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eval.c revision 1.14 
      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  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #ifndef lint
     38 /*static char sccsid[] = "from: @(#)eval.c	8.1 (Berkeley) 5/31/93";*/
     39 static char *rcsid = "$Id: eval.c,v 1.14 1994/06/14 05:49:19 jtc Exp $";
     40 #endif /* not lint */
     41 
     42 /*
     43  * Evaluate a command.
     44  */
     45 
     46 #include "shell.h"
     47 #include "nodes.h"
     48 #include "syntax.h"
     49 #include "expand.h"
     50 #include "parser.h"
     51 #include "jobs.h"
     52 #include "eval.h"
     53 #include "builtins.h"
     54 #include "options.h"
     55 #include "exec.h"
     56 #include "redir.h"
     57 #include "input.h"
     58 #include "output.h"
     59 #include "trap.h"
     60 #include "var.h"
     61 #include "memalloc.h"
     62 #include "error.h"
     63 #include "mystring.h"
     64 #ifndef NO_HISTORY
     65 #include "myhistedit.h"
     66 #endif
     67 #include <signal.h>
     68 #include <unistd.h>
     69 
     70 
     71 /* flags in argument to evaltree */
     72 #define EV_EXIT 01		/* exit after evaluating tree */
     73 #define EV_TESTED 02		/* exit status is checked; ignore -e flag */
     74 #define EV_BACKCMD 04		/* command executing within back quotes */
     75 
     76 
     77 /* reasons for skipping commands (see comment on breakcmd routine) */
     78 #define SKIPBREAK 1
     79 #define SKIPCONT 2
     80 #define SKIPFUNC 3
     81 
     82 MKINIT int evalskip;		/* set if we are skipping commands */
     83 STATIC int skipcount;		/* number of levels to skip */
     84 MKINIT int loopnest;		/* current loop nesting level */
     85 int funcnest;			/* depth of function calls */
     86 
     87 
     88 char *commandname;
     89 struct strlist *cmdenviron;
     90 int exitstatus;			/* exit status of last command */
     91 
     92 
     93 #ifdef __STDC__
     94 STATIC void evalloop(union node *);
     95 STATIC void evalfor(union node *);
     96 STATIC void evalcase(union node *, int);
     97 STATIC void evalsubshell(union node *, int);
     98 STATIC void expredir(union node *);
     99 STATIC void evalpipe(union node *);
    100 STATIC void evalcommand(union node *, int, struct backcmd *);
    101 STATIC void prehash(union node *);
    102 #else
    103 STATIC void evalloop();
    104 STATIC void evalfor();
    105 STATIC void evalcase();
    106 STATIC void evalsubshell();
    107 STATIC void expredir();
    108 STATIC void evalpipe();
    109 STATIC void evalcommand();
    110 STATIC void prehash();
    111 #endif
    112 
    113 
    114 
    115 /*
    116  * Called to reset things after an exception.
    117  */
    118 
    119 #ifdef mkinit
    120 INCLUDE "eval.h"
    121 
    122 RESET {
    123 	evalskip = 0;
    124 	loopnest = 0;
    125 	funcnest = 0;
    126 }
    127 
    128 SHELLPROC {
    129 	exitstatus = 0;
    130 }
    131 #endif
    132 
    133 
    134 
    135 /*
    136  * The eval commmand.
    137  */
    138 
    139 evalcmd(argc, argv)
    140 	char **argv;
    141 {
    142         char *p;
    143         char *concat;
    144         char **ap;
    145 
    146         if (argc > 1) {
    147                 p = argv[1];
    148                 if (argc > 2) {
    149                         STARTSTACKSTR(concat);
    150                         ap = argv + 2;
    151                         for (;;) {
    152                                 while (*p)
    153                                         STPUTC(*p++, concat);
    154                                 if ((p = *ap++) == NULL)
    155                                         break;
    156                                 STPUTC(' ', concat);
    157                         }
    158                         STPUTC('\0', concat);
    159                         p = grabstackstr(concat);
    160                 }
    161                 evalstring(p);
    162         }
    163         return exitstatus;
    164 }
    165 
    166 
    167 /*
    168  * Execute a command or commands contained in a string.
    169  */
    170 
    171 void
    172 evalstring(s)
    173 	char *s;
    174 	{
    175 	union node *n;
    176 	struct stackmark smark;
    177 
    178 	setstackmark(&smark);
    179 	setinputstring(s, 1);
    180 	while ((n = parsecmd(0)) != NEOF) {
    181 		evaltree(n, 0);
    182 		popstackmark(&smark);
    183 	}
    184 	popfile();
    185 	popstackmark(&smark);
    186 }
    187 
    188 
    189 
    190 /*
    191  * Evaluate a parse tree.  The value is left in the global variable
    192  * exitstatus.
    193  */
    194 
    195 void
    196 evaltree(n, flags)
    197 	union node *n;
    198 	{
    199 	if (n == NULL) {
    200 		TRACE(("evaltree(NULL) called\n"));
    201 		exitstatus = 0;
    202 		goto out;
    203 	}
    204 #ifndef NO_HISTORY
    205 	displayhist = 1;	/* show history substitutions done with fc */
    206 #endif
    207 	TRACE(("evaltree(0x%x: %d) called\n", (int)n, n->type));
    208 	switch (n->type) {
    209 	case NSEMI:
    210 		evaltree(n->nbinary.ch1, 0);
    211 		if (evalskip)
    212 			goto out;
    213 		evaltree(n->nbinary.ch2, flags);
    214 		break;
    215 	case NAND:
    216 		evaltree(n->nbinary.ch1, EV_TESTED);
    217 		if (evalskip || exitstatus != 0)
    218 			goto out;
    219 		evaltree(n->nbinary.ch2, flags);
    220 		break;
    221 	case NOR:
    222 		evaltree(n->nbinary.ch1, EV_TESTED);
    223 		if (evalskip || exitstatus == 0)
    224 			goto out;
    225 		evaltree(n->nbinary.ch2, flags);
    226 		break;
    227 	case NREDIR:
    228 		expredir(n->nredir.redirect);
    229 		redirect(n->nredir.redirect, REDIR_PUSH);
    230 		evaltree(n->nredir.n, flags);
    231 		popredir();
    232 		break;
    233 	case NSUBSHELL:
    234 		evalsubshell(n, flags);
    235 		break;
    236 	case NBACKGND:
    237 		evalsubshell(n, flags);
    238 		break;
    239 	case NIF: {
    240 		int status = 0;
    241 
    242 		evaltree(n->nif.test, EV_TESTED);
    243 		if (evalskip)
    244 			goto out;
    245 		if (exitstatus == 0) {
    246 			evaltree(n->nif.ifpart, flags);
    247 			status = exitstatus;
    248 		} else if (n->nif.elsepart) {
    249 			evaltree(n->nif.elsepart, flags);
    250 			status = exitstatus;
    251 		}
    252 		exitstatus = status;
    253 		break;
    254 	}
    255 	case NWHILE:
    256 	case NUNTIL:
    257 		evalloop(n);
    258 		break;
    259 	case NFOR:
    260 		evalfor(n);
    261 		break;
    262 	case NCASE:
    263 		evalcase(n, flags);
    264 		break;
    265 	case NDEFUN:
    266 		defun(n->narg.text, n->narg.next);
    267 		exitstatus = 0;
    268 		break;
    269 	case NNOT:
    270 		evaltree(n->nnot.com, EV_TESTED);
    271 		exitstatus = !exitstatus;
    272 		break;
    273 
    274 	case NPIPE:
    275 		evalpipe(n);
    276 		break;
    277 	case NCMD:
    278 		evalcommand(n, flags, (struct backcmd *)NULL);
    279 		break;
    280 	default:
    281 		out1fmt("Node type = %d\n", n->type);
    282 		flushout(&output);
    283 		break;
    284 	}
    285 out:
    286 	if (pendingsigs)
    287 		dotrap();
    288 	if ((flags & EV_EXIT) || (eflag && exitstatus && !(flags & EV_TESTED)))
    289 		exitshell(exitstatus);
    290 }
    291 
    292 
    293 STATIC void
    294 evalloop(n)
    295 	union node *n;
    296 	{
    297 	int status;
    298 
    299 	loopnest++;
    300 	status = 0;
    301 	for (;;) {
    302 		evaltree(n->nbinary.ch1, EV_TESTED);
    303 		if (evalskip) {
    304 skipping:	  if (evalskip == SKIPCONT && --skipcount <= 0) {
    305 				evalskip = 0;
    306 				continue;
    307 			}
    308 			if (evalskip == SKIPBREAK && --skipcount <= 0)
    309 				evalskip = 0;
    310 			break;
    311 		}
    312 		if (n->type == NWHILE) {
    313 			if (exitstatus != 0)
    314 				break;
    315 		} else {
    316 			if (exitstatus == 0)
    317 				break;
    318 		}
    319 		evaltree(n->nbinary.ch2, 0);
    320 		status = exitstatus;
    321 		if (evalskip)
    322 			goto skipping;
    323 	}
    324 	loopnest--;
    325 	exitstatus = status;
    326 }
    327 
    328 
    329 
    330 STATIC void
    331 evalfor(n)
    332 	union node *n;
    333 	{
    334 	struct arglist arglist;
    335 	union node *argp;
    336 	struct strlist *sp;
    337 	struct stackmark smark;
    338 
    339 	setstackmark(&smark);
    340 	arglist.lastp = &arglist.list;
    341 	for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
    342 		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
    343 		if (evalskip)
    344 			goto out;
    345 	}
    346 	*arglist.lastp = NULL;
    347 
    348 	exitstatus = 0;
    349 	loopnest++;
    350 	for (sp = arglist.list ; sp ; sp = sp->next) {
    351 		setvar(n->nfor.var, sp->text, 0);
    352 		evaltree(n->nfor.body, 0);
    353 		if (evalskip) {
    354 			if (evalskip == SKIPCONT && --skipcount <= 0) {
    355 				evalskip = 0;
    356 				continue;
    357 			}
    358 			if (evalskip == SKIPBREAK && --skipcount <= 0)
    359 				evalskip = 0;
    360 			break;
    361 		}
    362 	}
    363 	loopnest--;
    364 out:
    365 	popstackmark(&smark);
    366 }
    367 
    368 
    369 
    370 STATIC void
    371 evalcase(n, flags)
    372 	union node *n;
    373 	{
    374 	union node *cp;
    375 	union node *patp;
    376 	struct arglist arglist;
    377 	struct stackmark smark;
    378 
    379 	setstackmark(&smark);
    380 	arglist.lastp = &arglist.list;
    381 	expandarg(n->ncase.expr, &arglist, EXP_TILDE);
    382 	for (cp = n->ncase.cases ; cp && evalskip == 0 ; cp = cp->nclist.next) {
    383 		for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
    384 			if (casematch(patp, arglist.list->text)) {
    385 				if (evalskip == 0) {
    386 					evaltree(cp->nclist.body, flags);
    387 				}
    388 				goto out;
    389 			}
    390 		}
    391 	}
    392 out:
    393 	popstackmark(&smark);
    394 }
    395 
    396 
    397 
    398 /*
    399  * Kick off a subshell to evaluate a tree.
    400  */
    401 
    402 STATIC void
    403 evalsubshell(n, flags)
    404 	union node *n;
    405 	{
    406 	struct job *jp;
    407 	int backgnd = (n->type == NBACKGND);
    408 
    409 	expredir(n->nredir.redirect);
    410 	jp = makejob(n, 1);
    411 	if (forkshell(jp, n, backgnd) == 0) {
    412 		if (backgnd)
    413 			flags &=~ EV_TESTED;
    414 		redirect(n->nredir.redirect, 0);
    415 		evaltree(n->nredir.n, flags | EV_EXIT);	/* never returns */
    416 	}
    417 	if (! backgnd) {
    418 		INTOFF;
    419 		exitstatus = waitforjob(jp);
    420 		INTON;
    421 	}
    422 }
    423 
    424 
    425 
    426 /*
    427  * Compute the names of the files in a redirection list.
    428  */
    429 
    430 STATIC void
    431 expredir(n)
    432 	union node *n;
    433 	{
    434 	register union node *redir;
    435 
    436 	for (redir = n ; redir ; redir = redir->nfile.next) {
    437 		struct arglist fn;
    438 		fn.lastp = &fn.list;
    439 		switch (redir->type) {
    440 		case NFROM:
    441 		case NTO:
    442 		case NAPPEND:
    443 			expandarg(redir->nfile.fname, &fn, EXP_TILDE | EXP_REDIR);
    444 			redir->nfile.expfname = fn.list->text;
    445 			break;
    446 		case NFROMFD:
    447 		case NTOFD:
    448 			if (redir->ndup.vname) {
    449 				expandarg(redir->ndup.vname, &fn, EXP_FULL | EXP_TILDE);
    450 				fixredir(redir, fn.list->text, 1);
    451 			}
    452 			break;
    453 		}
    454 	}
    455 }
    456 
    457 
    458 
    459 /*
    460  * Evaluate a pipeline.  All the processes in the pipeline are children
    461  * of the process creating the pipeline.  (This differs from some versions
    462  * of the shell, which make the last process in a pipeline the parent
    463  * of all the rest.)
    464  */
    465 
    466 STATIC void
    467 evalpipe(n)
    468 	union node *n;
    469 	{
    470 	struct job *jp;
    471 	struct nodelist *lp;
    472 	int pipelen;
    473 	int prevfd;
    474 	int pip[2];
    475 
    476 	TRACE(("evalpipe(0x%x) called\n", (int)n));
    477 	pipelen = 0;
    478 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
    479 		pipelen++;
    480 	INTOFF;
    481 	jp = makejob(n, pipelen);
    482 	prevfd = -1;
    483 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
    484 		prehash(lp->n);
    485 		pip[1] = -1;
    486 		if (lp->next) {
    487 			if (pipe(pip) < 0) {
    488 				close(prevfd);
    489 				error("Pipe call failed");
    490 			}
    491 		}
    492 		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
    493 			INTON;
    494 			if (prevfd > 0) {
    495 				close(0);
    496 				copyfd(prevfd, 0);
    497 				close(prevfd);
    498 			}
    499 			if (pip[1] >= 0) {
    500 				close(pip[0]);
    501 				if (pip[1] != 1) {
    502 					close(1);
    503 					copyfd(pip[1], 1);
    504 					close(pip[1]);
    505 				}
    506 			}
    507 			evaltree(lp->n, EV_EXIT);
    508 		}
    509 		if (prevfd >= 0)
    510 			close(prevfd);
    511 		prevfd = pip[0];
    512 		close(pip[1]);
    513 	}
    514 	INTON;
    515 	if (n->npipe.backgnd == 0) {
    516 		INTOFF;
    517 		exitstatus = waitforjob(jp);
    518 		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
    519 		INTON;
    520 	}
    521 }
    522 
    523 
    524 
    525 /*
    526  * Execute a command inside back quotes.  If it's a builtin command, we
    527  * want to save its output in a block obtained from malloc.  Otherwise
    528  * we fork off a subprocess and get the output of the command via a pipe.
    529  * Should be called with interrupts off.
    530  */
    531 
    532 void
    533 evalbackcmd(n, result)
    534 	union node *n;
    535 	struct backcmd *result;
    536 	{
    537 	int pip[2];
    538 	struct job *jp;
    539 	struct stackmark smark;		/* unnecessary */
    540 
    541 	setstackmark(&smark);
    542 	result->fd = -1;
    543 	result->buf = NULL;
    544 	result->nleft = 0;
    545 	result->jp = NULL;
    546 	exitstatus = 0;
    547 	if (n == NULL)
    548 		goto out;
    549 	if (n->type == NCMD) {
    550 		evalcommand(n, EV_BACKCMD, result);
    551 	} else {
    552 		if (pipe(pip) < 0)
    553 			error("Pipe call failed");
    554 		jp = makejob(n, 1);
    555 		if (forkshell(jp, n, FORK_NOJOB) == 0) {
    556 			FORCEINTON;
    557 			close(pip[0]);
    558 			if (pip[1] != 1) {
    559 				close(1);
    560 				copyfd(pip[1], 1);
    561 				close(pip[1]);
    562 			}
    563 			evaltree(n, EV_EXIT);
    564 		}
    565 		close(pip[1]);
    566 		result->fd = pip[0];
    567 		result->jp = jp;
    568 	}
    569 out:
    570 	popstackmark(&smark);
    571 	TRACE(("evalbackcmd done: fd=%d buf=0x%x nleft=%d jp=0x%x\n",
    572 		result->fd, result->buf, result->nleft, result->jp));
    573 }
    574 
    575 
    576 
    577 /*
    578  * Execute a simple command.
    579  */
    580 
    581 STATIC void
    582 evalcommand(cmd, flags, backcmd)
    583 	union node *cmd;
    584 	struct backcmd *backcmd;
    585 	{
    586 	struct stackmark smark;
    587 	union node *argp;
    588 	struct arglist arglist;
    589 	struct arglist varlist;
    590 	char **argv;
    591 	int argc;
    592 	char **envp;
    593 	int varflag;
    594 	struct strlist *sp;
    595 	register char *p;
    596 	int mode;
    597 	int pip[2];
    598 	struct cmdentry cmdentry;
    599 	struct job *jp;
    600 	struct jmploc jmploc;
    601 	struct jmploc *volatile savehandler;
    602 	char *volatile savecmdname;
    603 	volatile struct shparam saveparam;
    604 	struct localvar *volatile savelocalvars;
    605 	volatile int e;
    606 	char *lastarg;
    607 
    608 	/* First expand the arguments. */
    609 	TRACE(("evalcommand(0x%x, %d) called\n", (int)cmd, flags));
    610 	setstackmark(&smark);
    611 	arglist.lastp = &arglist.list;
    612 	varlist.lastp = &varlist.list;
    613 	varflag = 1;
    614 	for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
    615 		p = argp->narg.text;
    616 		if (varflag && is_name(*p)) {
    617 			do {
    618 				p++;
    619 			} while (is_in_name(*p));
    620 			if (*p == '=') {
    621 				expandarg(argp, &varlist, EXP_VARTILDE);
    622 				continue;
    623 			}
    624 		}
    625 		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
    626 		varflag = 0;
    627 	}
    628 	*arglist.lastp = NULL;
    629 	*varlist.lastp = NULL;
    630 	expredir(cmd->ncmd.redirect);
    631 	argc = 0;
    632 	for (sp = arglist.list ; sp ; sp = sp->next)
    633 		argc++;
    634 	argv = stalloc(sizeof (char *) * (argc + 1));
    635 
    636 	for (sp = arglist.list ; sp ; sp = sp->next) {
    637 		TRACE(("evalcommand arg: %s\n", sp->text));
    638 		*argv++ = sp->text;
    639 	}
    640 	*argv = NULL;
    641 	lastarg = NULL;
    642 	if (iflag && funcnest == 0 && argc > 0)
    643 		lastarg = argv[-1];
    644 	argv -= argc;
    645 
    646 	/* Print the command if xflag is set. */
    647 	if (xflag) {
    648 		outc('+', &errout);
    649 		for (sp = varlist.list ; sp ; sp = sp->next) {
    650 			outc(' ', &errout);
    651 			out2str(sp->text);
    652 		}
    653 		for (sp = arglist.list ; sp ; sp = sp->next) {
    654 			outc(' ', &errout);
    655 			out2str(sp->text);
    656 		}
    657 		outc('\n', &errout);
    658 		flushout(&errout);
    659 	}
    660 
    661 	/* Now locate the command. */
    662 	if (argc == 0) {
    663 		cmdentry.cmdtype = CMDBUILTIN;
    664 		cmdentry.u.index = BLTINCMD;
    665 	} else {
    666 		find_command(argv[0], &cmdentry, 1);
    667 		if (cmdentry.cmdtype == CMDUNKNOWN) {	/* command not found */
    668 			exitstatus = 2;
    669 			flushout(&errout);
    670 			return;
    671 		}
    672 		/* implement the bltin builtin here */
    673 		if (cmdentry.cmdtype == CMDBUILTIN && cmdentry.u.index == BLTINCMD) {
    674 			for (;;) {
    675 				argv++;
    676 				if (--argc == 0)
    677 					break;
    678 				if ((cmdentry.u.index = find_builtin(*argv)) < 0) {
    679 					outfmt(&errout, "%s: not found\n", *argv);
    680 					exitstatus = 2;
    681 					flushout(&errout);
    682 					return;
    683 				}
    684 				if (cmdentry.u.index != BLTINCMD)
    685 					break;
    686 			}
    687 		}
    688 	}
    689 
    690 	/* Fork off a child process if necessary. */
    691 	if (cmd->ncmd.backgnd
    692 	 || cmdentry.cmdtype == CMDNORMAL && (flags & EV_EXIT) == 0
    693 	 || (flags & EV_BACKCMD) != 0
    694 	    && (cmdentry.cmdtype != CMDBUILTIN
    695 		 || cmdentry.u.index == DOTCMD
    696 		 || cmdentry.u.index == EVALCMD)) {
    697 		jp = makejob(cmd, 1);
    698 		mode = cmd->ncmd.backgnd;
    699 		if (flags & EV_BACKCMD) {
    700 			mode = FORK_NOJOB;
    701 			if (pipe(pip) < 0)
    702 				error("Pipe call failed");
    703 		}
    704 		if (forkshell(jp, cmd, mode) != 0)
    705 			goto parent;	/* at end of routine */
    706 		if (flags & EV_BACKCMD) {
    707 			FORCEINTON;
    708 			close(pip[0]);
    709 			if (pip[1] != 1) {
    710 				close(1);
    711 				copyfd(pip[1], 1);
    712 				close(pip[1]);
    713 			}
    714 		}
    715 		flags |= EV_EXIT;
    716 	}
    717 
    718 	/* This is the child process if a fork occurred. */
    719 	/* Execute the command. */
    720 	if (cmdentry.cmdtype == CMDFUNCTION) {
    721 		trputs("Shell function:  ");  trargs(argv);
    722 		redirect(cmd->ncmd.redirect, REDIR_PUSH);
    723 		saveparam = shellparam;
    724 		shellparam.malloc = 0;
    725 		shellparam.nparam = argc - 1;
    726 		shellparam.p = argv + 1;
    727 		shellparam.optnext = NULL;
    728 		INTOFF;
    729 		savelocalvars = localvars;
    730 		localvars = NULL;
    731 		INTON;
    732 		if (setjmp(jmploc.loc)) {
    733 			if (exception == EXSHELLPROC)
    734 				freeparam((struct shparam *)&saveparam);
    735 			else {
    736 				freeparam(&shellparam);
    737 				shellparam = saveparam;
    738 			}
    739 			poplocalvars();
    740 			localvars = savelocalvars;
    741 			handler = savehandler;
    742 			longjmp(handler->loc, 1);
    743 		}
    744 		savehandler = handler;
    745 		handler = &jmploc;
    746 		for (sp = varlist.list ; sp ; sp = sp->next)
    747 			mklocal(sp->text);
    748 		funcnest++;
    749 		evaltree(cmdentry.u.func, 0);
    750 		funcnest--;
    751 		INTOFF;
    752 		poplocalvars();
    753 		localvars = savelocalvars;
    754 		freeparam(&shellparam);
    755 		shellparam = saveparam;
    756 		handler = savehandler;
    757 		popredir();
    758 		INTON;
    759 		if (evalskip == SKIPFUNC) {
    760 			evalskip = 0;
    761 			skipcount = 0;
    762 		}
    763 		if (flags & EV_EXIT)
    764 			exitshell(exitstatus);
    765 	} else if (cmdentry.cmdtype == CMDBUILTIN) {
    766 		trputs("builtin command:  ");  trargs(argv);
    767 		mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
    768 		if (flags == EV_BACKCMD) {
    769 			memout.nleft = 0;
    770 			memout.nextc = memout.buf;
    771 			memout.bufsize = 64;
    772 			mode |= REDIR_BACKQ;
    773 		}
    774 		redirect(cmd->ncmd.redirect, mode);
    775 		savecmdname = commandname;
    776 		cmdenviron = varlist.list;
    777 		e = -1;
    778 		if (setjmp(jmploc.loc)) {
    779 			e = exception;
    780 			exitstatus = (e == EXINT)? SIGINT+128 : 2;
    781 			goto cmddone;
    782 		}
    783 		savehandler = handler;
    784 		handler = &jmploc;
    785 		commandname = argv[0];
    786 		argptr = argv + 1;
    787 		optptr = NULL;			/* initialize nextopt */
    788 		exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
    789 		flushall();
    790 cmddone:
    791 		out1 = &output;
    792 		out2 = &errout;
    793 		freestdout();
    794 		if (e != EXSHELLPROC) {
    795 			commandname = savecmdname;
    796 			if (flags & EV_EXIT) {
    797 				exitshell(exitstatus);
    798 			}
    799 		}
    800 		handler = savehandler;
    801 		if (e != -1) {
    802 			if (e != EXERROR || cmdentry.u.index == BLTINCMD
    803 					       || cmdentry.u.index == DOTCMD
    804 					       || cmdentry.u.index == EVALCMD
    805 #ifndef NO_HISTORY
    806 					       || cmdentry.u.index == HISTCMD
    807 #endif
    808 					       || cmdentry.u.index == EXECCMD)
    809 				exraise(e);
    810 			FORCEINTON;
    811 		}
    812 		if (cmdentry.u.index != EXECCMD)
    813 			popredir();
    814 		if (flags == EV_BACKCMD) {
    815 			backcmd->buf = memout.buf;
    816 			backcmd->nleft = memout.nextc - memout.buf;
    817 			memout.buf = NULL;
    818 		}
    819 	} else {
    820 		trputs("normal command:  ");  trargs(argv);
    821 		clearredir();
    822 		redirect(cmd->ncmd.redirect, 0);
    823 		if (varlist.list) {
    824 			p = stalloc(strlen(pathval()) + 1);
    825 			scopy(pathval(), p);
    826 		} else {
    827 			p = pathval();
    828 		}
    829 		for (sp = varlist.list ; sp ; sp = sp->next)
    830 			setvareq(sp->text, VEXPORT|VSTACK);
    831 		envp = environment();
    832 		shellexec(argv, envp, p, cmdentry.u.index);
    833 		/*NOTREACHED*/
    834 	}
    835 	goto out;
    836 
    837 parent:	/* parent process gets here (if we forked) */
    838 	if (mode == 0) {	/* argument to fork */
    839 		INTOFF;
    840 		exitstatus = waitforjob(jp);
    841 		INTON;
    842 	} else if (mode == 2) {
    843 		backcmd->fd = pip[0];
    844 		close(pip[1]);
    845 		backcmd->jp = jp;
    846 	}
    847 
    848 out:
    849 	if (lastarg)
    850 		setvar("_", lastarg, 0);
    851 	popstackmark(&smark);
    852 }
    853 
    854 
    855 
    856 /*
    857  * Search for a command.  This is called before we fork so that the
    858  * location of the command will be available in the parent as well as
    859  * the child.  The check for "goodname" is an overly conservative
    860  * check that the name will not be subject to expansion.
    861  */
    862 
    863 STATIC void
    864 prehash(n)
    865 	union node *n;
    866 	{
    867 	struct cmdentry entry;
    868 
    869 	if (n->type == NCMD && goodname(n->ncmd.args->narg.text))
    870 		find_command(n->ncmd.args->narg.text, &entry, 0);
    871 }
    872 
    873 
    874 
    875 /*
    876  * Builtin commands.  Builtin commands whose functions are closely
    877  * tied to evaluation are implemented here.
    878  */
    879 
    880 /*
    881  * No command given, or a bltin command with no arguments.  Set the
    882  * specified variables.
    883  */
    884 
    885 bltincmd(argc, argv)  char **argv; {
    886 	listsetvar(cmdenviron);
    887 	return 0;
    888 }
    889 
    890 
    891 /*
    892  * Handle break and continue commands.  Break, continue, and return are
    893  * all handled by setting the evalskip flag.  The evaluation routines
    894  * above all check this flag, and if it is set they start skipping
    895  * commands rather than executing them.  The variable skipcount is
    896  * the number of loops to break/continue, or the number of function
    897  * levels to return.  (The latter is always 1.)  It should probably
    898  * be an error to break out of more loops than exist, but it isn't
    899  * in the standard shell so we don't make it one here.
    900  */
    901 
    902 breakcmd(argc, argv)  char **argv; {
    903 	int n;
    904 
    905 	n = 1;
    906 	if (argc > 1)
    907 		n = number(argv[1]);
    908 	if (n > loopnest)
    909 		n = loopnest;
    910 	if (n > 0) {
    911 		evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
    912 		skipcount = n;
    913 	}
    914 	return 0;
    915 }
    916 
    917 
    918 /*
    919  * The return command.
    920  */
    921 
    922 returncmd(argc, argv)  char **argv; {
    923 	int ret;
    924 
    925 	ret = exitstatus;
    926 	if (argc > 1)
    927 		ret = number(argv[1]);
    928 	if (funcnest) {
    929 		evalskip = SKIPFUNC;
    930 		skipcount = 1;
    931 	}
    932 	return ret;
    933 }
    934 
    935 
    936 falsecmd(argc, argv)  char **argv; {
    937 	return 1;
    938 }
    939 
    940 
    941 truecmd(argc, argv)  char **argv; {
    942 	return 0;
    943 }
    944 
    945 
    946 execcmd(argc, argv)  char **argv; {
    947 	if (argc > 1) {
    948 		iflag = 0;		/* exit on error */
    949 		mflag = 0;
    950 		optschanged();
    951 		shellexec(argv + 1, environment(), pathval(), 0);
    952 
    953 	}
    954 	return 0;
    955 }
    956