
	else
		len = sizeof(ps->cmd) / 10;
	cmdnleft = len;
	(void)cmdtxt(n, 1);
	if (cmdnleft <= 0) {
		char *p = ps->cmd + len - 4;
		p[0] = '.';
		p[1] = '.';
		p[2] = '.';
		p[3] = 0;
	} else
		*cmdnextc = '\0';

	VTRACE(DBG_JOBS,
	    ("commandtext: ps->cmd %p, end %p, left %d\n\t\"%s\"\n",
	    ps->cmd, cmdnextc, cmdnleft, ps->cmd));
}


/*
 * Generate a string describing tree node n & its descendants (recursive calls)
 *
 * Return true (non-zero) if the output is complete (ends with an operator)
 * so no ';' need be added before the following command.  Return false (zero)
 * if a ';' is needed to terminate the output if it is followed by something
 * which is not an operator.
 */
STATIC int
cmdtxt(union node *n, int top)
{
	union node *np;
	struct nodelist *lp;
	const char *p;
	int i;

	if (n == NULL || cmdnleft <= 0)
		return 1;
	switch (n->type) {
	case NSEMI:
		if (!cmdtxt(n->nbinary.ch1, 0))
			cmdputs(";");
		cmdputs(" ");
		return cmdtxt(n->nbinary.ch2, 0);
	case NAND:
		(void)cmdtxt(n->nbinary.ch1, 0);
		cmdputs(" && ");
		return cmdtxt(n->nbinary.ch2, 0);
	case NOR:
		(void) cmdtxt(n->nbinary.ch1, 0);
		cmdputs(" || ");
		return cmdtxt(n->nbinary.ch2, 0);
	case NDNOT:
		cmdputs("! ");
		/* FALLTHROUGH */
	case NNOT:
		cmdputs("! ");
		return cmdtxt(n->nnot.com, 0);
		break;
	case NPIPE:
		for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
			(void) cmdtxt(lp->n, 0);
			if (lp->next)
				cmdputs(" | ");
		}
		if (!top && n->npipe.backgnd) {
			cmdputs(" &");
			return 1;
		}
		return 0;
	case NSUBSHELL:
		cmdputs("(");
		(void) cmdtxt(n->nredir.n, 0);
		cmdputs(")");
		return 0;
	case NREDIR:
	case NBACKGND:
		return cmdtxt(n->nredir.n, top);
	case NIF:
		cmdputs("if ");
		if (!cmdtxt(n->nif.test, 0))
			cmdputs(";");
		cmdputs(" then ");
		i = cmdtxt(n->nif.ifpart, 0);
		if (n->nif.elsepart) {
			if (i == 0)
				cmdputs(";");
			cmdputs(" else ");
			i = cmdtxt(n->nif.elsepart, 0);
		}
		if (i == 0)
			cmdputs(";");
		cmdputs(" fi");
		return 0;
	case NWHILE:
		cmdputs("while ");
		goto until;
	case NUNTIL:
		cmdputs("until ");
 until:
		if (!cmdtxt(n->nbinary.ch1, 0))
			cmdputs(";");
		cmdputs(" do ");
		if (!cmdtxt(n->nbinary.ch2, 0))
			cmdputs(";");
		cmdputs(" done");
		return 0;
	case NFOR:
		cmdputs("for ");
		cmdputs(n->nfor.var);
		cmdputs(" in ");
		cmdlist(n->nfor.args, 1);
		cmdputs("; do ");
		if (!cmdtxt(n->nfor.body, 0))
			cmdputs(";");
		cmdputs(" done");
		return 0;
	case NCASE:
		cmdputs("case ");
		cmdputs(n->ncase.expr->narg.text);
		cmdputs(" in ");
		for (np = n->ncase.cases; np; np = np->nclist.next) {
			(void) cmdtxt(np->nclist.pattern, 0);
			cmdputs(") ");
			(void) cmdtxt(np->nclist.body, 0);
			switch (n->type) {	/* switch (not if) for later */
			case NCLISTCONT:
				cmdputs(" ;& ");
				break;
			default:
				cmdputs(" ;; ");
				break;
			}
		}
		cmdputs("esac");
		return 0;
	case NDEFUN:
		cmdputs(n->narg.text);
		cmdputs("() { ... }");
		return 0;
	case NCMD:
		cmdlist(n->ncmd.args, 1);
		cmdlist(n->ncmd.redirect, 0);
		if (!top && n->ncmd.backgnd) {
			cmdputs(" &");
			return 1;
		}
		return 0;
	case NARG:
		cmdputs(n->narg.text);
		return 0;
	case NTO:
		p = ">";  i = 1;  goto redir;
	case NCLOBBER:
		p = ">|";  i = 1;  goto redir;
	case NAPPEND:
		p = ">>";  i = 1;  goto redir;
	case NTOFD:
		p = ">&";  i = 1;  goto redir;
	case NFROM:
		p = "<";  i = 0;  goto redir;
	case NFROMFD:
		p = "<&";  i = 0;  goto redir;
	case NFROMTO:
		p = "<>";  i = 0;  goto redir;
 redir:
		if (n->nfile.fd != i)
			cmdputi(n->nfile.fd);
		cmdputs(p);
		if (n->type == NTOFD || n->type == NFROMFD) {
			if (n->ndup.dupfd < 0)
				cmdputs("-");
			else
				cmdputi(n->ndup.dupfd);
		} else {
			(void) cmdtxt(n->nfile.fname, 0);
		}
		return 0;
	case NHERE:
	case NXHERE:
		cmdputs("<<...");
		return 0;
	default:
		cmdputs("???");
		return 0;
	}
	return 0;
}

STATIC void
cmdlist(union node *np, int sep)
{
	for (; np; np = np->narg.next) {
		if (!sep)
			cmdputs(" ");
		(void) cmdtxt(np, 0);
		if (sep && np->narg.next)
			cmdputs(" ");
	}
}


STATIC void
cmdputs(const char *s)
{
	const char *p, *str = 0;
	char c, cc[2] = " ";
	char *nextc;
	int nleft;
	int subtype = 0;
	int quoted = 0;
	static char vstype[16][4] = { "", "}", "-", "+", "?", "=",
					"#", "##", "%", "%%", "}" };

	p = s;
	nextc = cmdnextc;
	nleft = cmdnleft;
	while (nleft > 0 && (c = *p++) != 0) {
		switch (c) {
		case CTLNONL:
			c = '\0';
			break;
		case CTLESC:
			c = *p++;
			break;
		case CTLVAR:
			subtype = *p++;
			if (subtype & VSLINENO) {	/* undo LINENO hack */
				if ((subtype & VSTYPE) == VSLENGTH)
					str = "${#LINENO";	/*}*/
				else
					str = "${LINENO";	/*}*/
				while (is_digit(*p))
					p++;
			} else if ((subtype & VSTYPE) == VSLENGTH)
				str = "${#"; /*}*/
			else
				str = "${"; /*}*/
			if (!(subtype & VSQUOTE) != !(quoted & 1)) {
				quoted ^= 1;
				c = '"';
			} else {
				c = *str++;
			}
			break;
		case CTLENDVAR:		/*{*/
			c = '}';
			if (quoted & 1)
				str = "\"";
			quoted >>= 1;
			subtype = 0;
			break;
		case CTLBACKQ:
			c = '$';
			str = "(...)";
			break;
		case CTLBACKQ+CTLQUOTE:
			c = '"';
			str = "$(...)\"";
			break;
		case CTLARI:
			c = '$';
			if (*p == ' ')
				p++;
			str = "((";	/*))*/
			break;
		case CTLENDARI:		/*((*/
			c = ')';
			str = ")";
			break;
		case CTLQUOTEMARK:
			quoted ^= 1;
			c = '"';
			break;
		case CTLQUOTEEND:
			quoted >>= 1;
			c = '"';
			break;
		case '=':
			if (subtype == 0)
				break;
			str = vstype[subtype & VSTYPE];
			if (subtype & VSNUL)
				c = ':';
			else
				c = *str++;		/*{*/
			if (c != '}')
				quoted <<= 1;
			else if (*p == CTLENDVAR)
				c = *str++;
			subtype = 0;
			break;
		case '\'':
		case '\\':
		case '"':
		case '$':
			/* These can only happen inside quotes */
			cc[0] = c;
			str = cc;
			c = '\\';
			break;
		default:
			break;
		}
		if (c != '\0') do {	/* c == 0 implies nothing in str */
			*nextc++ = c;
		} while (--nleft > 0 && str && (c = *str++));
		str = 0;
	}
	if ((quoted & 1) && nleft) {
		*nextc++ = '"';
		nleft--;
	}
	cmdnleft = nleft;
	cmdnextc = nextc;
}