text: /*-
   * Copyright (c) 1991 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. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. 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.
   */
  
  #ifndef lint
  static char sccsid[] = "@(#)jobs.c	5.1 (Berkeley) 3/7/91";
  #endif /* not lint */
  
  #include "shell.h"
  #if JOBS
  #include "sgtty.h"
  #undef CEOF			/* syntax.h redefines this */
  #endif
  #include "main.h"
  #include "parser.h"
  #include "nodes.h"
  #include "jobs.h"
  #include "options.h"
  #include "trap.h"
  #include "signames.h"
  #include "syntax.h"
  #include "input.h"
  #include "output.h"
  #include "memalloc.h"
  #include "error.h"
  #include "mystring.h"
  #include "redir.h"
  #include <sys/types.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <errno.h>
  #ifdef BSD
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <sys/time.h>
  #include <sys/resource.h>
  #endif
  #if POSIX
  #include <sys/wait.h>
  #endif
  
  
  
  struct job *jobtab;		/* array of jobs */
  int njobs;			/* size of array */
  MKINIT short backgndpid = -1;	/* pid of last background process */
  #if JOBS
  int initialpgrp;		/* pgrp of shell on invocation */
  short curjob;			/* current job */
  #endif
  
  #ifdef __STDC__
  STATIC void restartjob(struct job *);
  STATIC struct job *getjob(char *);
  STATIC void freejob(struct job *);
  STATIC int procrunning(int);
  STATIC int dowait(int, struct job *);
  STATIC int waitproc(int, int *);
  STATIC char *commandtext(union node *);
  #else
  STATIC void restartjob();
  STATIC struct job *getjob();
  STATIC void freejob();
  STATIC int procrunning();
  STATIC int dowait();
  STATIC int waitproc();
  STATIC char *commandtext();
  #endif
  
  
   
  #if JOBS
  /*
   * 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(on) {
  	int ldisc;
  
  	if (on == jobctl || rootshell == 0)
  		return;
  	if (on) {
  		do { /* while we are in the background */
  			if (ioctl(2, TIOCGPGRP, (char *)&initialpgrp) < 0) {
  				out2str("ash: can't access tty; job control turned off\n");
  				jflag = 0;
  				return;
  			}
  			if (initialpgrp == -1)
  				initialpgrp = getpgrp(0);
  			else if (initialpgrp != getpgrp(0)) {
  				killpg(initialpgrp, SIGTTIN);
  				continue;
  			}
  		} while (0);
  		if (ioctl(2, TIOCGETD, (char *)&ldisc) < 0 || ldisc != NTTYDISC) {
  			out2str("ash: need new tty driver to run job control; job control turned off\n");
  			jflag = 0;
  			return;
  		}
  		setsignal(SIGTSTP);
  		setsignal(SIGTTOU);
  		setpgrp(0, rootpid);
  		ioctl(2, TIOCSPGRP, (char *)&rootpid);
  	} else { /* turning job control off */
  		setpgrp(0, initialpgrp);
  		ioctl(2, TIOCSPGRP, (char *)&initialpgrp);
  		setsignal(SIGTSTP);
  		setsignal(SIGTTOU);
  	}
  	jobctl = on;
  }
  #endif
  
  
  #ifdef mkinit
  
  SHELLPROC {
  	backgndpid = -1;
  #if JOBS
  	jobctl = 0;
  #endif
  }
  
  #endif
  
  
  
  #if JOBS
  fgcmd(argc, argv)  char **argv; {
  	struct job *jp;
  	int pgrp;
  	int status;
  
  	jp = getjob(argv[1]);
  	if (jp->jobctl == 0)
  		error("job not created under job control");
  	pgrp = jp->ps[0].pid;
  	ioctl(2, TIOCSPGRP, (char *)&pgrp);
  	restartjob(jp);
  	INTOFF;
  	status = waitforjob(jp);
  	INTON;
  	return status;
  }
  
  
  bgcmd(argc, argv)  char **argv; {
  	struct job *jp;
  
  	do {
  		jp = getjob(*++argv);
  		if (jp->jobctl == 0)
  			error("job not created under job control");
  		restartjob(jp);
  	} while (--argc > 1);
  	return 0;
  }
  
  
  STATIC void
  restartjob(jp)
  	struct job *jp;
  	{
  	struct procstat *ps;
  	int i;
  
  	if (jp->state == JOBDONE)
  		return;
  	INTOFF;
  	killpg(jp->ps[0].pid, SIGCONT);
  	for (ps = jp->ps, i = jp->nprocs ; --i >= 0 ; ps++) {
  		if ((ps->status & 0377) == 0177) {
  			ps->status = -1;
  			jp->state = 0;
  		}
  	}
  	INTON;
  }
  #endif
  
  
  int
  jobscmd(argc, argv)  char **argv; {
  	showjobs(0);
  	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(change) {
  	int jobno;
  	int procno;
  	int i;
  	struct job *jp;
  	struct procstat *ps;
  	int col;
  	char s[64];
  
  	TRACE(("showjobs(%d) called\n", change));
  	while (dowait(0, (struct job *)NULL) > 0);
  	for (jobno = 1, jp = jobtab ; jobno <= njobs ; jobno++, jp++) {
  		if (! jp->used)
  			continue;
  		if (jp->nprocs == 0) {
  			freejob(jp);
  			continue;
  		}
  		if (change && ! jp->changed)
  			continue;
  		procno = jp->nprocs;
  		for (ps = jp->ps ; ; ps++) {	/* for each process */
  			if (ps == jp->ps)
  				fmtstr(s, 64, "[%d] %d ", jobno, ps->pid);
  			else
  				fmtstr(s, 64, "    %d ", ps->pid);
  			out1str(s);
  			col = strlen(s);
  			s[0] = '\0';
  			if (ps->status == -1) {
  				/* don't print anything */
  			} else if ((ps->status & 0xFF) == 0) {
  				fmtstr(s, 64, "Exit %d", ps->status >> 8);
  			} else {
  				i = ps->status;
  #if JOBS
  				if ((i & 0xFF) == 0177)
  					i >>= 8;
  #endif
  				if ((i & 0x7F) <= MAXSIG && sigmesg[i & 0x7F])
  					scopy(sigmesg[i & 0x7F], s);
  				else
  					fmtstr(s, 64, "Signal %d", i & 0x7F);
  				if (i & 0x80)
  					strcat(s, " (core dumped)");
  			}
  			out1str(s);
  			col += strlen(s);
  			do {
  				out1c(' ');
  				col++;
  			} while (col < 30);
  			out1str(ps->cmd);
  			out1c('\n');
  			if (--procno <= 0)
  				break;
  		}
  		jp->changed = 0;
  		if (jp->state == JOBDONE) {
  			freejob(jp);
  		}
  	}
  }
  
  
  /*
   * Mark a job structure as unused.
   */
  
  STATIC void
  freejob(jp)
  	struct job *jp;
  	{
  	struct procstat *ps;
  	int i;
  
  	INTOFF;
  	for (i = jp->nprocs, ps = jp->ps ; --i >= 0 ; ps++) {
  		if (ps->cmd != nullstr)
  			ckfree(ps->cmd);
  	}
  	if (jp->ps != &jp->ps0)
  		ckfree(jp->ps);
  	jp->used = 0;
  #if JOBS
  	if (curjob == jp - jobtab + 1)
  		curjob = 0;
  #endif
  	INTON;
  }
  
  
  
  int
  waitcmd(argc, argv)  char **argv; {
  	struct job *job;
  	int status;
  	struct job *jp;
  
  	if (argc > 1) {
  		job = getjob(argv[1]);
  	} else {
  		job = NULL;
  	}
  	for (;;) {	/* loop until process terminated or stopped */
  		if (job != NULL) {
  			if (job->state) {
  				status = job->ps[job->nprocs - 1].status;
  				if ((status & 0xFF) == 0)
  					status = status >> 8 & 0xFF;
  #if JOBS
  				else if ((status & 0xFF) == 0177)
  					status = (status >> 8 & 0x7F) + 128;
  #endif
  				else
  					status = (status & 0x7F) + 128;
  				if (! iflag)
  					freejob(job);
  				return status;
  			}
  		} else {
  			for (jp = jobtab ; ; jp++) {
  				if (jp >= jobtab + njobs) {	/* no running procs */
  					return 0;
  				}
  				if (jp->used && jp->state == 0)
  					break;
  			}
  		}
  		dowait(1, (struct job *)NULL);
  	}
  }
  
  
  
  jobidcmd(argc, argv)  char **argv; {
  	struct job *jp;
  	int i;
  
  	jp = getjob(argv[1]);
  	for (i = 0 ; i < jp->nprocs ; ) {
  		out1fmt("%d", jp->ps[i].pid);
  		out1c(++i < jp->nprocs? ' ' : '\n');
  	}
  	return 0;
  }
  
  
  
  /*
   * Convert a job name to a job structure.
   */
  
  STATIC struct job *
  getjob(name)
  	char *name;
  	{
  	int jobno;
  	register struct job *jp;
  	int pid;
  	int i;
  
  	if (name == NULL) {
  #if JOBS
  currentjob:
  		if ((jobno = curjob) == 0 || jobtab[jobno - 1].used == 0)
  			error("No current job");
  		return &jobtab[jobno - 1];
  #else
  		error("No current job");
  #endif
  	} else if (name[0] == '%') {
  		if (is_digit(name[1])) {
  			jobno = number(name + 1);
  			if (jobno > 0 && jobno <= njobs
  			 && jobtab[jobno - 1].used != 0)
  				return &jobtab[jobno - 1];
  #if JOBS
  		} else if (name[1] == '%' && name[2] == '\0') {
  			goto currentjob;
  #endif
  		} else {
  			register struct job *found = NULL;
  			for (jp = jobtab, i = njobs ; --i >= 0 ; jp++) {
  				if (jp->used && jp->nprocs > 0
  				 && prefix(name + 1, jp->ps[0].cmd)) {
  					if (found)
  						error("%s: ambiguous", name);
  					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;
  		}
  	}
  	error("No such job: %s", name);
  }
  
  
  
  /*
   * Return a new job structure,
   */
  
  struct job *
  makejob(node, nprocs)
  	union node *node;
  	{
  	int i;
  	struct job *jp;
  
  	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]);
  				bcopy(jobtab, jp, njobs * sizeof jp[0]);
  				for (i= 0; i<njobs; i++)
  				{
  					if (jobtab[i].ps == &jobtab[i].ps0)
  						jp[i].ps= &jp[i].ps0;
  				}
  				ckfree(jobtab);
  				jobtab = jp;
  			}
  			jp = jobtab + njobs;
  			for (i = 4 ; --i >= 0 ; jobtab[njobs++].used = 0);
  			INTON;
  			break;
  		}
  		if (jp->used == 0)
  			break;
  	}
  	INTOFF;
  	jp->state = 0;
  	jp->used = 1;
  	jp->changed = 0;
  	jp->nprocs = 0;
  #if JOBS
  	jp->jobctl = jobctl;
  #endif
  	if (nprocs > 1) {
  		jp->ps = ckmalloc(nprocs * sizeof (struct procstat));
  	} else {
  		jp->ps = &jp->ps0;
  	}
  	INTON;
  	TRACE(("makejob(0x%x, %d) returns %%%d\n", (int)node, nprocs, jp - jobtab + 1));
  	return jp;
  }	
  
  
  /*
   * Fork of 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(jp, n, mode)
  	union node *n;
  	struct job *jp;
  	{
  	int pid;
  	int pgrp;
  
  	TRACE(("forkshell(%%%d, 0x%x, %d) called\n", jp - jobtab, (int)n, mode));
  	INTOFF;
  	pid = fork();
  	if (pid == -1) {
  		TRACE(("Fork failed, errno=%d\n", errno));
  		INTON;
  		error("Cannot fork");
  	}
  	if (pid == 0) {
  		struct job *p;
  		int wasroot;
  		int i;
  
  		TRACE(("Child shell %d\n", getpid()));
  		wasroot = rootshell;
  		rootshell = 0;
  		for (i = njobs, p = jobtab ; --i >= 0 ; p++)
  			if (p->used)
  				freejob(p);
  		closescript();
  		INTON;
  		clear_traps();
  #if JOBS
  		jobctl = 0;		/* do job control only in root shell */
  		if (wasroot && mode != FORK_NOJOB && jflag) {
  			if (jp == NULL || jp->nprocs == 0)
  				pgrp = getpid();
  			else
  				pgrp = jp->ps[0].pid;
  			setpgrp(0, pgrp);
  			if (mode == FORK_FG) {
  				/*** this causes superfluous TIOCSPGRPS ***/
  				if (ioctl(2, TIOCSPGRP, (char *)&pgrp) < 0)
  					error("TIOCSPGRP failed, errno=%d\n", errno);
  			}
  			setsignal(SIGTSTP);
  			setsignal(SIGTTOU);
  		} else if (mode == FORK_BG) {
  			ignoresig(SIGINT);
  			ignoresig(SIGQUIT);
  			if ((jp == NULL || jp->nprocs == 0)
  			    && ! fd0_redirected_p ()) {
  				close(0);
  				if (open("/dev/null", O_RDONLY) != 0)
  					error("Can't open /dev/null");
  			}
  		}
  #else
  		if (mode == FORK_BG) {
  			ignoresig(SIGINT);
  			ignoresig(SIGQUIT);
  			if ((jp == NULL || jp->nprocs == 0)
  			    && ! fd0_redirected_p ()) {
  				close(0);
  				if (open("/dev/null", O_RDONLY) != 0)
  					error("Can't open /dev/null");
  			}
  		}
  #endif
  		if (wasroot && iflag) {
  			setsignal(SIGINT);
  			setsignal(SIGQUIT);
  			setsignal(SIGTERM);
  		}
  		return pid;
  	}
  	if (rootshell && mode != FORK_NOJOB && jflag) {
  		if (jp == NULL || jp->nprocs == 0)
  			pgrp = pid;
  		else
  			pgrp = jp->ps[0].pid;
  #if JOBS
  		setpgrp(pid, pgrp);
  #endif
  	}
  	if (mode == FORK_BG)
  		backgndpid = pid;		/* set $! */
  	if (jp) {
  		struct procstat *ps = &jp->ps[jp->nprocs++];
  		ps->pid = pid;
  		ps->status = -1;
  		ps->cmd = nullstr;
  		if (iflag && rootshell && n)
  			ps->cmd = commandtext(n);
  	}
  	INTON;
  	TRACE(("In parent shell:  child = %d\n", pid));
  	return pid;
  }
  
  
  
  /*
   * 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
   * forground 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(jp)
  	register struct job *jp;
  	{
  #if JOBS
  	int mypgrp = getpgrp(0);
  #endif
  	int status;
  	int st;
  
  	INTOFF;
  	TRACE(("waitforjob(%%%d) called\n", jp - jobtab + 1));
  	while (jp->state == 0 && dowait(1, jp) != -1) ;
  #if JOBS
  	if (jp->jobctl) {
  		if (ioctl(2, TIOCSPGRP, (char *)&mypgrp) < 0)
  			error("TIOCSPGRP failed, errno=%d\n", errno);
  	}
  	if (jp->state == JOBSTOPPED)
  		curjob = jp - jobtab + 1;
  #endif
  	status = jp->ps[jp->nprocs - 1].status;
  	/* convert to 8 bits */
  	if ((status & 0xFF) == 0)
  		st = status >> 8 & 0xFF;
  #if JOBS
  	else if ((status & 0xFF) == 0177)
  		st = (status >> 8 & 0x7F) + 128;
  #endif
  	else
  		st = (status & 0x7F) + 128;
  	if (! JOBS || jp->state == JOBDONE)
  		freejob(jp);
  	CLEAR_PENDING_INT;
  	if ((status & 0x7F) == SIGINT)
  		kill(getpid(), SIGINT);
  	INTON;
  	return st;
  }
  
  
  
  /*
   * Wait for a process to terminate.
   */
  
  STATIC int
  dowait(block, job)
  	struct job *job;
  	{
  	int pid;
  	int status;
  	struct procstat *sp;
  	struct job *jp;
  	struct job *thisjob;
  	int done;
  	int stopped;
  	int core;
  
  	TRACE(("dowait(%d) called\n", block));
  	do {
  		pid = waitproc(block, &status);
  		TRACE(("wait returns %d, status=%d, errno=%d\n",
  				pid, status, errno));
  	} while (pid == -1 && errno == EINTR);
  	if (pid <= 0)
  		return pid;
  	INTOFF;
  	thisjob = NULL;
  	for (jp = jobtab ; jp < jobtab + njobs ; jp++) {
  		if (jp->used) {
  			done = 1;
  			stopped = 1;
  			for (sp = jp->ps ; sp < jp->ps + jp->nprocs ; sp++) {
  				if (sp->pid == -1)
  					continue;
  				if (sp->pid == pid) {
  					TRACE(("Changin status of proc %d from 0x%x to 0x%x\n", pid, sp->status, status));
  					sp->status = status;
  					thisjob = jp;
  				}
  				if (sp->status == -1)
  					stopped = 0;
  				else if ((sp->status & 0377) == 0177)
  					done = 0;
  			}
  			if (stopped) {		/* stopped or done */
  				int state = done? JOBDONE : JOBSTOPPED;
  				if (jp->state != state) {
  					TRACE(("Job %d: changing state from %d to %d\n", jp - jobtab + 1, jp->state, state));
  					jp->state = state;
  #if JOBS
  					if (done && curjob == jp - jobtab + 1)
  						curjob = 0;		/* no current job */
  #endif
  				}
  			}
  		}
  	}
  	INTON;
  	if (! rootshell || ! iflag || (job && thisjob == job)) {
  #if JOBS
  		if ((status & 0xFF) == 0177)
  			status >>= 8;
  #endif
  		core = status & 0x80;
  		status &= 0x7F;
  		if (status != 0 && status != SIGINT && status != SIGPIPE) {
  			if (thisjob != job)
  				outfmt(out2, "%d: ", pid);
  #if JOBS
  			if (status == SIGTSTP && rootshell && iflag)
  				outfmt(out2, "%%%d ", job - jobtab + 1);
  #endif
  			if (status <= MAXSIG && sigmesg[status])
  				out2str(sigmesg[status]);
  			else
  				outfmt(out2, "Signal %d", status);
  			if (core)
  				out2str(" - core dumped");
  			out2c('\n');
  			flushout(&errout);
  		} else {
  			TRACE(("Not printing status: status=%d\n", status));
  		}
  	} else {
  		TRACE(("Not printing status, rootshell=%d, job=0x%x\n", rootshell, job));
  		if (thisjob)
  			thisjob->changed = 1;
  	}
  	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 it's
   * 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 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(block, status)
  	int *status;
  	{
  #ifdef BSD
  	int flags;
  
  #if JOBS
  	flags = WUNTRACED;
  #else
  	flags = 0;
  #endif
  	if (block == 0)
  		flags |= WNOHANG;
  	return wait3((union wait *)status, flags, (struct rusage *)NULL);
  #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 POSIX
  	return waitpid(-1, status, block == 0 ? WNOHANG : 0);
  #else
  	if (block == 0)
  		return 0;
  	return wait(status);
  #endif
  #endif
  #endif
  }
  
  
  
  /*
   * Return a string identifying a command (to be printed by the
   * jobs command.
   */
  
  STATIC char *cmdnextc;
  STATIC int cmdnleft;
  STATIC void cmdtxt(), cmdputs();
  
  STATIC char *
  commandtext(n)
  	union node *n;
  	{
  	char *name;
  
  	cmdnextc = name = ckmalloc(50);
  	cmdnleft = 50 - 4;
  	cmdtxt(n);
  	*cmdnextc = '\0';
  	return name;
  }
  
  
  STATIC void
  cmdtxt(n)
  	union node *n;
  	{
  	union node *np;
  	struct nodelist *lp;
  	char *p;
  	int i;
  	char s[2];
  
  	if (n == NULL) return;
  
  	switch (n->type) {
  	case NSEMI:
  		cmdtxt(n->nbinary.ch1);
  		cmdputs("; ");
  		cmdtxt(n->nbinary.ch2);
  		break;
  	case NAND:
  		cmdtxt(n->nbinary.ch1);
  		cmdputs(" && ");
  		cmdtxt(n->nbinary.ch2);
  		break;
  	case NOR:
  		cmdtxt(n->nbinary.ch1);
  		cmdputs(" || ");
  		cmdtxt(n->nbinary.ch2);
  		break;
  	case NPIPE:
  		for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
  			cmdtxt(lp->n);
  			if (lp->next)
  				cmdputs(" | ");
  		}
  		break;
  	case NSUBSHELL:
  		cmdputs("(");
  		cmdtxt(n->nredir.n);
  		cmdputs(")");
  		break;
  	case NREDIR:
  	case NBACKGND:
  		cmdtxt(n->nredir.n);
  		break;
  	case NIF:
  		cmdputs("if ");
  		cmdtxt(n->nif.test);
  		cmdputs("; then ");
  		cmdtxt(n->nif.ifpart);
  		cmdputs("...");
  		break;
  	case NWHILE:
  		cmdputs("while ");
  		goto until;
  	case NUNTIL:
  		cmdputs("until ");
  until:
  		cmdtxt(n->nbinary.ch1);
  		cmdputs("; do ");
  		cmdtxt(n->nbinary.ch2);
  		cmdputs("; done");
  		break;
  	case NFOR:
  		cmdputs("for ");
  		cmdputs(n->nfor.var);
  		cmdputs(" in ...");
  		break;
  	case NCASE:
  		cmdputs("case ");
  		cmdputs(n->ncase.expr->narg.text);
  		cmdputs(" in ...");
  		break;
  	case NDEFUN:
  		cmdputs(n->narg.text);
  		cmdputs("() ...");
  		break;
  	case NCMD:
  		for (np = n->ncmd.args ; np ; np = np->narg.next) {
  			cmdtxt(np);
  			if (np->narg.next)
  				cmdputs(" ");
  		}
  		for (np = n->ncmd.redirect ; np ; np = np->nfile.next) {
  			cmdputs(" ");
  			cmdtxt(np);
  		}
  		break;
  	case NARG:
  		cmdputs(n->narg.text);
  		break;
  	case NTO:
  		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;
  redir:
  		if (n->nfile.fd != i) {
  			s[0] = n->nfile.fd + '0';
  			s[1] = '\0';
  			cmdputs(s);
  		}
  		cmdputs(p);
  		if (n->type == NTOFD || n->type == NFROMFD) {
  			s[0] = n->ndup.dupfd + '0';
  			s[1] = '\0';
  			cmdputs(s);
  		} else {
  			cmdtxt(n->nfile.fname);
  		}
  		break;
  	case NHERE:
  	case NXHERE:
  		cmdputs("<<...");
  		break;
  	default:
  		cmdputs("???");
  		break;
  	}
  }
  
  
  
  STATIC void
  cmdputs(s)
  	char *s;
  	{
  	register char *p, *q;
  	register char c;
  	int subtype = 0;
  
  	if (cmdnleft <= 0)
  		return;
  	p = s;
  	q = cmdnextc;
  	while ((c = *p++) != '\0') {
  		if (c == CTLESC)
  			*q++ = *p++;
  		else if (c == CTLVAR) {
  			*q++ = '$';
  			if (--cmdnleft > 0)
  				*q++ = '{';
  			subtype = *p++;
  		} else if (c == '=' && subtype != 0) {
  			*q++ = "}-+?="[(subtype & VSTYPE) - VSNORMAL];
  			subtype = 0;
  		} else if (c == CTLENDVAR) {
  			*q++ = '}';
  		} else if (c == CTLBACKQ | c == CTLBACKQ+CTLQUOTE)
  			cmdnleft++;		/* ignore it */
  		else
  			*q++ = c;
  		if (--cmdnleft <= 0) {
  			*q++ = '.';
  			*q++ = '.';
  			*q++ = '.';
  			break;
  		}
  	}
  	cmdnextc = q;
  }
  