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eval.c revision 1.13 
      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 1.13 1994/06/12 02:31:28 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 		if (redir->type == NFROM
    438 		 || redir->type == NTO
    439 		 || redir->type == NAPPEND) {
    440 			struct arglist fn;
    441 			fn.lastp = &fn.list;
    442 			expandarg(redir->nfile.fname, &fn, EXP_TILDE | EXP_REDIR);
    443 			redir->nfile.expfname = fn.list->text;
    444 		}
    445 	}
    446 }
    447 
    448 
    449 
    450 /*
    451  * Evaluate a pipeline.  All the processes in the pipeline are children
    452  * of the process creating the pipeline.  (This differs from some versions
    453  * of the shell, which make the last process in a pipeline the parent
    454  * of all the rest.)
    455  */
    456 
    457 STATIC void
    458 evalpipe(n)
    459 	union node *n;
    460 	{
    461 	struct job *jp;
    462 	struct nodelist *lp;
    463 	int pipelen;
    464 	int prevfd;
    465 	int pip[2];
    466 
    467 	TRACE(("evalpipe(0x%x) called\n", (int)n));
    468 	pipelen = 0;
    469 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
    470 		pipelen++;
    471 	INTOFF;
    472 	jp = makejob(n, pipelen);
    473 	prevfd = -1;
    474 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
    475 		prehash(lp->n);
    476 		pip[1] = -1;
    477 		if (lp->next) {
    478 			if (pipe(pip) < 0) {
    479 				close(prevfd);
    480 				error("Pipe call failed");
    481 			}
    482 		}
    483 		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
    484 			INTON;
    485 			if (prevfd > 0) {
    486 				close(0);
    487 				copyfd(prevfd, 0);
    488 				close(prevfd);
    489 			}
    490 			if (pip[1] >= 0) {
    491 				close(pip[0]);
    492 				if (pip[1] != 1) {
    493 					close(1);
    494 					copyfd(pip[1], 1);
    495 					close(pip[1]);
    496 				}
    497 			}
    498 			evaltree(lp->n, EV_EXIT);
    499 		}
    500 		if (prevfd >= 0)
    501 			close(prevfd);
    502 		prevfd = pip[0];
    503 		close(pip[1]);
    504 	}
    505 	INTON;
    506 	if (n->npipe.backgnd == 0) {
    507 		INTOFF;
    508 		exitstatus = waitforjob(jp);
    509 		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
    510 		INTON;
    511 	}
    512 }
    513 
    514 
    515 
    516 /*
    517  * Execute a command inside back quotes.  If it's a builtin command, we
    518  * want to save its output in a block obtained from malloc.  Otherwise
    519  * we fork off a subprocess and get the output of the command via a pipe.
    520  * Should be called with interrupts off.
    521  */
    522 
    523 void
    524 evalbackcmd(n, result)
    525 	union node *n;
    526 	struct backcmd *result;
    527 	{
    528 	int pip[2];
    529 	struct job *jp;
    530 	struct stackmark smark;		/* unnecessary */
    531 
    532 	setstackmark(&smark);
    533 	result->fd = -1;
    534 	result->buf = NULL;
    535 	result->nleft = 0;
    536 	result->jp = NULL;
    537 	exitstatus = 0;
    538 	if (n == NULL)
    539 		goto out;
    540 	if (n->type == NCMD) {
    541 		evalcommand(n, EV_BACKCMD, result);
    542 	} else {
    543 		if (pipe(pip) < 0)
    544 			error("Pipe call failed");
    545 		jp = makejob(n, 1);
    546 		if (forkshell(jp, n, FORK_NOJOB) == 0) {
    547 			FORCEINTON;
    548 			close(pip[0]);
    549 			if (pip[1] != 1) {
    550 				close(1);
    551 				copyfd(pip[1], 1);
    552 				close(pip[1]);
    553 			}
    554 			evaltree(n, EV_EXIT);
    555 		}
    556 		close(pip[1]);
    557 		result->fd = pip[0];
    558 		result->jp = jp;
    559 	}
    560 out:
    561 	popstackmark(&smark);
    562 	TRACE(("evalbackcmd done: fd=%d buf=0x%x nleft=%d jp=0x%x\n",
    563 		result->fd, result->buf, result->nleft, result->jp));
    564 }
    565 
    566 
    567 
    568 /*
    569  * Execute a simple command.
    570  */
    571 
    572 STATIC void
    573 evalcommand(cmd, flags, backcmd)
    574 	union node *cmd;
    575 	struct backcmd *backcmd;
    576 	{
    577 	struct stackmark smark;
    578 	union node *argp;
    579 	struct arglist arglist;
    580 	struct arglist varlist;
    581 	char **argv;
    582 	int argc;
    583 	char **envp;
    584 	int varflag;
    585 	struct strlist *sp;
    586 	register char *p;
    587 	int mode;
    588 	int pip[2];
    589 	struct cmdentry cmdentry;
    590 	struct job *jp;
    591 	struct jmploc jmploc;
    592 	struct jmploc *volatile savehandler;
    593 	char *volatile savecmdname;
    594 	volatile struct shparam saveparam;
    595 	struct localvar *volatile savelocalvars;
    596 	volatile int e;
    597 	char *lastarg;
    598 
    599 	/* First expand the arguments. */
    600 	TRACE(("evalcommand(0x%x, %d) called\n", (int)cmd, flags));
    601 	setstackmark(&smark);
    602 	arglist.lastp = &arglist.list;
    603 	varlist.lastp = &varlist.list;
    604 	varflag = 1;
    605 	for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
    606 		p = argp->narg.text;
    607 		if (varflag && is_name(*p)) {
    608 			do {
    609 				p++;
    610 			} while (is_in_name(*p));
    611 			if (*p == '=') {
    612 				expandarg(argp, &varlist, EXP_VARTILDE);
    613 				continue;
    614 			}
    615 		}
    616 		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
    617 		varflag = 0;
    618 	}
    619 	*arglist.lastp = NULL;
    620 	*varlist.lastp = NULL;
    621 	expredir(cmd->ncmd.redirect);
    622 	argc = 0;
    623 	for (sp = arglist.list ; sp ; sp = sp->next)
    624 		argc++;
    625 	argv = stalloc(sizeof (char *) * (argc + 1));
    626 
    627 	for (sp = arglist.list ; sp ; sp = sp->next) {
    628 		TRACE(("evalcommand arg: %s\n", sp->text));
    629 		*argv++ = sp->text;
    630 	}
    631 	*argv = NULL;
    632 	lastarg = NULL;
    633 	if (iflag && funcnest == 0 && argc > 0)
    634 		lastarg = argv[-1];
    635 	argv -= argc;
    636 
    637 	/* Print the command if xflag is set. */
    638 	if (xflag) {
    639 		outc('+', &errout);
    640 		for (sp = varlist.list ; sp ; sp = sp->next) {
    641 			outc(' ', &errout);
    642 			out2str(sp->text);
    643 		}
    644 		for (sp = arglist.list ; sp ; sp = sp->next) {
    645 			outc(' ', &errout);
    646 			out2str(sp->text);
    647 		}
    648 		outc('\n', &errout);
    649 		flushout(&errout);
    650 	}
    651 
    652 	/* Now locate the command. */
    653 	if (argc == 0) {
    654 		cmdentry.cmdtype = CMDBUILTIN;
    655 		cmdentry.u.index = BLTINCMD;
    656 	} else {
    657 		find_command(argv[0], &cmdentry, 1);
    658 		if (cmdentry.cmdtype == CMDUNKNOWN) {	/* command not found */
    659 			exitstatus = 2;
    660 			flushout(&errout);
    661 			return;
    662 		}
    663 		/* implement the bltin builtin here */
    664 		if (cmdentry.cmdtype == CMDBUILTIN && cmdentry.u.index == BLTINCMD) {
    665 			for (;;) {
    666 				argv++;
    667 				if (--argc == 0)
    668 					break;
    669 				if ((cmdentry.u.index = find_builtin(*argv)) < 0) {
    670 					outfmt(&errout, "%s: not found\n", *argv);
    671 					exitstatus = 2;
    672 					flushout(&errout);
    673 					return;
    674 				}
    675 				if (cmdentry.u.index != BLTINCMD)
    676 					break;
    677 			}
    678 		}
    679 	}
    680 
    681 	/* Fork off a child process if necessary. */
    682 	if (cmd->ncmd.backgnd
    683 	 || cmdentry.cmdtype == CMDNORMAL && (flags & EV_EXIT) == 0
    684 	 || (flags & EV_BACKCMD) != 0
    685 	    && (cmdentry.cmdtype != CMDBUILTIN
    686 		 || cmdentry.u.index == DOTCMD
    687 		 || cmdentry.u.index == EVALCMD)) {
    688 		jp = makejob(cmd, 1);
    689 		mode = cmd->ncmd.backgnd;
    690 		if (flags & EV_BACKCMD) {
    691 			mode = FORK_NOJOB;
    692 			if (pipe(pip) < 0)
    693 				error("Pipe call failed");
    694 		}
    695 		if (forkshell(jp, cmd, mode) != 0)
    696 			goto parent;	/* at end of routine */
    697 		if (flags & EV_BACKCMD) {
    698 			FORCEINTON;
    699 			close(pip[0]);
    700 			if (pip[1] != 1) {
    701 				close(1);
    702 				copyfd(pip[1], 1);
    703 				close(pip[1]);
    704 			}
    705 		}
    706 		flags |= EV_EXIT;
    707 	}
    708 
    709 	/* This is the child process if a fork occurred. */
    710 	/* Execute the command. */
    711 	if (cmdentry.cmdtype == CMDFUNCTION) {
    712 		trputs("Shell function:  ");  trargs(argv);
    713 		redirect(cmd->ncmd.redirect, REDIR_PUSH);
    714 		saveparam = shellparam;
    715 		shellparam.malloc = 0;
    716 		shellparam.nparam = argc - 1;
    717 		shellparam.p = argv + 1;
    718 		shellparam.optnext = NULL;
    719 		INTOFF;
    720 		savelocalvars = localvars;
    721 		localvars = NULL;
    722 		INTON;
    723 		if (setjmp(jmploc.loc)) {
    724 			if (exception == EXSHELLPROC)
    725 				freeparam((struct shparam *)&saveparam);
    726 			else {
    727 				freeparam(&shellparam);
    728 				shellparam = saveparam;
    729 			}
    730 			poplocalvars();
    731 			localvars = savelocalvars;
    732 			handler = savehandler;
    733 			longjmp(handler->loc, 1);
    734 		}
    735 		savehandler = handler;
    736 		handler = &jmploc;
    737 		for (sp = varlist.list ; sp ; sp = sp->next)
    738 			mklocal(sp->text);
    739 		funcnest++;
    740 		evaltree(cmdentry.u.func, 0);
    741 		funcnest--;
    742 		INTOFF;
    743 		poplocalvars();
    744 		localvars = savelocalvars;
    745 		freeparam(&shellparam);
    746 		shellparam = saveparam;
    747 		handler = savehandler;
    748 		popredir();
    749 		INTON;
    750 		if (evalskip == SKIPFUNC) {
    751 			evalskip = 0;
    752 			skipcount = 0;
    753 		}
    754 		if (flags & EV_EXIT)
    755 			exitshell(exitstatus);
    756 	} else if (cmdentry.cmdtype == CMDBUILTIN) {
    757 		trputs("builtin command:  ");  trargs(argv);
    758 		mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
    759 		if (flags == EV_BACKCMD) {
    760 			memout.nleft = 0;
    761 			memout.nextc = memout.buf;
    762 			memout.bufsize = 64;
    763 			mode |= REDIR_BACKQ;
    764 		}
    765 		redirect(cmd->ncmd.redirect, mode);
    766 		savecmdname = commandname;
    767 		cmdenviron = varlist.list;
    768 		e = -1;
    769 		if (setjmp(jmploc.loc)) {
    770 			e = exception;
    771 			exitstatus = (e == EXINT)? SIGINT+128 : 2;
    772 			goto cmddone;
    773 		}
    774 		savehandler = handler;
    775 		handler = &jmploc;
    776 		commandname = argv[0];
    777 		argptr = argv + 1;
    778 		optptr = NULL;			/* initialize nextopt */
    779 		exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
    780 		flushall();
    781 cmddone:
    782 		out1 = &output;
    783 		out2 = &errout;
    784 		freestdout();
    785 		if (e != EXSHELLPROC) {
    786 			commandname = savecmdname;
    787 			if (flags & EV_EXIT) {
    788 				exitshell(exitstatus);
    789 			}
    790 		}
    791 		handler = savehandler;
    792 		if (e != -1) {
    793 			if (e != EXERROR || cmdentry.u.index == BLTINCMD
    794 					       || cmdentry.u.index == DOTCMD
    795 					       || cmdentry.u.index == EVALCMD
    796 #ifndef NO_HISTORY
    797 					       || cmdentry.u.index == HISTCMD
    798 #endif
    799 					       || cmdentry.u.index == EXECCMD)
    800 				exraise(e);
    801 			FORCEINTON;
    802 		}
    803 		if (cmdentry.u.index != EXECCMD)
    804 			popredir();
    805 		if (flags == EV_BACKCMD) {
    806 			backcmd->buf = memout.buf;
    807 			backcmd->nleft = memout.nextc - memout.buf;
    808 			memout.buf = NULL;
    809 		}
    810 	} else {
    811 		trputs("normal command:  ");  trargs(argv);
    812 		clearredir();
    813 		redirect(cmd->ncmd.redirect, 0);
    814 		if (varlist.list) {
    815 			p = stalloc(strlen(pathval()) + 1);
    816 			scopy(pathval(), p);
    817 		} else {
    818 			p = pathval();
    819 		}
    820 		for (sp = varlist.list ; sp ; sp = sp->next)
    821 			setvareq(sp->text, VEXPORT|VSTACK);
    822 		envp = environment();
    823 		shellexec(argv, envp, p, cmdentry.u.index);
    824 		/*NOTREACHED*/
    825 	}
    826 	goto out;
    827 
    828 parent:	/* parent process gets here (if we forked) */
    829 	if (mode == 0) {	/* argument to fork */
    830 		INTOFF;
    831 		exitstatus = waitforjob(jp);
    832 		INTON;
    833 	} else if (mode == 2) {
    834 		backcmd->fd = pip[0];
    835 		close(pip[1]);
    836 		backcmd->jp = jp;
    837 	}
    838 
    839 out:
    840 	if (lastarg)
    841 		setvar("_", lastarg, 0);
    842 	popstackmark(&smark);
    843 }
    844 
    845 
    846 
    847 /*
    848  * Search for a command.  This is called before we fork so that the
    849  * location of the command will be available in the parent as well as
    850  * the child.  The check for "goodname" is an overly conservative
    851  * check that the name will not be subject to expansion.
    852  */
    853 
    854 STATIC void
    855 prehash(n)
    856 	union node *n;
    857 	{
    858 	struct cmdentry entry;
    859 
    860 	if (n->type == NCMD && goodname(n->ncmd.args->narg.text))
    861 		find_command(n->ncmd.args->narg.text, &entry, 0);
    862 }
    863 
    864 
    865 
    866 /*
    867  * Builtin commands.  Builtin commands whose functions are closely
    868  * tied to evaluation are implemented here.
    869  */
    870 
    871 /*
    872  * No command given, or a bltin command with no arguments.  Set the
    873  * specified variables.
    874  */
    875 
    876 bltincmd(argc, argv)  char **argv; {
    877 	listsetvar(cmdenviron);
    878 	return 0;
    879 }
    880 
    881 
    882 /*
    883  * Handle break and continue commands.  Break, continue, and return are
    884  * all handled by setting the evalskip flag.  The evaluation routines
    885  * above all check this flag, and if it is set they start skipping
    886  * commands rather than executing them.  The variable skipcount is
    887  * the number of loops to break/continue, or the number of function
    888  * levels to return.  (The latter is always 1.)  It should probably
    889  * be an error to break out of more loops than exist, but it isn't
    890  * in the standard shell so we don't make it one here.
    891  */
    892 
    893 breakcmd(argc, argv)  char **argv; {
    894 	int n;
    895 
    896 	n = 1;
    897 	if (argc > 1)
    898 		n = number(argv[1]);
    899 	if (n > loopnest)
    900 		n = loopnest;
    901 	if (n > 0) {
    902 		evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
    903 		skipcount = n;
    904 	}
    905 	return 0;
    906 }
    907 
    908 
    909 /*
    910  * The return command.
    911  */
    912 
    913 returncmd(argc, argv)  char **argv; {
    914 	int ret;
    915 
    916 	ret = exitstatus;
    917 	if (argc > 1)
    918 		ret = number(argv[1]);
    919 	if (funcnest) {
    920 		evalskip = SKIPFUNC;
    921 		skipcount = 1;
    922 	}
    923 	return ret;
    924 }
    925 
    926 
    927 falsecmd(argc, argv)  char **argv; {
    928 	return 1;
    929 }
    930 
    931 
    932 truecmd(argc, argv)  char **argv; {
    933 	return 0;
    934 }
    935 
    936 
    937 execcmd(argc, argv)  char **argv; {
    938 	if (argc > 1) {
    939 		iflag = 0;		/* exit on error */
    940 		mflag = 0;
    941 		optschanged();
    942 		shellexec(argv + 1, environment(), pathval(), 0);
    943 
    944 	}
    945 	return 0;
    946 }
    947