eval.c revision 127958 
1/*-
2 * Copyright (c) 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Kenneth Almquist.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#ifndef lint
34#if 0
35static char sccsid[] = "@(#)eval.c	8.9 (Berkeley) 6/8/95";
36#endif
37#endif /* not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: head/bin/sh/eval.c 127958 2004-04-06 20:06:54Z markm $");
40
41#include <paths.h>
42#include <signal.h>
43#include <stdlib.h>
44#include <unistd.h>
45#include <sys/wait.h> /* For WIFSIGNALED(status) */
46#include <errno.h>
47
48/*
49 * Evaluate a command.
50 */
51
52#include "shell.h"
53#include "nodes.h"
54#include "syntax.h"
55#include "expand.h"
56#include "parser.h"
57#include "jobs.h"
58#include "eval.h"
59#include "builtins.h"
60#include "options.h"
61#include "exec.h"
62#include "redir.h"
63#include "input.h"
64#include "output.h"
65#include "trap.h"
66#include "var.h"
67#include "memalloc.h"
68#include "error.h"
69#include "show.h"
70#include "mystring.h"
71#ifndef NO_HISTORY
72#include "myhistedit.h"
73#endif
74
75
76/* flags in argument to evaltree */
77#define EV_EXIT 01		/* exit after evaluating tree */
78#define EV_TESTED 02		/* exit status is checked; ignore -e flag */
79#define EV_BACKCMD 04		/* command executing within back quotes */
80
81MKINIT int evalskip;		/* set if we are skipping commands */
82STATIC int skipcount;		/* number of levels to skip */
83MKINIT int loopnest;		/* current loop nesting level */
84int funcnest;			/* depth of function calls */
85
86
87char *commandname;
88struct strlist *cmdenviron;
89int exitstatus;			/* exit status of last command */
90int oexitstatus;		/* saved exit status */
91
92
93STATIC void evalloop(union node *);
94STATIC void evalfor(union node *);
95STATIC void evalcase(union node *, int);
96STATIC void evalsubshell(union node *, int);
97STATIC void expredir(union node *);
98STATIC void evalpipe(union node *);
99STATIC void evalcommand(union node *, int, struct backcmd *);
100STATIC void prehash(union node *);
101
102
103/*
104 * Called to reset things after an exception.
105 */
106
107#ifdef mkinit
108INCLUDE "eval.h"
109
110RESET {
111	evalskip = 0;
112	loopnest = 0;
113	funcnest = 0;
114}
115
116SHELLPROC {
117	exitstatus = 0;
118}
119#endif
120
121
122
123/*
124 * The eval command.
125 */
126
127int
128evalcmd(int argc, char **argv)
129{
130        char *p;
131        char *concat;
132        char **ap;
133
134        if (argc > 1) {
135                p = argv[1];
136                if (argc > 2) {
137                        STARTSTACKSTR(concat);
138                        ap = argv + 2;
139                        for (;;) {
140                                while (*p)
141                                        STPUTC(*p++, concat);
142                                if ((p = *ap++) == NULL)
143                                        break;
144                                STPUTC(' ', concat);
145                        }
146                        STPUTC('\0', concat);
147                        p = grabstackstr(concat);
148                }
149                evalstring(p);
150        }
151        return exitstatus;
152}
153
154
155/*
156 * Execute a command or commands contained in a string.
157 */
158
159void
160evalstring(char *s)
161{
162	union node *n;
163	struct stackmark smark;
164
165	setstackmark(&smark);
166	setinputstring(s, 1);
167	while ((n = parsecmd(0)) != NEOF) {
168		evaltree(n, 0);
169		popstackmark(&smark);
170	}
171	popfile();
172	popstackmark(&smark);
173}
174
175
176
177/*
178 * Evaluate a parse tree.  The value is left in the global variable
179 * exitstatus.
180 */
181
182void
183evaltree(union node *n, int flags)
184{
185	if (n == NULL) {
186		TRACE(("evaltree(NULL) called\n"));
187		exitstatus = 0;
188		goto out;
189	}
190#ifndef NO_HISTORY
191	displayhist = 1;	/* show history substitutions done with fc */
192#endif
193	TRACE(("evaltree(0x%lx: %d) called\n", (long)n, n->type));
194	switch (n->type) {
195	case NSEMI:
196		evaltree(n->nbinary.ch1, 0);
197		if (evalskip)
198			goto out;
199		evaltree(n->nbinary.ch2, flags);
200		break;
201	case NAND:
202		evaltree(n->nbinary.ch1, EV_TESTED);
203		if (evalskip || exitstatus != 0) {
204			goto out;
205		}
206		evaltree(n->nbinary.ch2, flags);
207		break;
208	case NOR:
209		evaltree(n->nbinary.ch1, EV_TESTED);
210		if (evalskip || exitstatus == 0)
211			goto out;
212		evaltree(n->nbinary.ch2, flags);
213		break;
214	case NREDIR:
215		expredir(n->nredir.redirect);
216		redirect(n->nredir.redirect, REDIR_PUSH);
217		evaltree(n->nredir.n, flags);
218		popredir();
219		break;
220	case NSUBSHELL:
221		evalsubshell(n, flags);
222		break;
223	case NBACKGND:
224		evalsubshell(n, flags);
225		break;
226	case NIF: {
227		evaltree(n->nif.test, EV_TESTED);
228		if (evalskip)
229			goto out;
230		if (exitstatus == 0)
231			evaltree(n->nif.ifpart, flags);
232		else if (n->nif.elsepart)
233			evaltree(n->nif.elsepart, flags);
234		else
235			exitstatus = 0;
236		break;
237	}
238	case NWHILE:
239	case NUNTIL:
240		evalloop(n);
241		break;
242	case NFOR:
243		evalfor(n);
244		break;
245	case NCASE:
246		evalcase(n, flags);
247		break;
248	case NDEFUN:
249		defun(n->narg.text, n->narg.next);
250		exitstatus = 0;
251		break;
252	case NNOT:
253		evaltree(n->nnot.com, EV_TESTED);
254		exitstatus = !exitstatus;
255		break;
256
257	case NPIPE:
258		evalpipe(n);
259		break;
260	case NCMD:
261		evalcommand(n, flags, (struct backcmd *)NULL);
262		break;
263	default:
264		out1fmt("Node type = %d\n", n->type);
265		flushout(&output);
266		break;
267	}
268out:
269	if (pendingsigs)
270		dotrap();
271	if ((flags & EV_EXIT) || (eflag && exitstatus
272	    && !(flags & EV_TESTED) && (n->type == NCMD ||
273	    n->type == NSUBSHELL)))
274		exitshell(exitstatus);
275}
276
277
278STATIC void
279evalloop(union node *n)
280{
281	int status;
282
283	loopnest++;
284	status = 0;
285	for (;;) {
286		evaltree(n->nbinary.ch1, EV_TESTED);
287		if (evalskip) {
288skipping:	  if (evalskip == SKIPCONT && --skipcount <= 0) {
289				evalskip = 0;
290				continue;
291			}
292			if (evalskip == SKIPBREAK && --skipcount <= 0)
293				evalskip = 0;
294			break;
295		}
296		if (n->type == NWHILE) {
297			if (exitstatus != 0)
298				break;
299		} else {
300			if (exitstatus == 0)
301				break;
302		}
303		evaltree(n->nbinary.ch2, 0);
304		status = exitstatus;
305		if (evalskip)
306			goto skipping;
307	}
308	loopnest--;
309	exitstatus = status;
310}
311
312
313
314STATIC void
315evalfor(union node *n)
316{
317	struct arglist arglist;
318	union node *argp;
319	struct strlist *sp;
320	struct stackmark smark;
321
322	setstackmark(&smark);
323	arglist.lastp = &arglist.list;
324	for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
325		oexitstatus = exitstatus;
326		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
327		if (evalskip)
328			goto out;
329	}
330	*arglist.lastp = NULL;
331
332	exitstatus = 0;
333	loopnest++;
334	for (sp = arglist.list ; sp ; sp = sp->next) {
335		setvar(n->nfor.var, sp->text, 0);
336		evaltree(n->nfor.body, 0);
337		if (evalskip) {
338			if (evalskip == SKIPCONT && --skipcount <= 0) {
339				evalskip = 0;
340				continue;
341			}
342			if (evalskip == SKIPBREAK && --skipcount <= 0)
343				evalskip = 0;
344			break;
345		}
346	}
347	loopnest--;
348out:
349	popstackmark(&smark);
350}
351
352
353
354STATIC void
355evalcase(union node *n, int flags)
356{
357	union node *cp;
358	union node *patp;
359	struct arglist arglist;
360	struct stackmark smark;
361
362	setstackmark(&smark);
363	arglist.lastp = &arglist.list;
364	oexitstatus = exitstatus;
365	expandarg(n->ncase.expr, &arglist, EXP_TILDE);
366	for (cp = n->ncase.cases ; cp && evalskip == 0 ; cp = cp->nclist.next) {
367		for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
368			if (casematch(patp, arglist.list->text)) {
369				if (evalskip == 0) {
370					evaltree(cp->nclist.body, flags);
371				}
372				goto out;
373			}
374		}
375	}
376out:
377	popstackmark(&smark);
378}
379
380
381
382/*
383 * Kick off a subshell to evaluate a tree.
384 */
385
386STATIC void
387evalsubshell(union node *n, int flags)
388{
389	struct job *jp;
390	int backgnd = (n->type == NBACKGND);
391
392	expredir(n->nredir.redirect);
393	jp = makejob(n, 1);
394	if (forkshell(jp, n, backgnd) == 0) {
395		if (backgnd)
396			flags &=~ EV_TESTED;
397		redirect(n->nredir.redirect, 0);
398		evaltree(n->nredir.n, flags | EV_EXIT);	/* never returns */
399	}
400	if (! backgnd) {
401		INTOFF;
402		exitstatus = waitforjob(jp, (int *)NULL);
403		INTON;
404	}
405}
406
407
408
409/*
410 * Compute the names of the files in a redirection list.
411 */
412
413STATIC void
414expredir(union node *n)
415{
416	union node *redir;
417
418	for (redir = n ; redir ; redir = redir->nfile.next) {
419		struct arglist fn;
420		fn.lastp = &fn.list;
421		oexitstatus = exitstatus;
422		switch (redir->type) {
423		case NFROM:
424		case NTO:
425		case NFROMTO:
426		case NAPPEND:
427		case NCLOBBER:
428			expandarg(redir->nfile.fname, &fn, EXP_TILDE | EXP_REDIR);
429			redir->nfile.expfname = fn.list->text;
430			break;
431		case NFROMFD:
432		case NTOFD:
433			if (redir->ndup.vname) {
434				expandarg(redir->ndup.vname, &fn, EXP_FULL | EXP_TILDE);
435				fixredir(redir, fn.list->text, 1);
436			}
437			break;
438		}
439	}
440}
441
442
443
444/*
445 * Evaluate a pipeline.  All the processes in the pipeline are children
446 * of the process creating the pipeline.  (This differs from some versions
447 * of the shell, which make the last process in a pipeline the parent
448 * of all the rest.)
449 */
450
451STATIC void
452evalpipe(union node *n)
453{
454	struct job *jp;
455	struct nodelist *lp;
456	int pipelen;
457	int prevfd;
458	int pip[2];
459
460	TRACE(("evalpipe(0x%lx) called\n", (long)n));
461	pipelen = 0;
462	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
463		pipelen++;
464	INTOFF;
465	jp = makejob(n, pipelen);
466	prevfd = -1;
467	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
468		prehash(lp->n);
469		pip[1] = -1;
470		if (lp->next) {
471			if (pipe(pip) < 0) {
472				close(prevfd);
473				error("Pipe call failed: %s", strerror(errno));
474			}
475		}
476		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
477			INTON;
478			if (prevfd > 0) {
479				dup2(prevfd, 0);
480				close(prevfd);
481			}
482			if (pip[1] >= 0) {
483				if (!(prevfd >= 0 && pip[0] == 0))
484					close(pip[0]);
485				if (pip[1] != 1) {
486					dup2(pip[1], 1);
487					close(pip[1]);
488				}
489			}
490			evaltree(lp->n, EV_EXIT);
491		}
492		if (prevfd >= 0)
493			close(prevfd);
494		prevfd = pip[0];
495		close(pip[1]);
496	}
497	INTON;
498	if (n->npipe.backgnd == 0) {
499		INTOFF;
500		exitstatus = waitforjob(jp, (int *)NULL);
501		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
502		INTON;
503	}
504}
505
506
507
508/*
509 * Execute a command inside back quotes.  If it's a builtin command, we
510 * want to save its output in a block obtained from malloc.  Otherwise
511 * we fork off a subprocess and get the output of the command via a pipe.
512 * Should be called with interrupts off.
513 */
514
515void
516evalbackcmd(union node *n, struct backcmd *result)
517{
518	int pip[2];
519	struct job *jp;
520	struct stackmark smark;		/* unnecessary */
521
522	setstackmark(&smark);
523	result->fd = -1;
524	result->buf = NULL;
525	result->nleft = 0;
526	result->jp = NULL;
527	if (n == NULL) {
528		exitstatus = 0;
529		goto out;
530	}
531	if (n->type == NCMD) {
532		exitstatus = oexitstatus;
533		evalcommand(n, EV_BACKCMD, result);
534	} else {
535		exitstatus = 0;
536		if (pipe(pip) < 0)
537			error("Pipe call failed: %s", strerror(errno));
538		jp = makejob(n, 1);
539		if (forkshell(jp, n, FORK_NOJOB) == 0) {
540			FORCEINTON;
541			close(pip[0]);
542			if (pip[1] != 1) {
543				dup2(pip[1], 1);
544				close(pip[1]);
545			}
546			evaltree(n, EV_EXIT);
547		}
548		close(pip[1]);
549		result->fd = pip[0];
550		result->jp = jp;
551	}
552out:
553	popstackmark(&smark);
554	TRACE(("evalbackcmd done: fd=%d buf=%p nleft=%d jp=%p\n",
555		result->fd, result->buf, result->nleft, result->jp));
556}
557
558
559
560/*
561 * Execute a simple command.
562 */
563
564STATIC void
565evalcommand(union node *cmd, int flags, struct backcmd *backcmd)
566{
567	struct stackmark smark;
568	union node *argp;
569	struct arglist arglist;
570	struct arglist varlist;
571	char **argv;
572	int argc;
573	char **envp;
574	int varflag;
575	struct strlist *sp;
576	int mode;
577	int pip[2];
578	struct cmdentry cmdentry;
579	struct job *jp;
580	struct jmploc jmploc;
581	struct jmploc *volatile savehandler;
582	char *volatile savecmdname;
583	volatile struct shparam saveparam;
584	struct localvar *volatile savelocalvars;
585	volatile int e;
586	char *lastarg;
587	int realstatus;
588	int do_clearcmdentry;
589#if __GNUC__
590	/* Avoid longjmp clobbering */
591	(void) &argv;
592	(void) &argc;
593	(void) &lastarg;
594	(void) &flags;
595	(void) &do_clearcmdentry;
596#endif
597
598	/* First expand the arguments. */
599	TRACE(("evalcommand(0x%lx, %d) called\n", (long)cmd, flags));
600	setstackmark(&smark);
601	arglist.lastp = &arglist.list;
602	varlist.lastp = &varlist.list;
603	varflag = 1;
604	do_clearcmdentry = 0;
605	oexitstatus = exitstatus;
606	exitstatus = 0;
607	for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
608		char *p = argp->narg.text;
609		if (varflag && is_name(*p)) {
610			do {
611				p++;
612			} while (is_in_name(*p));
613			if (*p == '=') {
614				expandarg(argp, &varlist, EXP_VARTILDE);
615				continue;
616			}
617		}
618		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
619		varflag = 0;
620	}
621	*arglist.lastp = NULL;
622	*varlist.lastp = NULL;
623	expredir(cmd->ncmd.redirect);
624	argc = 0;
625	for (sp = arglist.list ; sp ; sp = sp->next)
626		argc++;
627	argv = stalloc(sizeof (char *) * (argc + 1));
628
629	for (sp = arglist.list ; sp ; sp = sp->next) {
630		TRACE(("evalcommand arg: %s\n", sp->text));
631		*argv++ = sp->text;
632	}
633	*argv = NULL;
634	lastarg = NULL;
635	if (iflag && funcnest == 0 && argc > 0)
636		lastarg = argv[-1];
637	argv -= argc;
638
639	/* Print the command if xflag is set. */
640	if (xflag) {
641		outc('+', &errout);
642		for (sp = varlist.list ; sp ; sp = sp->next) {
643			outc(' ', &errout);
644			out2str(sp->text);
645		}
646		for (sp = arglist.list ; sp ; sp = sp->next) {
647			outc(' ', &errout);
648			out2str(sp->text);
649		}
650		outc('\n', &errout);
651		flushout(&errout);
652	}
653
654	/* Now locate the command. */
655	if (argc == 0) {
656		cmdentry.cmdtype = CMDBUILTIN;
657		cmdentry.u.index = BLTINCMD;
658	} else {
659		static const char PATH[] = "PATH=";
660		char *path = pathval();
661
662		/*
663		 * Modify the command lookup path, if a PATH= assignment
664		 * is present
665		 */
666		for (sp = varlist.list ; sp ; sp = sp->next)
667			if (strncmp(sp->text, PATH, sizeof(PATH) - 1) == 0) {
668				path = sp->text + sizeof(PATH) - 1;
669				/*
670				 * On `PATH=... command`, we need to make
671				 * sure that the command isn't using the
672				 * non-updated hash table of the outer PATH
673				 * setting and we need to make sure that
674				 * the hash table isn't filled with items
675				 * from the temporary setting.
676				 *
677				 * It would be better to forbit using and
678				 * updating the table while this command
679				 * runs, by the command finding mechanism
680				 * is heavily integrated with hash handling,
681				 * so we just delete the hash before and after
682				 * the command runs. Partly deleting like
683				 * changepatch() does doesn't seem worth the
684				 * bookinging effort, since most such runs add
685				 * directories in front of the new PATH.
686				 */
687				clearcmdentry(0);
688				do_clearcmdentry = 1;
689			}
690
691		find_command(argv[0], &cmdentry, 1, path);
692		if (cmdentry.cmdtype == CMDUNKNOWN) {	/* command not found */
693			exitstatus = 127;
694			flushout(&errout);
695			return;
696		}
697		/* implement the bltin builtin here */
698		if (cmdentry.cmdtype == CMDBUILTIN && cmdentry.u.index == BLTINCMD) {
699			for (;;) {
700				argv++;
701				if (--argc == 0)
702					break;
703				if ((cmdentry.u.index = find_builtin(*argv)) < 0) {
704					outfmt(&errout, "%s: not found\n", *argv);
705					exitstatus = 127;
706					flushout(&errout);
707					return;
708				}
709				if (cmdentry.u.index != BLTINCMD)
710					break;
711			}
712		}
713	}
714
715	/* Fork off a child process if necessary. */
716	if (cmd->ncmd.backgnd
717	 || (cmdentry.cmdtype == CMDNORMAL
718	    && ((flags & EV_EXIT) == 0 || Tflag))
719	 || ((flags & EV_BACKCMD) != 0
720	    && (cmdentry.cmdtype != CMDBUILTIN
721		 || cmdentry.u.index == CDCMD
722		 || cmdentry.u.index == DOTCMD
723		 || cmdentry.u.index == EVALCMD))
724	 || (cmdentry.cmdtype == CMDBUILTIN &&
725	    cmdentry.u.index == COMMANDCMD)) {
726		jp = makejob(cmd, 1);
727		mode = cmd->ncmd.backgnd;
728		if (flags & EV_BACKCMD) {
729			mode = FORK_NOJOB;
730			if (pipe(pip) < 0)
731				error("Pipe call failed: %s", strerror(errno));
732		}
733		if (forkshell(jp, cmd, mode) != 0)
734			goto parent;	/* at end of routine */
735		if (flags & EV_BACKCMD) {
736			FORCEINTON;
737			close(pip[0]);
738			if (pip[1] != 1) {
739				dup2(pip[1], 1);
740				close(pip[1]);
741			}
742		}
743		flags |= EV_EXIT;
744	}
745
746	/* This is the child process if a fork occurred. */
747	/* Execute the command. */
748	if (cmdentry.cmdtype == CMDFUNCTION) {
749#ifdef DEBUG
750		trputs("Shell function:  ");  trargs(argv);
751#endif
752		redirect(cmd->ncmd.redirect, REDIR_PUSH);
753		saveparam = shellparam;
754		shellparam.malloc = 0;
755		shellparam.reset = 1;
756		shellparam.nparam = argc - 1;
757		shellparam.p = argv + 1;
758		shellparam.optnext = NULL;
759		INTOFF;
760		savelocalvars = localvars;
761		localvars = NULL;
762		INTON;
763		if (setjmp(jmploc.loc)) {
764			if (exception == EXSHELLPROC)
765				freeparam((struct shparam *)&saveparam);
766			else {
767				freeparam(&shellparam);
768				shellparam = saveparam;
769			}
770			poplocalvars();
771			localvars = savelocalvars;
772			handler = savehandler;
773			longjmp(handler->loc, 1);
774		}
775		savehandler = handler;
776		handler = &jmploc;
777		for (sp = varlist.list ; sp ; sp = sp->next)
778			mklocal(sp->text);
779		funcnest++;
780		if (flags & EV_TESTED)
781			evaltree(cmdentry.u.func, EV_TESTED);
782		else
783			evaltree(cmdentry.u.func, 0);
784		funcnest--;
785		INTOFF;
786		poplocalvars();
787		localvars = savelocalvars;
788		freeparam(&shellparam);
789		shellparam = saveparam;
790		handler = savehandler;
791		popredir();
792		INTON;
793		if (evalskip == SKIPFUNC) {
794			evalskip = 0;
795			skipcount = 0;
796		}
797		if (flags & EV_EXIT)
798			exitshell(exitstatus);
799	} else if (cmdentry.cmdtype == CMDBUILTIN) {
800#ifdef DEBUG
801		trputs("builtin command:  ");  trargs(argv);
802#endif
803		mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
804		if (flags == EV_BACKCMD) {
805			memout.nleft = 0;
806			memout.nextc = memout.buf;
807			memout.bufsize = 64;
808			mode |= REDIR_BACKQ;
809		}
810		redirect(cmd->ncmd.redirect, mode);
811		savecmdname = commandname;
812		cmdenviron = varlist.list;
813		e = -1;
814		if (setjmp(jmploc.loc)) {
815			e = exception;
816			exitstatus = (e == EXINT)? SIGINT+128 : 2;
817			goto cmddone;
818		}
819		savehandler = handler;
820		handler = &jmploc;
821		commandname = argv[0];
822		argptr = argv + 1;
823		optptr = NULL;			/* initialize nextopt */
824		exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
825		flushall();
826cmddone:
827		cmdenviron = NULL;
828		out1 = &output;
829		out2 = &errout;
830		freestdout();
831		if (e != EXSHELLPROC) {
832			commandname = savecmdname;
833			if (flags & EV_EXIT) {
834				exitshell(exitstatus);
835			}
836		}
837		handler = savehandler;
838		if (e != -1) {
839			if ((e != EXERROR && e != EXEXEC)
840			   || cmdentry.u.index == BLTINCMD
841			   || cmdentry.u.index == DOTCMD
842			   || cmdentry.u.index == EVALCMD
843#ifndef NO_HISTORY
844			   || cmdentry.u.index == HISTCMD
845#endif
846			   || cmdentry.u.index == EXECCMD
847			   || cmdentry.u.index == COMMANDCMD)
848				exraise(e);
849			FORCEINTON;
850		}
851		if (cmdentry.u.index != EXECCMD)
852			popredir();
853		if (flags == EV_BACKCMD) {
854			backcmd->buf = memout.buf;
855			backcmd->nleft = memout.nextc - memout.buf;
856			memout.buf = NULL;
857		}
858	} else {
859#ifdef DEBUG
860		trputs("normal command:  ");  trargs(argv);
861#endif
862		clearredir();
863		redirect(cmd->ncmd.redirect, 0);
864		for (sp = varlist.list ; sp ; sp = sp->next)
865			setvareq(sp->text, VEXPORT|VSTACK);
866		envp = environment();
867		shellexec(argv, envp, pathval(), cmdentry.u.index);
868		/*NOTREACHED*/
869	}
870	goto out;
871
872parent:	/* parent process gets here (if we forked) */
873	if (mode == 0) {	/* argument to fork */
874		INTOFF;
875		exitstatus = waitforjob(jp, &realstatus);
876		INTON;
877		if (iflag && loopnest > 0 && WIFSIGNALED(realstatus)) {
878			evalskip = SKIPBREAK;
879			skipcount = loopnest;
880		}
881	} else if (mode == 2) {
882		backcmd->fd = pip[0];
883		close(pip[1]);
884		backcmd->jp = jp;
885	}
886
887out:
888	if (lastarg)
889		setvar("_", lastarg, 0);
890	if (do_clearcmdentry)
891		clearcmdentry(0);
892	popstackmark(&smark);
893}
894
895
896
897/*
898 * Search for a command.  This is called before we fork so that the
899 * location of the command will be available in the parent as well as
900 * the child.  The check for "goodname" is an overly conservative
901 * check that the name will not be subject to expansion.
902 */
903
904STATIC void
905prehash(union node *n)
906{
907	struct cmdentry entry;
908
909	if (n->type == NCMD && n->ncmd.args)
910		if (goodname(n->ncmd.args->narg.text))
911			find_command(n->ncmd.args->narg.text, &entry, 0,
912				     pathval());
913}
914
915
916
917/*
918 * Builtin commands.  Builtin commands whose functions are closely
919 * tied to evaluation are implemented here.
920 */
921
922/*
923 * No command given, or a bltin command with no arguments.  Set the
924 * specified variables.
925 */
926
927int
928bltincmd(int argc __unused, char **argv __unused)
929{
930	listsetvar(cmdenviron);
931	/*
932	 * Preserve exitstatus of a previous possible redirection
933	 * as POSIX mandates
934	 */
935	return exitstatus;
936}
937
938
939/*
940 * Handle break and continue commands.  Break, continue, and return are
941 * all handled by setting the evalskip flag.  The evaluation routines
942 * above all check this flag, and if it is set they start skipping
943 * commands rather than executing them.  The variable skipcount is
944 * the number of loops to break/continue, or the number of function
945 * levels to return.  (The latter is always 1.)  It should probably
946 * be an error to break out of more loops than exist, but it isn't
947 * in the standard shell so we don't make it one here.
948 */
949
950int
951breakcmd(int argc, char **argv)
952{
953	int n = argc > 1 ? number(argv[1]) : 1;
954
955	if (n > loopnest)
956		n = loopnest;
957	if (n > 0) {
958		evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
959		skipcount = n;
960	}
961	return 0;
962}
963
964/*
965 * The `command' command.
966 */
967int
968commandcmd(int argc, char **argv)
969{
970	static char stdpath[] = _PATH_STDPATH;
971	struct jmploc loc, *old;
972	struct strlist *sp;
973	char *path;
974	int ch;
975
976	for (sp = cmdenviron; sp ; sp = sp->next)
977		setvareq(sp->text, VEXPORT|VSTACK);
978	path = pathval();
979
980	optind = optreset = 1;
981	opterr = 0;
982	while ((ch = getopt(argc, argv, "p")) != -1) {
983		switch (ch) {
984		case 'p':
985			path = stdpath;
986			break;
987		case '?':
988		default:
989			error("unknown option: -%c", optopt);
990		}
991	}
992	argc -= optind;
993	argv += optind;
994
995	if (argc != 0) {
996		old = handler;
997		handler = &loc;
998		if (setjmp(handler->loc) == 0)
999			shellexec(argv, environment(), path, 0);
1000		handler = old;
1001		if (exception == EXEXEC)
1002			exit(exerrno);
1003		exraise(exception);
1004	}
1005
1006	/*
1007	 * Do nothing successfully if no command was specified;
1008	 * ksh also does this.
1009	 */
1010	exit(0);
1011}
1012
1013
1014/*
1015 * The return command.
1016 */
1017
1018int
1019returncmd(int argc, char **argv)
1020{
1021	int ret = argc > 1 ? number(argv[1]) : oexitstatus;
1022
1023	if (funcnest) {
1024		evalskip = SKIPFUNC;
1025		skipcount = 1;
1026	} else {
1027		/* skip the rest of the file */
1028		evalskip = SKIPFILE;
1029		skipcount = 1;
1030	}
1031	return ret;
1032}
1033
1034
1035int
1036falsecmd(int argc __unused, char **argv __unused)
1037{
1038	return 1;
1039}
1040
1041
1042int
1043truecmd(int argc __unused, char **argv __unused)
1044{
1045	return 0;
1046}
1047
1048
1049int
1050execcmd(int argc, char **argv)
1051{
1052	if (argc > 1) {
1053		struct strlist *sp;
1054
1055		iflag = 0;		/* exit on error */
1056		mflag = 0;
1057		optschanged();
1058		for (sp = cmdenviron; sp ; sp = sp->next)
1059			setvareq(sp->text, VEXPORT|VSTACK);
1060		shellexec(argv + 1, environment(), pathval(), 0);
1061
1062	}
1063	return 0;
1064}
1065