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eval.c revision 1.10 
      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[] = "@(#)eval.c	8.1 (Berkeley) 5/31/93";
     39 #endif /* not lint */
     40 
     41 /*
     42  * Evaluate a command.
     43  */
     44 
     45 #include "shell.h"
     46 #include "nodes.h"
     47 #include "syntax.h"
     48 #include "expand.h"
     49 #include "parser.h"
     50 #include "jobs.h"
     51 #include "eval.h"
     52 #include "builtins.h"
     53 #include "options.h"
     54 #include "exec.h"
     55 #include "redir.h"
     56 #include "input.h"
     57 #include "output.h"
     58 #include "trap.h"
     59 #include "var.h"
     60 #include "memalloc.h"
     61 #include "error.h"
     62 #include "mystring.h"
     63 #include "myhistedit.h"
     64 #include <signal.h>
     65 #include <unistd.h>
     66 
     67 
     68 /* flags in argument to evaltree */
     69 #define EV_EXIT 01		/* exit after evaluating tree */
     70 #define EV_TESTED 02		/* exit status is checked; ignore -e flag */
     71 #define EV_BACKCMD 04		/* command executing within back quotes */
     72 
     73 
     74 /* reasons for skipping commands (see comment on breakcmd routine) */
     75 #define SKIPBREAK 1
     76 #define SKIPCONT 2
     77 #define SKIPFUNC 3
     78 
     79 MKINIT int evalskip;		/* set if we are skipping commands */
     80 STATIC int skipcount;		/* number of levels to skip */
     81 MKINIT int loopnest;		/* current loop nesting level */
     82 int funcnest;			/* depth of function calls */
     83 
     84 
     85 char *commandname;
     86 struct strlist *cmdenviron;
     87 int exitstatus;			/* exit status of last command */
     88 
     89 
     90 #ifdef __STDC__
     91 STATIC void evalloop(union node *);
     92 STATIC void evalfor(union node *);
     93 STATIC void evalcase(union node *, int);
     94 STATIC void evalsubshell(union node *, int);
     95 STATIC void expredir(union node *);
     96 STATIC void evalpipe(union node *);
     97 STATIC void evalcommand(union node *, int, struct backcmd *);
     98 STATIC void prehash(union node *);
     99 #else
    100 STATIC void evalloop();
    101 STATIC void evalfor();
    102 STATIC void evalcase();
    103 STATIC void evalsubshell();
    104 STATIC void expredir();
    105 STATIC void evalpipe();
    106 STATIC void evalcommand();
    107 STATIC void prehash();
    108 #endif
    109 
    110 
    111 
    112 /*
    113  * Called to reset things after an exception.
    114  */
    115 
    116 #ifdef mkinit
    117 INCLUDE "eval.h"
    118 
    119 RESET {
    120 	evalskip = 0;
    121 	loopnest = 0;
    122 	funcnest = 0;
    123 }
    124 
    125 SHELLPROC {
    126 	exitstatus = 0;
    127 }
    128 #endif
    129 
    130 
    131 
    132 /*
    133  * The eval commmand.
    134  */
    135 
    136 evalcmd(argc, argv)
    137 	char **argv;
    138 {
    139         char *p;
    140         char *concat;
    141         char **ap;
    142 
    143         if (argc > 1) {
    144                 p = argv[1];
    145                 if (argc > 2) {
    146                         STARTSTACKSTR(concat);
    147                         ap = argv + 2;
    148                         for (;;) {
    149                                 while (*p)
    150                                         STPUTC(*p++, concat);
    151                                 if ((p = *ap++) == NULL)
    152                                         break;
    153                                 STPUTC(' ', concat);
    154                         }
    155                         STPUTC('\0', concat);
    156                         p = grabstackstr(concat);
    157                 }
    158                 evalstring(p);
    159         }
    160         return exitstatus;
    161 }
    162 
    163 
    164 /*
    165  * Execute a command or commands contained in a string.
    166  */
    167 
    168 void
    169 evalstring(s)
    170 	char *s;
    171 	{
    172 	union node *n;
    173 	struct stackmark smark;
    174 
    175 	setstackmark(&smark);
    176 	setinputstring(s, 1);
    177 	while ((n = parsecmd(0)) != NEOF) {
    178 		evaltree(n, 0);
    179 		popstackmark(&smark);
    180 	}
    181 	popfile();
    182 	popstackmark(&smark);
    183 }
    184 
    185 
    186 
    187 /*
    188  * Evaluate a parse tree.  The value is left in the global variable
    189  * exitstatus.
    190  */
    191 
    192 void
    193 evaltree(n, flags)
    194 	union node *n;
    195 	{
    196 	if (n == NULL) {
    197 		TRACE(("evaltree(NULL) called\n"));
    198 		exitstatus = 0;
    199 		goto out;
    200 	}
    201 #ifndef NO_HISTORY
    202 	displayhist = 1;	/* show history substitutions done with fc */
    203 #endif
    204 	TRACE(("evaltree(0x%x: %d) called\n", (int)n, n->type));
    205 	switch (n->type) {
    206 	case NSEMI:
    207 		evaltree(n->nbinary.ch1, 0);
    208 		if (evalskip)
    209 			goto out;
    210 		evaltree(n->nbinary.ch2, flags);
    211 		break;
    212 	case NAND:
    213 		evaltree(n->nbinary.ch1, EV_TESTED);
    214 		if (evalskip || exitstatus != 0)
    215 			goto out;
    216 		evaltree(n->nbinary.ch2, flags);
    217 		break;
    218 	case NOR:
    219 		evaltree(n->nbinary.ch1, EV_TESTED);
    220 		if (evalskip || exitstatus == 0)
    221 			goto out;
    222 		evaltree(n->nbinary.ch2, flags);
    223 		break;
    224 	case NREDIR:
    225 		expredir(n->nredir.redirect);
    226 		redirect(n->nredir.redirect, REDIR_PUSH);
    227 		evaltree(n->nredir.n, flags);
    228 		popredir();
    229 		break;
    230 	case NSUBSHELL:
    231 		evalsubshell(n, flags);
    232 		break;
    233 	case NBACKGND:
    234 		evalsubshell(n, flags);
    235 		break;
    236 	case NIF: {
    237 		int status = 0;
    238 
    239 		evaltree(n->nif.test, EV_TESTED);
    240 		if (evalskip)
    241 			goto out;
    242 		if (exitstatus == 0) {
    243 			evaltree(n->nif.ifpart, flags);
    244 			status = exitstatus;
    245 		} else if (n->nif.elsepart) {
    246 			evaltree(n->nif.elsepart, flags);
    247 			status = exitstatus;
    248 		}
    249 		exitstatus = status;
    250 		break;
    251 	}
    252 	case NWHILE:
    253 	case NUNTIL:
    254 		evalloop(n);
    255 		break;
    256 	case NFOR:
    257 		evalfor(n);
    258 		break;
    259 	case NCASE:
    260 		evalcase(n, flags);
    261 		break;
    262 	case NDEFUN:
    263 		defun(n->narg.text, n->narg.next);
    264 		exitstatus = 0;
    265 		break;
    266 	case NNOT:
    267 		evaltree(n->nnot.com, EV_TESTED);
    268 		exitstatus = !exitstatus;
    269 		break;
    270 
    271 	case NPIPE:
    272 		evalpipe(n);
    273 		break;
    274 	case NCMD:
    275 		evalcommand(n, flags, (struct backcmd *)NULL);
    276 		break;
    277 	default:
    278 		out1fmt("Node type = %d\n", n->type);
    279 		flushout(&output);
    280 		break;
    281 	}
    282 out:
    283 	if (pendingsigs)
    284 		dotrap();
    285 	if ((flags & EV_EXIT) || (eflag && exitstatus && !(flags & EV_TESTED)))
    286 		exitshell(exitstatus);
    287 }
    288 
    289 
    290 STATIC void
    291 evalloop(n)
    292 	union node *n;
    293 	{
    294 	int status;
    295 
    296 	loopnest++;
    297 	status = 0;
    298 	for (;;) {
    299 		evaltree(n->nbinary.ch1, EV_TESTED);
    300 		if (evalskip) {
    301 skipping:	  if (evalskip == SKIPCONT && --skipcount <= 0) {
    302 				evalskip = 0;
    303 				continue;
    304 			}
    305 			if (evalskip == SKIPBREAK && --skipcount <= 0)
    306 				evalskip = 0;
    307 			break;
    308 		}
    309 		if (n->type == NWHILE) {
    310 			if (exitstatus != 0)
    311 				break;
    312 		} else {
    313 			if (exitstatus == 0)
    314 				break;
    315 		}
    316 		evaltree(n->nbinary.ch2, 0);
    317 		status = exitstatus;
    318 		if (evalskip)
    319 			goto skipping;
    320 	}
    321 	loopnest--;
    322 	exitstatus = status;
    323 }
    324 
    325 
    326 
    327 STATIC void
    328 evalfor(n)
    329 	union node *n;
    330 	{
    331 	struct arglist arglist;
    332 	union node *argp;
    333 	struct strlist *sp;
    334 	struct stackmark smark;
    335 
    336 	setstackmark(&smark);
    337 	arglist.lastp = &arglist.list;
    338 	for (argp = n->nfor.args ; argp ; argp = argp->narg.next) {
    339 		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
    340 		if (evalskip)
    341 			goto out;
    342 	}
    343 	*arglist.lastp = NULL;
    344 
    345 	exitstatus = 0;
    346 	loopnest++;
    347 	for (sp = arglist.list ; sp ; sp = sp->next) {
    348 		setvar(n->nfor.var, sp->text, 0);
    349 		evaltree(n->nfor.body, 0);
    350 		if (evalskip) {
    351 			if (evalskip == SKIPCONT && --skipcount <= 0) {
    352 				evalskip = 0;
    353 				continue;
    354 			}
    355 			if (evalskip == SKIPBREAK && --skipcount <= 0)
    356 				evalskip = 0;
    357 			break;
    358 		}
    359 	}
    360 	loopnest--;
    361 out:
    362 	popstackmark(&smark);
    363 }
    364 
    365 
    366 
    367 STATIC void
    368 evalcase(n, flags)
    369 	union node *n;
    370 	{
    371 	union node *cp;
    372 	union node *patp;
    373 	struct arglist arglist;
    374 	struct stackmark smark;
    375 
    376 	setstackmark(&smark);
    377 	arglist.lastp = &arglist.list;
    378 	expandarg(n->ncase.expr, &arglist, EXP_TILDE);
    379 	for (cp = n->ncase.cases ; cp && evalskip == 0 ; cp = cp->nclist.next) {
    380 		for (patp = cp->nclist.pattern ; patp ; patp = patp->narg.next) {
    381 			if (casematch(patp, arglist.list->text)) {
    382 				if (evalskip == 0) {
    383 					evaltree(cp->nclist.body, flags);
    384 				}
    385 				goto out;
    386 			}
    387 		}
    388 	}
    389 out:
    390 	popstackmark(&smark);
    391 }
    392 
    393 
    394 
    395 /*
    396  * Kick off a subshell to evaluate a tree.
    397  */
    398 
    399 STATIC void
    400 evalsubshell(n, flags)
    401 	union node *n;
    402 	{
    403 	struct job *jp;
    404 	int backgnd = (n->type == NBACKGND);
    405 
    406 	expredir(n->nredir.redirect);
    407 	jp = makejob(n, 1);
    408 	if (forkshell(jp, n, backgnd) == 0) {
    409 		if (backgnd)
    410 			flags &=~ EV_TESTED;
    411 		redirect(n->nredir.redirect, 0);
    412 		evaltree(n->nredir.n, flags | EV_EXIT);	/* never returns */
    413 	}
    414 	if (! backgnd) {
    415 		INTOFF;
    416 		exitstatus = waitforjob(jp);
    417 		INTON;
    418 	}
    419 }
    420 
    421 
    422 
    423 /*
    424  * Compute the names of the files in a redirection list.
    425  */
    426 
    427 STATIC void
    428 expredir(n)
    429 	union node *n;
    430 	{
    431 	register union node *redir;
    432 
    433 	for (redir = n ; redir ; redir = redir->nfile.next) {
    434 		if (redir->type == NFROM
    435 		 || redir->type == NTO
    436 		 || redir->type == NAPPEND) {
    437 			struct arglist fn;
    438 			fn.lastp = &fn.list;
    439 			expandarg(redir->nfile.fname, &fn, EXP_TILDE | EXP_REDIR);
    440 			redir->nfile.expfname = fn.list->text;
    441 		}
    442 	}
    443 }
    444 
    445 
    446 
    447 /*
    448  * Evaluate a pipeline.  All the processes in the pipeline are children
    449  * of the process creating the pipeline.  (This differs from some versions
    450  * of the shell, which make the last process in a pipeline the parent
    451  * of all the rest.)
    452  */
    453 
    454 STATIC void
    455 evalpipe(n)
    456 	union node *n;
    457 	{
    458 	struct job *jp;
    459 	struct nodelist *lp;
    460 	int pipelen;
    461 	int prevfd;
    462 	int pip[2];
    463 
    464 	TRACE(("evalpipe(0x%x) called\n", (int)n));
    465 	pipelen = 0;
    466 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
    467 		pipelen++;
    468 	INTOFF;
    469 	jp = makejob(n, pipelen);
    470 	prevfd = -1;
    471 	for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
    472 		prehash(lp->n);
    473 		pip[1] = -1;
    474 		if (lp->next) {
    475 			if (pipe(pip) < 0) {
    476 				close(prevfd);
    477 				error("Pipe call failed");
    478 			}
    479 		}
    480 		if (forkshell(jp, lp->n, n->npipe.backgnd) == 0) {
    481 			INTON;
    482 			if (prevfd > 0) {
    483 				close(0);
    484 				copyfd(prevfd, 0);
    485 				close(prevfd);
    486 			}
    487 			if (pip[1] >= 0) {
    488 				close(pip[0]);
    489 				if (pip[1] != 1) {
    490 					close(1);
    491 					copyfd(pip[1], 1);
    492 					close(pip[1]);
    493 				}
    494 			}
    495 			evaltree(lp->n, EV_EXIT);
    496 		}
    497 		if (prevfd >= 0)
    498 			close(prevfd);
    499 		prevfd = pip[0];
    500 		close(pip[1]);
    501 	}
    502 	INTON;
    503 	if (n->npipe.backgnd == 0) {
    504 		INTOFF;
    505 		exitstatus = waitforjob(jp);
    506 		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
    507 		INTON;
    508 	}
    509 }
    510 
    511 
    512 
    513 /*
    514  * Execute a command inside back quotes.  If it's a builtin command, we
    515  * want to save its output in a block obtained from malloc.  Otherwise
    516  * we fork off a subprocess and get the output of the command via a pipe.
    517  * Should be called with interrupts off.
    518  */
    519 
    520 void
    521 evalbackcmd(n, result)
    522 	union node *n;
    523 	struct backcmd *result;
    524 	{
    525 	int pip[2];
    526 	struct job *jp;
    527 	struct stackmark smark;		/* unnecessary */
    528 
    529 	setstackmark(&smark);
    530 	result->fd = -1;
    531 	result->buf = NULL;
    532 	result->nleft = 0;
    533 	result->jp = NULL;
    534 	exitstatus = 0;
    535 	if (n == NULL)
    536 		goto out;
    537 	if (n->type == NCMD) {
    538 		evalcommand(n, EV_BACKCMD, result);
    539 	} else {
    540 		if (pipe(pip) < 0)
    541 			error("Pipe call failed");
    542 		jp = makejob(n, 1);
    543 		if (forkshell(jp, n, FORK_NOJOB) == 0) {
    544 			FORCEINTON;
    545 			close(pip[0]);
    546 			if (pip[1] != 1) {
    547 				close(1);
    548 				copyfd(pip[1], 1);
    549 				close(pip[1]);
    550 			}
    551 			evaltree(n, EV_EXIT);
    552 		}
    553 		close(pip[1]);
    554 		result->fd = pip[0];
    555 		result->jp = jp;
    556 	}
    557 out:
    558 	popstackmark(&smark);
    559 	TRACE(("evalbackcmd done: fd=%d buf=0x%x nleft=%d jp=0x%x\n",
    560 		result->fd, result->buf, result->nleft, result->jp));
    561 }
    562 
    563 
    564 
    565 /*
    566  * Execute a simple command.
    567  */
    568 
    569 STATIC void
    570 evalcommand(cmd, flags, backcmd)
    571 	union node *cmd;
    572 	struct backcmd *backcmd;
    573 	{
    574 	struct stackmark smark;
    575 	union node *argp;
    576 	struct arglist arglist;
    577 	struct arglist varlist;
    578 	char **argv;
    579 	int argc;
    580 	char **envp;
    581 	int varflag;
    582 	struct strlist *sp;
    583 	register char *p;
    584 	int mode;
    585 	int pip[2];
    586 	struct cmdentry cmdentry;
    587 	struct job *jp;
    588 	struct jmploc jmploc;
    589 	struct jmploc *volatile savehandler;
    590 	char *volatile savecmdname;
    591 	volatile struct shparam saveparam;
    592 	struct localvar *volatile savelocalvars;
    593 	volatile int e;
    594 	char *lastarg;
    595 
    596 	/* First expand the arguments. */
    597 	TRACE(("evalcommand(0x%x, %d) called\n", (int)cmd, flags));
    598 	setstackmark(&smark);
    599 	arglist.lastp = &arglist.list;
    600 	varlist.lastp = &varlist.list;
    601 	varflag = 1;
    602 	for (argp = cmd->ncmd.args ; argp ; argp = argp->narg.next) {
    603 		p = argp->narg.text;
    604 		if (varflag && is_name(*p)) {
    605 			do {
    606 				p++;
    607 			} while (is_in_name(*p));
    608 			if (*p == '=') {
    609 				expandarg(argp, &varlist, EXP_VARTILDE);
    610 				continue;
    611 			}
    612 		}
    613 		expandarg(argp, &arglist, EXP_FULL | EXP_TILDE);
    614 		varflag = 0;
    615 	}
    616 	*arglist.lastp = NULL;
    617 	*varlist.lastp = NULL;
    618 	expredir(cmd->ncmd.redirect);
    619 	argc = 0;
    620 	for (sp = arglist.list ; sp ; sp = sp->next)
    621 		argc++;
    622 	argv = stalloc(sizeof (char *) * (argc + 1));
    623 
    624 	for (sp = arglist.list ; sp ; sp = sp->next) {
    625 		TRACE(("evalcommand arg: %s\n", sp->text));
    626 		*argv++ = sp->text;
    627 	}
    628 	*argv = NULL;
    629 	lastarg = NULL;
    630 	if (iflag && funcnest == 0 && argc > 0)
    631 		lastarg = argv[-1];
    632 	argv -= argc;
    633 
    634 	/* Print the command if xflag is set. */
    635 	if (xflag) {
    636 		outc('+', &errout);
    637 		for (sp = varlist.list ; sp ; sp = sp->next) {
    638 			outc(' ', &errout);
    639 			out2str(sp->text);
    640 		}
    641 		for (sp = arglist.list ; sp ; sp = sp->next) {
    642 			outc(' ', &errout);
    643 			out2str(sp->text);
    644 		}
    645 		outc('\n', &errout);
    646 		flushout(&errout);
    647 	}
    648 
    649 	/* Now locate the command. */
    650 	if (argc == 0) {
    651 		cmdentry.cmdtype = CMDBUILTIN;
    652 		cmdentry.u.index = BLTINCMD;
    653 	} else {
    654 		find_command(argv[0], &cmdentry, 1);
    655 		if (cmdentry.cmdtype == CMDUNKNOWN) {	/* command not found */
    656 			exitstatus = 2;
    657 			flushout(&errout);
    658 			return;
    659 		}
    660 		/* implement the bltin builtin here */
    661 		if (cmdentry.cmdtype == CMDBUILTIN && cmdentry.u.index == BLTINCMD) {
    662 			for (;;) {
    663 				argv++;
    664 				if (--argc == 0)
    665 					break;
    666 				if ((cmdentry.u.index = find_builtin(*argv)) < 0) {
    667 					outfmt(&errout, "%s: not found\n", *argv);
    668 					exitstatus = 2;
    669 					flushout(&errout);
    670 					return;
    671 				}
    672 				if (cmdentry.u.index != BLTINCMD)
    673 					break;
    674 			}
    675 		}
    676 	}
    677 
    678 	/* Fork off a child process if necessary. */
    679 	if (cmd->ncmd.backgnd
    680 	 || cmdentry.cmdtype == CMDNORMAL && (flags & EV_EXIT) == 0
    681 	 || (flags & EV_BACKCMD) != 0
    682 	    && (cmdentry.cmdtype != CMDBUILTIN
    683 		 || cmdentry.u.index == DOTCMD
    684 		 || cmdentry.u.index == EVALCMD)) {
    685 		jp = makejob(cmd, 1);
    686 		mode = cmd->ncmd.backgnd;
    687 		if (flags & EV_BACKCMD) {
    688 			mode = FORK_NOJOB;
    689 			if (pipe(pip) < 0)
    690 				error("Pipe call failed");
    691 		}
    692 		if (forkshell(jp, cmd, mode) != 0)
    693 			goto parent;	/* at end of routine */
    694 		if (flags & EV_BACKCMD) {
    695 			FORCEINTON;
    696 			close(pip[0]);
    697 			if (pip[1] != 1) {
    698 				close(1);
    699 				copyfd(pip[1], 1);
    700 				close(pip[1]);
    701 			}
    702 		}
    703 		flags |= EV_EXIT;
    704 	}
    705 
    706 	/* This is the child process if a fork occurred. */
    707 	/* Execute the command. */
    708 	if (cmdentry.cmdtype == CMDFUNCTION) {
    709 		trputs("Shell function:  ");  trargs(argv);
    710 		redirect(cmd->ncmd.redirect, REDIR_PUSH);
    711 		saveparam = shellparam;
    712 		shellparam.malloc = 0;
    713 		shellparam.nparam = argc - 1;
    714 		shellparam.p = argv + 1;
    715 		shellparam.optnext = NULL;
    716 		INTOFF;
    717 		savelocalvars = localvars;
    718 		localvars = NULL;
    719 		INTON;
    720 		if (setjmp(jmploc.loc)) {
    721 			if (exception == EXSHELLPROC)
    722 				freeparam((struct shparam *)&saveparam);
    723 			else {
    724 				freeparam(&shellparam);
    725 				shellparam = saveparam;
    726 			}
    727 			poplocalvars();
    728 			localvars = savelocalvars;
    729 			handler = savehandler;
    730 			longjmp(handler->loc, 1);
    731 		}
    732 		savehandler = handler;
    733 		handler = &jmploc;
    734 		for (sp = varlist.list ; sp ; sp = sp->next)
    735 			mklocal(sp->text);
    736 		funcnest++;
    737 		evaltree(cmdentry.u.func, 0);
    738 		funcnest--;
    739 		INTOFF;
    740 		poplocalvars();
    741 		localvars = savelocalvars;
    742 		freeparam(&shellparam);
    743 		shellparam = saveparam;
    744 		handler = savehandler;
    745 		popredir();
    746 		INTON;
    747 		if (evalskip == SKIPFUNC) {
    748 			evalskip = 0;
    749 			skipcount = 0;
    750 		}
    751 		if (flags & EV_EXIT)
    752 			exitshell(exitstatus);
    753 	} else if (cmdentry.cmdtype == CMDBUILTIN) {
    754 		trputs("builtin command:  ");  trargs(argv);
    755 		mode = (cmdentry.u.index == EXECCMD)? 0 : REDIR_PUSH;
    756 		if (flags == EV_BACKCMD) {
    757 			memout.nleft = 0;
    758 			memout.nextc = memout.buf;
    759 			memout.bufsize = 64;
    760 			mode |= REDIR_BACKQ;
    761 		}
    762 		redirect(cmd->ncmd.redirect, mode);
    763 		savecmdname = commandname;
    764 		cmdenviron = varlist.list;
    765 		e = -1;
    766 		if (setjmp(jmploc.loc)) {
    767 			e = exception;
    768 			exitstatus = (e == EXINT)? SIGINT+128 : 2;
    769 			goto cmddone;
    770 		}
    771 		savehandler = handler;
    772 		handler = &jmploc;
    773 		commandname = argv[0];
    774 		argptr = argv + 1;
    775 		optptr = NULL;			/* initialize nextopt */
    776 		exitstatus = (*builtinfunc[cmdentry.u.index])(argc, argv);
    777 		flushall();
    778 cmddone:
    779 		out1 = &output;
    780 		out2 = &errout;
    781 		freestdout();
    782 		if (e != EXSHELLPROC) {
    783 			commandname = savecmdname;
    784 			if (flags & EV_EXIT) {
    785 				exitshell(exitstatus);
    786 			}
    787 		}
    788 		handler = savehandler;
    789 		if (e != -1) {
    790 			if (e != EXERROR || cmdentry.u.index == BLTINCMD
    791 					       || cmdentry.u.index == DOTCMD
    792 					       || cmdentry.u.index == EVALCMD
    793 #ifndef NO_HISTORY
    794 					       || cmdentry.u.index == HISTCMD
    795 #endif
    796 					       || cmdentry.u.index == EXECCMD)
    797 				exraise(e);
    798 			FORCEINTON;
    799 		}
    800 		if (cmdentry.u.index != EXECCMD)
    801 			popredir();
    802 		if (flags == EV_BACKCMD) {
    803 			backcmd->buf = memout.buf;
    804 			backcmd->nleft = memout.nextc - memout.buf;
    805 			memout.buf = NULL;
    806 		}
    807 	} else {
    808 		trputs("normal command:  ");  trargs(argv);
    809 		clearredir();
    810 		redirect(cmd->ncmd.redirect, 0);
    811 		if (varlist.list) {
    812 			p = stalloc(strlen(pathval()) + 1);
    813 			scopy(pathval(), p);
    814 		} else {
    815 			p = pathval();
    816 		}
    817 		for (sp = varlist.list ; sp ; sp = sp->next)
    818 			setvareq(sp->text, VEXPORT|VSTACK);
    819 		envp = environment();
    820 		shellexec(argv, envp, p, cmdentry.u.index);
    821 		/*NOTREACHED*/
    822 	}
    823 	goto out;
    824 
    825 parent:	/* parent process gets here (if we forked) */
    826 	if (mode == 0) {	/* argument to fork */
    827 		INTOFF;
    828 		exitstatus = waitforjob(jp);
    829 		INTON;
    830 	} else if (mode == 2) {
    831 		backcmd->fd = pip[0];
    832 		close(pip[1]);
    833 		backcmd->jp = jp;
    834 	}
    835 
    836 out:
    837 	if (lastarg)
    838 		setvar("_", lastarg, 0);
    839 	popstackmark(&smark);
    840 }
    841 
    842 
    843 
    844 /*
    845  * Search for a command.  This is called before we fork so that the
    846  * location of the command will be available in the parent as well as
    847  * the child.  The check for "goodname" is an overly conservative
    848  * check that the name will not be subject to expansion.
    849  */
    850 
    851 STATIC void
    852 prehash(n)
    853 	union node *n;
    854 	{
    855 	struct cmdentry entry;
    856 
    857 	if (n->type == NCMD && goodname(n->ncmd.args->narg.text))
    858 		find_command(n->ncmd.args->narg.text, &entry, 0);
    859 }
    860 
    861 
    862 
    863 /*
    864  * Builtin commands.  Builtin commands whose functions are closely
    865  * tied to evaluation are implemented here.
    866  */
    867 
    868 /*
    869  * No command given, or a bltin command with no arguments.  Set the
    870  * specified variables.
    871  */
    872 
    873 bltincmd(argc, argv)  char **argv; {
    874 	listsetvar(cmdenviron);
    875 	return exitstatus;
    876 }
    877 
    878 
    879 /*
    880  * Handle break and continue commands.  Break, continue, and return are
    881  * all handled by setting the evalskip flag.  The evaluation routines
    882  * above all check this flag, and if it is set they start skipping
    883  * commands rather than executing them.  The variable skipcount is
    884  * the number of loops to break/continue, or the number of function
    885  * levels to return.  (The latter is always 1.)  It should probably
    886  * be an error to break out of more loops than exist, but it isn't
    887  * in the standard shell so we don't make it one here.
    888  */
    889 
    890 breakcmd(argc, argv)  char **argv; {
    891 	int n;
    892 
    893 	n = 1;
    894 	if (argc > 1)
    895 		n = number(argv[1]);
    896 	if (n > loopnest)
    897 		n = loopnest;
    898 	if (n > 0) {
    899 		evalskip = (**argv == 'c')? SKIPCONT : SKIPBREAK;
    900 		skipcount = n;
    901 	}
    902 	return 0;
    903 }
    904 
    905 
    906 /*
    907  * The return command.
    908  */
    909 
    910 returncmd(argc, argv)  char **argv; {
    911 	int ret;
    912 
    913 	ret = exitstatus;
    914 	if (argc > 1)
    915 		ret = number(argv[1]);
    916 	if (funcnest) {
    917 		evalskip = SKIPFUNC;
    918 		skipcount = 1;
    919 	}
    920 	return ret;
    921 }
    922 
    923 
    924 falsecmd(argc, argv)  char **argv; {
    925 	return 1;
    926 }
    927 
    928 
    929 truecmd(argc, argv)  char **argv; {
    930 	return 0;
    931 }
    932 
    933 
    934 execcmd(argc, argv)  char **argv; {
    935 	if (argc > 1) {
    936 		iflag = 0;		/* exit on error */
    937 		mflag = 0;
    938 		optschanged();
    939 		shellexec(argv + 1, environment(), pathval(), 0);
    940 
    941 	}
    942 	return 0;
    943 }
    944