text: /*-
   * Copyright (c) 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.
   * 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
  #if 0
  static char sccsid[] = "@(#)eval.c	8.9 (Berkeley) 6/8/95";
  #endif
  #endif /* not lint */
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: releng/11.0/bin/sh/eval.c 293635 2016-01-10 16:31:28Z jilles $");
  
  #include <paths.h>
  #include <signal.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sys/resource.h>
  #include <sys/wait.h> /* For WIFSIGNALED(status) */
  #include <errno.h>
  
  /*
   * Evaluate a command.
   */
  
  #include "shell.h"
  #include "nodes.h"
  #include "syntax.h"
  #include "expand.h"
  #include "parser.h"
  #include "jobs.h"
  #include "eval.h"
  #include "builtins.h"
  #include "options.h"
  #include "exec.h"
  #include "redir.h"
  #include "input.h"
  #include "output.h"
  #include "trap.h"
  #include "var.h"
  #include "memalloc.h"
  #include "error.h"
  #include "show.h"
  #include "mystring.h"
  #ifndef NO_HISTORY
  #include "myhistedit.h"
  #endif
  
  
  int evalskip;			/* set if we are skipping commands */
  int skipcount;			/* number of levels to skip */
  static int loopnest;		/* current loop nesting level */
  int funcnest;			/* depth of function calls */
  static int builtin_flags;	/* evalcommand flags for builtins */
  
  
  char *commandname;
  struct arglist *cmdenviron;
  int exitstatus;			/* exit status of last command */
  int oexitstatus;		/* saved exit status */
  
  
  static void evalloop(union node *, int);
  static void evalfor(union node *, int);
  static union node *evalcase(union node *);
  static void evalsubshell(union node *, int);
  static void evalredir(union node *, int);
  static void exphere(union node *, struct arglist *);
  static void expredir(union node *);
  static void evalpipe(union node *);
  static int is_valid_fast_cmdsubst(union node *n);
  static void evalcommand(union node *, int, struct backcmd *);
  static void prehash(union node *);
  
  
  /*
   * Called to reset things after an exception.
   */
  
  void
  reseteval(void)
  {
  	evalskip = 0;
  	loopnest = 0;
  }
  
  
  /*
   * The eval command.
   */
  
  int
  evalcmd(int argc, char **argv)
  {
          char *p;
          char *concat;
          char **ap;
  
          if (argc > 1) {
                  p = argv[1];
                  if (argc > 2) {
                          STARTSTACKSTR(concat);
                          ap = argv + 2;
                          for (;;) {
                                  STPUTS(p, concat);
                                  if ((p = *ap++) == NULL)
                                          break;
                                  STPUTC(' ', concat);
                          }
                          STPUTC('\0', concat);
                          p = grabstackstr(concat);
                  }
                  evalstring(p, builtin_flags);
          } else
                  exitstatus = 0;
          return exitstatus;
  }
  
  
  /*
   * Execute a command or commands contained in a string.
   */
  
  void
  evalstring(const char *s, int flags)
  {
  	union node *n;
  	struct stackmark smark;
  	int flags_exit;
  	int any;
  
  	flags_exit = flags & EV_EXIT;
  	flags &= ~EV_EXIT;
  	any = 0;
  	setstackmark(&smark);
  	setinputstring(s, 1);
  	while ((n = parsecmd(0)) != NEOF) {
  		if (n != NULL && !nflag) {
  			if (flags_exit && preadateof())
  				evaltree(n, flags | EV_EXIT);
  			else
  				evaltree(n, flags);
  			any = 1;
  			if (evalskip)
  				break;
  		}
  		popstackmark(&smark);
  		setstackmark(&smark);
  	}
  	popfile();
  	popstackmark(&smark);
  	if (!any)
  		exitstatus = 0;
  	if (flags_exit)
  		exraise(EXEXIT);
  }
  
  
  /*
   * Evaluate a parse tree.  The value is left in the global variable
   * exitstatus.
   */
  
  void
  evaltree(union node *n, int flags)
  {
  	int do_etest;
  	union node *next;
  	struct stackmark smark;
  
  	setstackmark(&smark);
  	do_etest = 0;
  	if (n == NULL) {
  		TRACE(("evaltree(NULL) called\n"));
  		exitstatus = 0;
  		goto out;
  	}
  	do {
  		next = NULL;
  #ifndef NO_HISTORY
  		displayhist = 1;	/* show history substitutions done with fc */
  #endif
  		TRACE(("evaltree(%p: %d) called\n", (void *)n, n->type));
  		switch (n->type) {
  		case NSEMI:
  			evaltree(n->nbinary.ch1, flags & ~EV_EXIT);
  			if (evalskip)
  				goto out;
  			next = n->nbinary.ch2;
  			break;
  		case NAND:
  			evaltree(n->nbinary.ch1, EV_TESTED);
  			if (evalskip || exitstatus != 0) {
  				goto out;
  			}
  			next = n->nbinary.ch2;
  			break;
  		case NOR:
  			evaltree(n->nbinary.ch1, EV_TESTED);
  			if (evalskip || exitstatus == 0)
  				goto out;
  			next = n->nbinary.ch2;
  			break;
  		case NREDIR:
  			evalredir(n, flags);
  			break;
  		case NSUBSHELL:
  			evalsubshell(n, flags);
  			do_etest = !(flags & EV_TESTED);
  			break;
  		case NBACKGND:
  			evalsubshell(n, flags);
  			break;
  		case NIF: {
  			evaltree(n->nif.test, EV_TESTED);
  			if (evalskip)
  				goto out;
  			if (exitstatus == 0)
  				next = n->nif.ifpart;
  			else if (n->nif.elsepart)
  				next = n->nif.elsepart;
  			else
  				exitstatus = 0;
  			break;
  		}
  		case NWHILE:
  		case NUNTIL:
  			evalloop(n, flags & ~EV_EXIT);
  			break;
  		case NFOR:
  			evalfor(n, flags & ~EV_EXIT);
  			break;
  		case NCASE:
  			next = evalcase(n);
  			break;
  		case NCLIST:
  			next = n->nclist.body;
  			break;
  		case NCLISTFALLTHRU:
  			if (n->nclist.body) {
  				evaltree(n->nclist.body, flags & ~EV_EXIT);
  				if (evalskip)
  					goto out;
  			}
  			next = n->nclist.next;
  			break;
  		case NDEFUN:
  			defun(n->narg.text, n->narg.next);
  			exitstatus = 0;
  			break;
  		case NNOT:
  			evaltree(n->nnot.com, EV_TESTED);
  			if (evalskip)
  				goto out;
  			exitstatus = !exitstatus;
  			break;
  
  		case NPIPE:
  			evalpipe(n);
  			do_etest = !(flags & EV_TESTED);
  			break;
  		case NCMD:
  			evalcommand(n, flags, (struct backcmd *)NULL);
  			do_etest = !(flags & EV_TESTED);
  			break;
  		default:
  			out1fmt("Node type = %d\n", n->type);
  			flushout(&output);
  			break;
  		}
  		n = next;
  		popstackmark(&smark);
  		setstackmark(&smark);
  	} while (n != NULL);
  out:
  	popstackmark(&smark);
  	if (pendingsig)
  		dotrap();
  	if (eflag && exitstatus != 0 && do_etest)
  		exitshell(exitstatus);
  	if (flags & EV_EXIT)
  		exraise(EXEXIT);
  }
  
  
  static void
  evalloop(union node *n, int flags)
  {
  	int status;
  
  	loopnest++;
  	status = 0;
  	for (;;) {
  		if (!evalskip)
  			evaltree(n->nbinary.ch1, EV_TESTED);
  		if (evalskip) {
  			if (evalskip == SKIPCONT && --skipcount <= 0) {
  				evalskip = 0;
  				continue;
  			}
  			if (evalskip == SKIPBREAK && --skipcount <= 0)
  				evalskip = 0;
  			if (evalskip == SKIPRETURN)
  				status = exitstatus;
  			break;
  		}
  		if (n->type == NWHILE) {
  			if (exitstatus != 0)
  				break;
  		} else {
  			if (exitstatus == 0)
  				break;
  		}
  		evaltree(n->nbinary.ch2, flags);
  		status = exitstatus;
  	}
  	loopnest--;
  	exitstatus = status;
  }
  
  
  
  static void
  evalfor(union node *n, int flags)
  {
  	struct arglist arglist;
  	union node *argp;
  	int i;
  	int status;
  
  	emptyarglist(&arglist);
  	for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
  		oexitstatus = exitstatus;
  		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
  	}
  
  	loopnest++;
  	status = 0;
  	for (i = 0; i < arglist.count; i++) {
  		setvar(n->nfor.var, arglist.args[i], 0);
  		evaltree(n->nfor.body, flags);
  		status = exitstatus;
  		if (evalskip) {
  			if (evalskip == SKIPCONT && --skipcount <= 0) {
  				evalskip = 0;
  				continue;
  			}
  			if (evalskip == SKIPBREAK && --skipcount <= 0)
  				evalskip = 0;
  			break;
  		}
  	}
  	loopnest--;
  	exitstatus = status;
  }
  
  
  /*
   * Evaluate a case statement, returning the selected tree.
   *
   * The exit status needs care to get right.
   */
  
  static union node *
  evalcase(union node *n)
  {
  	union node *cp;
  	union node *patp;
  	struct arglist arglist;
  
  	emptyarglist(&arglist);
  	oexitstatus = exitstatus;
  	expandarg(n->ncase.expr, &arglist, EXP_TILDE);
  	for (cp = n->ncase.cases ; cp ; cp = cp->nclist.next) {
  		for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
  			if (casematch(patp, arglist.args[0])) {
  				while (cp->nclist.next &&
  				    cp->type == NCLISTFALLTHRU &&
  				    cp->nclist.body == NULL)
  					cp = cp->nclist.next;
  				if (cp->nclist.next &&
  				    cp->type == NCLISTFALLTHRU)
  					return (cp);
  				if (cp->nclist.body == NULL)
  					exitstatus = 0;
  				return (cp->nclist.body);
  			}
  		}
  	}
  	exitstatus = 0;
  	return (NULL);
  }
  
  
  
  /*
   * Kick off a subshell to evaluate a tree.
   */
  
  static void
  evalsubshell(union node *n, int flags)
  {
  	struct job *jp;
  	int backgnd = (n->type == NBACKGND);
  
  	oexitstatus = exitstatus;
  	expredir(n->nredir.redirect);
  	if ((!backgnd && flags & EV_EXIT && !have_traps()) ||
  			forkshell(jp = makejob(n, 1), n, backgnd) == 0) {
  		if (backgnd)
  			flags &=~ EV_TESTED;
  		redirect(n->nredir.redirect, 0);
  		evaltree(n->nredir.n, flags | EV_EXIT);	/* never returns */
  	} else if (! backgnd) {
  		INTOFF;
  		exitstatus = waitforjob(jp, (int *)NULL);
  		INTON;
  	} else
  		exitstatus = 0;
  }
  
  
  /*
   * Evaluate a redirected compound command.
   */
  
  static void
  evalredir(union node *n, int flags)
  {
  	struct jmploc jmploc;
  	struct jmploc *savehandler;
  	volatile int in_redirect = 1;
  
  	oexitstatus = exitstatus;
  	expredir(n->nredir.redirect);
  	savehandler = handler;
  	if (setjmp(jmploc.loc)) {
  		int e;
  
  		handler = savehandler;
  		e = exception;
  		popredir();
  		if (e == EXERROR || e == EXEXEC) {
  			if (in_redirect) {
  				exitstatus = 2;
  				return;
  			}
  		}
  		longjmp(handler->loc, 1);
  	} else {
  		INTOFF;
  		handler = &jmploc;
  		redirect(n->nredir.redirect, REDIR_PUSH);
  		in_redirect = 0;
  		INTON;
  		evaltree(n->nredir.n, flags);
  	}
  	INTOFF;
  	handler = savehandler;
  	popredir();
  	INTON;
  }
  
  
  static void
  exphere(union node *redir, struct arglist *fn)
  {
  	struct jmploc jmploc;
  	struct jmploc *savehandler;
  	struct localvar *savelocalvars;
  	int need_longjmp = 0;
  	unsigned char saveoptreset;
  
  	redir->nhere.expdoc = "";
  	savelocalvars = localvars;
  	localvars = NULL;
  	saveoptreset = shellparam.reset;
  	forcelocal++;
  	savehandler = handler;
  	if (setjmp(jmploc.loc))
  		need_longjmp = exception != EXERROR && exception != EXEXEC;
  	else {
  		handler = &jmploc;
  		expandarg(redir->nhere.doc, fn, 0);
  		redir->nhere.expdoc = fn->args[0];
  		INTOFF;
  	}
  	handler = savehandler;
  	forcelocal--;
  	poplocalvars();
  	localvars = savelocalvars;
  	shellparam.reset = saveoptreset;
  	if (need_longjmp)
  		longjmp(handler->loc, 1);
  	INTON;
  }
  
  
  /*
   * Compute the names of the files in a redirection list.
   */
  
  static void
  expredir(union node *n)
  {
  	union node *redir;
  
  	for (redir = n ; redir ; redir = redir->nfile.next) {
  		struct arglist fn;
  		emptyarglist(&fn);
  		switch (redir->type) {
  		case NFROM:
  		case NTO:
  		case NFROMTO:
  		case NAPPEND:
  		case NCLOBBER:
  			expandarg(redir->nfile.fname, &fn, EXP_TILDE);
  			redir->nfile.expfname = fn.args[0];
  			break;
  		case NFROMFD:
  		case NTOFD:
  			if (redir->ndup.vname) {
  				expandarg(redir->ndup.vname, &fn, EXP_TILDE);
  				fixredir(redir, fn.args[0], 1);
  			}
  			break;
  		case NXHERE:
  			exphere(redir, &fn);
  			break;
  		}
  	}
  }
  
  
  
  /*
   * Evaluate a pipeline.  All the processes in the pipeline are children
   * of the process creating the pipeline.  (This differs from some versions
   * of the shell, which make the last process in a pipeline the parent
   * of all the rest.)
   */
  
  static void
  evalpipe(union node *n)
  {
  	struct job *jp;
  	struct nodelist *lp;
  	int pipelen;
  	int prevfd;
  	int pip[2];
  
  	TRACE(("evalpipe(%p) called\n", (void *)n));
  	pipelen = 0;
  	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
  		pipelen++;
  	INTOFF;
  	jp = makejob(n, pipelen);
  	prevfd = -1;
  	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
  		prehash(lp->n);
  		pip[1] = -1;
  		if (lp->next) {
  			if (pipe(pip) < 0) {
  				if (prevfd >= 0)
  					close(prevfd);
  				error("Pipe call failed: %s", strerror(errno));
  			}
  		}
  		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
  			INTON;
  			if (prevfd > 0) {
  				dup2(prevfd, 0);
  				close(prevfd);
  			}
  			if (pip[1] >= 0) {
  				if (!(prevfd >= 0 && pip[0] == 0))
  					close(pip[0]);
  				if (pip[1] != 1) {
  					dup2(pip[1], 1);
  					close(pip[1]);
  				}
  			}
  			evaltree(lp->n, EV_EXIT);
  		}
  		if (prevfd >= 0)
  			close(prevfd);
  		prevfd = pip[0];
  		if (pip[1] != -1)
  			close(pip[1]);
  	}
  	INTON;
  	if (n->npipe.backgnd == 0) {
  		INTOFF;
  		exitstatus = waitforjob(jp, (int *)NULL);
  		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
  		INTON;
  	} else
  		exitstatus = 0;
  }
  
  
  
  static int
  is_valid_fast_cmdsubst(union node *n)
  {
  
  	return (n->type == NCMD);
  }
  
  /*
   * Execute a command inside back quotes.  If it's a builtin command, we
   * want to save its output in a block obtained from malloc.  Otherwise
   * we fork off a subprocess and get the output of the command via a pipe.
   * Should be called with interrupts off.
   */
  
  void
  evalbackcmd(union node *n, struct backcmd *result)
  {
  	int pip[2];
  	struct job *jp;
  	struct stackmark smark;
  	struct jmploc jmploc;
  	struct jmploc *savehandler;
  	struct localvar *savelocalvars;
  	unsigned char saveoptreset;
  
  	result->fd = -1;
  	result->buf = NULL;
  	result->nleft = 0;
  	result->jp = NULL;
  	if (n == NULL) {
  		exitstatus = 0;
  		return;
  	}
  	setstackmark(&smark);
  	exitstatus = oexitstatus;
  	if (is_valid_fast_cmdsubst(n)) {
  		savelocalvars = localvars;
  		localvars = NULL;
  		saveoptreset = shellparam.reset;
  		forcelocal++;
  		savehandler = handler;
  		if (setjmp(jmploc.loc)) {
  			if (exception == EXERROR || exception == EXEXEC)
  				exitstatus = 2;
  			else if (exception != 0) {
  				handler = savehandler;
  				forcelocal--;
  				poplocalvars();
  				localvars = savelocalvars;
  				shellparam.reset = saveoptreset;
  				longjmp(handler->loc, 1);
  			}
  		} else {
  			handler = &jmploc;
  			evalcommand(n, EV_BACKCMD, result);
  		}
  		handler = savehandler;
  		forcelocal--;
  		poplocalvars();
  		localvars = savelocalvars;
  		shellparam.reset = saveoptreset;
  	} else {
  		if (pipe(pip) < 0)
  			error("Pipe call failed: %s", strerror(errno));
  		jp = makejob(n, 1);
  		if (forkshell(jp, n, FORK_NOJOB) == 0) {
  			FORCEINTON;
  			close(pip[0]);
  			if (pip[1] != 1) {
  				dup2(pip[1], 1);
  				close(pip[1]);
  			}
  			evaltree(n, EV_EXIT);
  		}
  		close(pip[1]);
  		result->fd = pip[0];
  		result->jp = jp;
  	}
  	popstackmark(&smark);
  	TRACE(("evalbackcmd done: fd=%d buf=%p nleft=%d jp=%p\n",
  		result->fd, result->buf, result->nleft, result->jp));
  }
  
  static int
  mustexpandto(const char *argtext, const char *mask)
  {
  	for (;;) {
  		if (*argtext == CTLQUOTEMARK || *argtext == CTLQUOTEEND) {
  			argtext++;
  			continue;
  		}
  		if (*argtext == CTLESC)
  			argtext++;
  		else if (BASESYNTAX[(int)*argtext] == CCTL)
  			return (0);
  		if (*argtext != *mask)
  			return (0);
  		if (*argtext == '\0')
  			return (1);
  		argtext++;
  		mask++;
  	}
  }
  
  static int
  isdeclarationcmd(struct narg *arg)
  {
  	int have_command = 0;
  
  	if (arg == NULL)
  		return (0);
  	while (mustexpandto(arg->text, "command")) {
  		have_command = 1;
  		arg = &arg->next->narg;
  		if (arg == NULL)
  			return (0);
  		/*
  		 * To also allow "command -p" and "command --" as part of
  		 * a declaration command, add code here.
  		 * We do not do this, as ksh does not do it either and it
  		 * is not required by POSIX.
  		 */
  	}
  	return (mustexpandto(arg->text, "export") ||
  	    mustexpandto(arg->text, "readonly") ||
  	    (mustexpandto(arg->text, "local") &&
  		(have_command || !isfunc("local"))));
  }
  
  static void
  xtracecommand(struct arglist *varlist, int argc, char **argv)
  {
  	char sep = 0;
  	const char *text, *p, *ps4;
  	int i;
  
  	ps4 = expandstr(ps4val());
  	out2str(ps4 != NULL ? ps4 : ps4val());
  	for (i = 0; i < varlist->count; i++) {
  		text = varlist->args[i];
  		if (sep != 0)
  			out2c(' ');
  		p = strchr(text, '=');
  		if (p != NULL) {
  			p++;
  			outbin(text, p - text, out2);
  			out2qstr(p);
  		} else
  			out2qstr(text);
  		sep = ' ';
  	}
  	for (i = 0; i < argc; i++) {
  		text = argv[i];
  		if (sep != 0)
  			out2c(' ');
  		out2qstr(text);
  		sep = ' ';
  	}
  	out2c('\n');
  	flushout(&errout);
  }
  
  /*
   * Check if a builtin can safely be executed in the same process,
   * even though it should be in a subshell (command substitution).
   * Note that jobid, jobs, times and trap can show information not
   * available in a child process; this is deliberate.
   * The arguments should already have been expanded.
   */
  static int
  safe_builtin(int idx, int argc, char **argv)
  {
  	if (idx == BLTINCMD || idx == COMMANDCMD || idx == ECHOCMD ||
  	    idx == FALSECMD || idx == JOBIDCMD || idx == JOBSCMD ||
  	    idx == KILLCMD || idx == PRINTFCMD || idx == PWDCMD ||
  	    idx == TESTCMD || idx == TIMESCMD || idx == TRUECMD ||
  	    idx == TYPECMD)
  		return (1);
  	if (idx == EXPORTCMD || idx == TRAPCMD || idx == ULIMITCMD ||
  	    idx == UMASKCMD)
  		return (argc <= 1 || (argc == 2 && argv[1][0] == '-'));
  	if (idx == SETCMD)
  		return (argc <= 1 || (argc == 2 && (argv[1][0] == '-' ||
  		    argv[1][0] == '+') && argv[1][1] == 'o' &&
  		    argv[1][2] == '\0'));
  	return (0);
  }
  
  /*
   * Execute a simple command.
   * Note: This may or may not return if (flags & EV_EXIT).
   */
  
  static void
  evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
  {
  	union node *argp;
  	struct arglist arglist;
  	struct arglist varlist;
  	char **argv;
  	int argc;
  	char **envp;
  	int varflag;
  	int mode;
  	int pip[2];
  	struct cmdentry cmdentry;
  	struct job *jp;
  	struct jmploc jmploc;
  	struct jmploc *savehandler;
  	char *savecmdname;
  	struct shparam saveparam;
  	struct localvar *savelocalvars;
  	struct parsefile *savetopfile;
  	volatile int e;
  	char *lastarg;
  	int realstatus;
  	int do_clearcmdentry;
  	const char *path = pathval();
  	int i;
  
  	/* First expand the arguments. */
  	TRACE(("evalcommand(%p, %d) called\n", (void *)cmd, flags));
  	emptyarglist(&arglist);
  	emptyarglist(&varlist);
  	varflag = 1;
  	jp = NULL;
  	do_clearcmdentry = 0;
  	oexitstatus = exitstatus;
  	exitstatus = 0;
  	/* Add one slot at the beginning for tryexec(). */
  	appendarglist(&arglist, nullstr);
  	for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
  		if (varflag && isassignment(argp->narg.text)) {
  			expandarg(argp, varflag == 1 ? &varlist : &arglist,
  			    EXP_VARTILDE);
  			continue;
  		} else if (varflag == 1)
  			varflag = isdeclarationcmd(&argp->narg) ? 2 : 0;
  		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
  	}
  	appendarglist(&arglist, nullstr);
  	expredir(cmd->ncmd.redirect);
  	argc = arglist.count - 2;
  	argv = &arglist.args[1];
  
  	argv[argc] = NULL;
  	lastarg = NULL;
  	if (iflag && funcnest == 0 && argc > 0)
  		lastarg = argv[argc - 1];
  
  	/* Print the command if xflag is set. */
  	if (xflag)
  		xtracecommand(&varlist, argc, argv);
  
  	/* Now locate the command. */
  	if (argc == 0) {
  		/* Variable assignment(s) without command */
  		cmdentry.cmdtype = CMDBUILTIN;
  		cmdentry.u.index = BLTINCMD;
  		cmdentry.special = 0;
  	} else {
  		static const char PATH[] = "PATH=";
  		int cmd_flags = 0, bltinonly = 0;
  
  		/*
  		 * Modify the command lookup path, if a PATH= assignment
  		 * is present
  		 */
  		for (i = 0; i < varlist.count; i++)
  			if (strncmp(varlist.args[i], PATH, sizeof(PATH) - 1) == 0) {
  				path = varlist.args[i] + sizeof(PATH) - 1;
  				/*
  				 * On `PATH=... command`, we need to make
  				 * sure that the command isn't using the
  				 * non-updated hash table of the outer PATH
  				 * setting and we need to make sure that
  				 * the hash table isn't filled with items
  				 * from the temporary setting.
  				 *
  				 * It would be better to forbit using and
  				 * updating the table while this command
  				 * runs, by the command finding mechanism
  				 * is heavily integrated with hash handling,
  				 * so we just delete the hash before and after
  				 * the command runs. Partly deleting like
  				 * changepatch() does doesn't seem worth the
  				 * bookinging effort, since most such runs add
  				 * directories in front of the new PATH.
  				 */
  				clearcmdentry();
  				do_clearcmdentry = 1;
  			}
  
  		for (;;) {
  			if (bltinonly) {
  				cmdentry.u.index = find_builtin(*argv, &cmdentry.special);
  				if (cmdentry.u.index < 0) {
  					cmdentry.u.index = BLTINCMD;
  					argv--;
  					argc++;
  					break;
  				}
  			} else
  				find_command(argv[0], &cmdentry, cmd_flags, path);
  			/* implement the bltin and command builtins here */
  			if (cmdentry.cmdtype != CMDBUILTIN)
  				break;
  			if (cmdentry.u.index == BLTINCMD) {
  				if (argc == 1)
  					break;
  				argv++;
  				argc--;
  				bltinonly = 1;
  			} else if (cmdentry.u.index == COMMANDCMD) {
  				if (argc == 1)
  					break;
  				if (!strcmp(argv[1], "-p")) {
  					if (argc == 2)
  						break;
  					if (argv[2][0] == '-') {
  						if (strcmp(argv[2], "--"))
  							break;
  						if (argc == 3)
  							break;
  						argv += 3;
  						argc -= 3;
  					} else {
  						argv += 2;
  						argc -= 2;
  					}
  					path = _PATH_STDPATH;
  					clearcmdentry();
  					do_clearcmdentry = 1;
  				} else if (!strcmp(argv[1], "--")) {
  					if (argc == 2)
  						break;
  					argv += 2;
  					argc -= 2;
  				} else if (argv[1][0] == '-')
  					break;
  				else {
  					argv++;
  					argc--;
  				}
  				cmd_flags |= DO_NOFUNC;
  				bltinonly = 0;
  			} else
  				break;
  		}
  		/*
  		 * Special builtins lose their special properties when
  		 * called via 'command'.
  		 */
  		if (cmd_flags & DO_NOFUNC)
  			cmdentry.special = 0;
  	}
  
  	/* Fork off a child process if necessary. */
  	if (((cmdentry.cmdtype == CMDNORMAL || cmdentry.cmdtype == CMDUNKNOWN)
  	    && ((flags & EV_EXIT) == 0 || have_traps()))
  	 || ((flags & EV_BACKCMD) != 0
  	    && (cmdentry.cmdtype != CMDBUILTIN ||
  		 !safe_builtin(cmdentry.u.index, argc, argv)))) {
  		jp = makejob(cmd, 1);
  		mode = FORK_FG;
  		if (flags & EV_BACKCMD) {
  			mode = FORK_NOJOB;
  			if (pipe(pip) < 0)
  				error("Pipe call failed: %s", strerror(errno));
  		}
  		if (cmdentry.cmdtype == CMDNORMAL &&
  		    cmd->ncmd.redirect == NULL &&
  		    varlist.count == 0 &&
  		    (mode == FORK_FG || mode == FORK_NOJOB) &&
  		    !disvforkset() && !iflag && !mflag) {
  			vforkexecshell(jp, argv, environment(), path,
  			    cmdentry.u.index, flags & EV_BACKCMD ? pip : NULL);
  			goto parent;
  		}
  		if (forkshell(jp, cmd, mode) != 0)
  			goto parent;	/* at end of routine */
  		if (flags & EV_BACKCMD) {
  			FORCEINTON;
  			close(pip[0]);
  			if (pip[1] != 1) {
  				dup2(pip[1], 1);
  				close(pip[1]);
  			}
  			flags &= ~EV_BACKCMD;
  		}
  		flags |= EV_EXIT;
  	}
  
  	/* This is the child process if a fork occurred. */
  	/* Execute the command. */
  	if (cmdentry.cmdtype == CMDFUNCTION) {
  #ifdef DEBUG
  		trputs("Shell function:  ");  trargs(argv);
  #endif
  		saveparam = shellparam;
  		shellparam.malloc = 0;
  		shellparam.reset = 1;
  		shellparam.nparam = argc - 1;
  		shellparam.p = argv + 1;
  		shellparam.optp = NULL;
  		shellparam.optnext = NULL;
  		INTOFF;
  		savelocalvars = localvars;
  		localvars = NULL;
  		reffunc(cmdentry.u.func);
  		savehandler = handler;
  		if (setjmp(jmploc.loc)) {
  			popredir();
  			unreffunc(cmdentry.u.func);
  			poplocalvars();
  			localvars = savelocalvars;
  			freeparam(&shellparam);
  			shellparam = saveparam;
  			funcnest--;
  			handler = savehandler;
  			longjmp(handler->loc, 1);
  		}
  		handler = &jmploc;
  		funcnest++;
  		redirect(cmd->ncmd.redirect, REDIR_PUSH);
  		INTON;
  		for (i = 0; i < varlist.count; i++)
  			mklocal(varlist.args[i]);
  		exitstatus = oexitstatus;
  		evaltree(getfuncnode(cmdentry.u.func),
  		    flags & (EV_TESTED | EV_EXIT));
  		INTOFF;
  		unreffunc(cmdentry.u.func);
  		poplocalvars();
  		localvars = savelocalvars;
  		freeparam(&shellparam);
  		shellparam = saveparam;
  		handler = savehandler;
  		funcnest--;
  		popredir();
  		INTON;
  		if (evalskip == SKIPRETURN) {
  			evalskip = 0;
  			skipcount = 0;
  		}
  		if (jp)
  			exitshell(exitstatus);
  	} else if (cmdentry.cmdtype == CMDBUILTIN) {
  #ifdef DEBUG
  		trputs("builtin command:  ");  trargs(argv);
  #endif
  		mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
  		if (flags == EV_BACKCMD) {
  			memout.nleft = 0;
  			memout.nextc = memout.buf;
  			memout.bufsize = 64;
  			mode |= REDIR_BACKQ;
  		}
  		savecmdname = commandname;
  		savetopfile = getcurrentfile();
  		cmdenviron = &varlist;
  		e = -1;
  		savehandler = handler;
  		if (setjmp(jmploc.loc)) {
  			e = exception;
  			if (e == EXINT)
  				exitstatus = SIGINT+128;
  			else if (e != EXEXIT)
  				exitstatus = 2;
  			goto cmddone;
  		}
  		handler = &jmploc;
  		redirect(cmd->ncmd.redirect, mode);
  		outclearerror(out1);
  		/*
  		 * If there is no command word, redirection errors should
  		 * not be fatal but assignment errors should.
  		 */
  		if (argc == 0)
  			cmdentry.special = 1;
  		listsetvar(cmdenviron, cmdentry.special ? 0 : VNOSET);
  		if (argc > 0)
  			bltinsetlocale();
  		commandname = argv[0];
  		argptr = argv + 1;
  		nextopt_optptr = NULL;		/* initialize nextopt */
  		builtin_flags = flags;
  		exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
  		flushall();
  		if (outiserror(out1)) {
  			warning("write error on stdout");
  			if (exitstatus == 0 || exitstatus == 1)
  				exitstatus = 2;
  		}
  cmddone:
  		if (argc > 0)
  			bltinunsetlocale();
  		cmdenviron = NULL;
  		out1 = &output;
  		out2 = &errout;
  		freestdout();
  		handler = savehandler;
  		commandname = savecmdname;
  		if (jp)
  			exitshell(exitstatus);
  		if (flags == EV_BACKCMD) {
  			backcmd->buf = memout.buf;
  			backcmd->nleft = memout.nextc - memout.buf;
  			memout.buf = NULL;
  		}
  		if (cmdentry.u.index != EXECCMD)
  			popredir();
  		if (e != -1) {
  			if ((e != EXERROR && e != EXEXEC)
  			    || cmdentry.special)
  				exraise(e);
  			popfilesupto(savetopfile);
  			if (flags != EV_BACKCMD)
  				FORCEINTON;
  		}
  	} else {
  #ifdef DEBUG
  		trputs("normal command:  ");  trargs(argv);
  #endif
  		redirect(cmd->ncmd.redirect, 0);
  		for (i = 0; i < varlist.count; i++)
  			setvareq(varlist.args[i], VEXPORT|VSTACK);
  		envp = environment();
  		shellexec(argv, envp, path, cmdentry.u.index);
  		/*NOTREACHED*/
  	}
  	goto out;
  
  parent:	/* parent process gets here (if we forked) */
  	if (mode == FORK_FG) {	/* argument to fork */
  		INTOFF;
  		exitstatus = waitforjob(jp, &realstatus);
  		INTON;
  		if (iflag && loopnest > 0 && WIFSIGNALED(realstatus)) {
  			evalskip = SKIPBREAK;
  			skipcount = loopnest;
  		}
  	} else if (mode == FORK_NOJOB) {
  		backcmd->fd = pip[0];
  		close(pip[1]);
  		backcmd->jp = jp;
  	}
  
  out:
  	if (lastarg)
  		setvar("_", lastarg, 0);
  	if (do_clearcmdentry)
  		clearcmdentry();
  }
  
  
  
  /*
   * Search for a command.  This is called before we fork so that the
   * location of the command will be available in the parent as well as
   * the child.  The check for "goodname" is an overly conservative
   * check that the name will not be subject to expansion.
   */
  
  static void
  prehash(union node *n)
  {
  	struct cmdentry entry;
  
  	if (n && n->type == NCMD && n->ncmd.args)
  		if (goodname(n->ncmd.args->narg.text))
  			find_command(n->ncmd.args->narg.text, &entry, 0,
  				     pathval());
  }
  
  
  
  /*
   * Builtin commands.  Builtin commands whose functions are closely
   * tied to evaluation are implemented here.
   */
  
  /*
   * No command given, a bltin command with no arguments, or a bltin command
   * with an invalid name.
   */
  
  int
  bltincmd(int argc, char **argv)
  {
  	if (argc > 1) {
  		out2fmt_flush("%s: not found\n", argv[1]);
  		return 127;
  	}
  	/*
  	 * Preserve exitstatus of a previous possible redirection
  	 * as POSIX mandates
  	 */
  	return exitstatus;
  }
  
  
  /*
   * Handle break and continue commands.  Break, continue, and return are
   * all handled by setting the evalskip flag.  The evaluation routines
   * above all check this flag, and if it is set they start skipping
   * commands rather than executing them.  The variable skipcount is
   * the number of loops to break/continue, or the number of function
   * levels to return.  (The latter is always 1.)  It should probably
   * be an error to break out of more loops than exist, but it isn't
   * in the standard shell so we don't make it one here.
   */
  
  int
  breakcmd(int argc, char **argv)
  {
  	long n;
  	char *end;
  
  	if (argc > 1) {
  		/* Allow arbitrarily large numbers. */
  		n = strtol(argv[1], &end, 10);
  		if (!is_digit(argv[1][0]) || *end != '\0')
  			error("Illegal number: %s", argv[1]);
  	} else
  		n = 1;
  	if (n > loopnest)
  		n = loopnest;
  	if (n > 0) {
  		evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
  		skipcount = n;
  	}
  	return 0;
  }
  
  /*
   * The `command' command.
   */
  int
  commandcmd(int argc __unused, char **argv __unused)
  {
  	const char *path;
  	int ch;
  	int cmd = -1;
  
  	path = bltinlookup("PATH", 1);
  
  	while ((ch = nextopt("pvV")) != '\0') {
  		switch (ch) {
  		case 'p':
  			path = _PATH_STDPATH;
  			break;
  		case 'v':
  			cmd = TYPECMD_SMALLV;
  			break;
  		case 'V':
  			cmd = TYPECMD_BIGV;
  			break;
  		}
  	}
  
  	if (cmd != -1) {
  		if (*argptr == NULL || argptr[1] != NULL)
  			error("wrong number of arguments");
  		return typecmd_impl(2, argptr - 1, cmd, path);
  	}
  	if (*argptr != NULL)
  		error("commandcmd bad call");
  
  	/*
  	 * Do nothing successfully if no command was specified;
  	 * ksh also does this.
  	 */
  	return 0;
  }
  
  
  /*
   * The return command.
   */
  
  int
  returncmd(int argc, char **argv)
  {
  	int ret = argc > 1 ? number(argv[1]) : oexitstatus;
  
  	evalskip = SKIPRETURN;
  	skipcount = 1;
  	return ret;
  }
  
  
  int
  falsecmd(int argc __unused, char **argv __unused)
  {
  	return 1;
  }
  
  
  int
  truecmd(int argc __unused, char **argv __unused)
  {
  	return 0;
  }
  
  
  int
  execcmd(int argc, char **argv)
  {
  	int i;
  
  	/*
  	 * Because we have historically not supported any options,
  	 * only treat "--" specially.
  	 */
  	if (argc > 1 && strcmp(argv[1], "--") == 0)
  		argc--, argv++;
  	if (argc > 1) {
  		iflag = 0;		/* exit on error */
  		mflag = 0;
  		optschanged();
  		for (i = 0; i < cmdenviron->count; i++)
  			setvareq(cmdenviron->args[i], VEXPORT|VSTACK);
  		shellexec(argv + 1, environment(), pathval(), 0);
  
  	}
  	return 0;
  }
  
  
  int
  timescmd(int argc __unused, char **argv __unused)
  {
  	struct rusage ru;
  	long shumins, shsmins, chumins, chsmins;
  	double shusecs, shssecs, chusecs, chssecs;
  
  	if (getrusage(RUSAGE_SELF, &ru) < 0)
  		return 1;
  	shumins = ru.ru_utime.tv_sec / 60;
  	shusecs = ru.ru_utime.tv_sec % 60 + ru.ru_utime.tv_usec / 1000000.;
  	shsmins = ru.ru_stime.tv_sec / 60;
  	shssecs = ru.ru_stime.tv_sec % 60 + ru.ru_stime.tv_usec / 1000000.;
  	if (getrusage(RUSAGE_CHILDREN, &ru) < 0)
  		return 1;
  	chumins = ru.ru_utime.tv_sec / 60;
  	chusecs = ru.ru_utime.tv_sec % 60 + ru.ru_utime.tv_usec / 1000000.;
  	chsmins = ru.ru_stime.tv_sec / 60;
  	chssecs = ru.ru_stime.tv_sec % 60 + ru.ru_stime.tv_usec / 1000000.;
  	out1fmt("%ldm%.3fs %ldm%.3fs\n%ldm%.3fs %ldm%.3fs\n", shumins,
  	    shusecs, shsmins, shssecs, chumins, chusecs, chsmins, chssecs);
  	return 0;
  }
  