xref: /netbsd/bin/sh/exec.c (revision c4a72b64)
1 /*	$NetBSD: exec.c,v 1.34 2002/11/24 22:35:39 christos Exp $	*/
2 
3 /*-
4  * Copyright (c) 1991, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Kenneth Almquist.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #include <sys/cdefs.h>
40 #ifndef lint
41 #if 0
42 static char sccsid[] = "@(#)exec.c	8.4 (Berkeley) 6/8/95";
43 #else
44 __RCSID("$NetBSD: exec.c,v 1.34 2002/11/24 22:35:39 christos Exp $");
45 #endif
46 #endif /* not lint */
47 
48 #include <sys/types.h>
49 #include <sys/stat.h>
50 #include <sys/wait.h>
51 #include <unistd.h>
52 #include <fcntl.h>
53 #include <errno.h>
54 #include <stdio.h>
55 #include <stdlib.h>
56 
57 /*
58  * When commands are first encountered, they are entered in a hash table.
59  * This ensures that a full path search will not have to be done for them
60  * on each invocation.
61  *
62  * We should investigate converting to a linear search, even though that
63  * would make the command name "hash" a misnomer.
64  */
65 
66 #include "shell.h"
67 #include "main.h"
68 #include "nodes.h"
69 #include "parser.h"
70 #include "redir.h"
71 #include "eval.h"
72 #include "exec.h"
73 #include "builtins.h"
74 #include "var.h"
75 #include "options.h"
76 #include "input.h"
77 #include "output.h"
78 #include "syntax.h"
79 #include "memalloc.h"
80 #include "error.h"
81 #include "init.h"
82 #include "mystring.h"
83 #include "show.h"
84 #include "jobs.h"
85 #include "alias.h"
86 
87 
88 #define CMDTABLESIZE 31		/* should be prime */
89 #define ARB 1			/* actual size determined at run time */
90 
91 
92 
93 struct tblentry {
94 	struct tblentry *next;	/* next entry in hash chain */
95 	union param param;	/* definition of builtin function */
96 	short cmdtype;		/* index identifying command */
97 	char rehash;		/* if set, cd done since entry created */
98 	char cmdname[ARB];	/* name of command */
99 };
100 
101 
102 STATIC struct tblentry *cmdtable[CMDTABLESIZE];
103 STATIC int builtinloc = -1;		/* index in path of %builtin, or -1 */
104 int exerrno = 0;			/* Last exec error */
105 
106 
107 STATIC void tryexec(char *, char **, char **, int);
108 STATIC void execinterp(char **, char **);
109 STATIC void printentry(struct tblentry *, int);
110 STATIC void clearcmdentry(int);
111 STATIC struct tblentry *cmdlookup(const char *, int);
112 STATIC void delete_cmd_entry(void);
113 
114 
115 extern char *const parsekwd[];
116 
117 /*
118  * Exec a program.  Never returns.  If you change this routine, you may
119  * have to change the find_command routine as well.
120  */
121 
122 void
123 shellexec(char **argv, char **envp, const char *path, int idx, int vforked)
124 {
125 	char *cmdname;
126 	int e;
127 
128 	if (strchr(argv[0], '/') != NULL) {
129 		tryexec(argv[0], argv, envp, vforked);
130 		e = errno;
131 	} else {
132 		e = ENOENT;
133 		while ((cmdname = padvance(&path, argv[0])) != NULL) {
134 			if (--idx < 0 && pathopt == NULL) {
135 				tryexec(cmdname, argv, envp, vforked);
136 				if (errno != ENOENT && errno != ENOTDIR)
137 					e = errno;
138 			}
139 			stunalloc(cmdname);
140 		}
141 	}
142 
143 	/* Map to POSIX errors */
144 	switch (e) {
145 	case EACCES:
146 		exerrno = 126;
147 		break;
148 	case ENOENT:
149 		exerrno = 127;
150 		break;
151 	default:
152 		exerrno = 2;
153 		break;
154 	}
155 	TRACE(("shellexec failed for %s, errno %d, vforked %d, suppressint %d\n",
156 		argv[0], e, vforked, suppressint ));
157 	exerror(EXEXEC, "%s: %s", argv[0], errmsg(e, E_EXEC));
158 	/* NOTREACHED */
159 }
160 
161 
162 STATIC void
163 tryexec(char *cmd, char **argv, char **envp, int vforked)
164 {
165 	int e;
166 #ifndef BSD
167 	char *p;
168 #endif
169 
170 #ifdef SYSV
171 	do {
172 		execve(cmd, argv, envp);
173 	} while (errno == EINTR);
174 #else
175 	execve(cmd, argv, envp);
176 #endif
177 	e = errno;
178 	if (e == ENOEXEC) {
179 		if (vforked) {
180 			/* We are currently vfork(2)ed, so raise an
181 			 * exception, and evalcommand will try again
182 			 * with a normal fork(2).
183 			 */
184 			exraise(EXSHELLPROC);
185 		}
186 		initshellproc();
187 		setinputfile(cmd, 0);
188 		commandname = arg0 = savestr(argv[0]);
189 #ifndef BSD
190 		pgetc(); pungetc();		/* fill up input buffer */
191 		p = parsenextc;
192 		if (parsenleft > 2 && p[0] == '#' && p[1] == '!') {
193 			argv[0] = cmd;
194 			execinterp(argv, envp);
195 		}
196 #endif
197 		setparam(argv + 1);
198 		exraise(EXSHELLPROC);
199 	}
200 	errno = e;
201 }
202 
203 
204 #ifndef BSD
205 /*
206  * Execute an interpreter introduced by "#!", for systems where this
207  * feature has not been built into the kernel.  If the interpreter is
208  * the shell, return (effectively ignoring the "#!").  If the execution
209  * of the interpreter fails, exit.
210  *
211  * This code peeks inside the input buffer in order to avoid actually
212  * reading any input.  It would benefit from a rewrite.
213  */
214 
215 #define NEWARGS 5
216 
217 STATIC void
218 execinterp(char **argv, char **envp)
219 {
220 	int n;
221 	char *inp;
222 	char *outp;
223 	char c;
224 	char *p;
225 	char **ap;
226 	char *newargs[NEWARGS];
227 	int i;
228 	char **ap2;
229 	char **new;
230 
231 	n = parsenleft - 2;
232 	inp = parsenextc + 2;
233 	ap = newargs;
234 	for (;;) {
235 		while (--n >= 0 && (*inp == ' ' || *inp == '\t'))
236 			inp++;
237 		if (n < 0)
238 			goto bad;
239 		if ((c = *inp++) == '\n')
240 			break;
241 		if (ap == &newargs[NEWARGS])
242 bad:		  error("Bad #! line");
243 		STARTSTACKSTR(outp);
244 		do {
245 			STPUTC(c, outp);
246 		} while (--n >= 0 && (c = *inp++) != ' ' && c != '\t' && c != '\n');
247 		STPUTC('\0', outp);
248 		n++, inp--;
249 		*ap++ = grabstackstr(outp);
250 	}
251 	if (ap == newargs + 1) {	/* if no args, maybe no exec is needed */
252 		p = newargs[0];
253 		for (;;) {
254 			if (equal(p, "sh") || equal(p, "ash")) {
255 				return;
256 			}
257 			while (*p != '/') {
258 				if (*p == '\0')
259 					goto break2;
260 				p++;
261 			}
262 			p++;
263 		}
264 break2:;
265 	}
266 	i = (char *)ap - (char *)newargs;		/* size in bytes */
267 	if (i == 0)
268 		error("Bad #! line");
269 	for (ap2 = argv ; *ap2++ != NULL ; );
270 	new = ckmalloc(i + ((char *)ap2 - (char *)argv));
271 	ap = newargs, ap2 = new;
272 	while ((i -= sizeof (char **)) >= 0)
273 		*ap2++ = *ap++;
274 	ap = argv;
275 	while (*ap2++ = *ap++);
276 	shellexec(new, envp, pathval(), 0);
277 	/* NOTREACHED */
278 }
279 #endif
280 
281 
282 
283 /*
284  * Do a path search.  The variable path (passed by reference) should be
285  * set to the start of the path before the first call; padvance will update
286  * this value as it proceeds.  Successive calls to padvance will return
287  * the possible path expansions in sequence.  If an option (indicated by
288  * a percent sign) appears in the path entry then the global variable
289  * pathopt will be set to point to it; otherwise pathopt will be set to
290  * NULL.
291  */
292 
293 const char *pathopt;
294 
295 char *
296 padvance(const char **path, const char *name)
297 {
298 	const char *p;
299 	char *q;
300 	const char *start;
301 	int len;
302 
303 	if (*path == NULL)
304 		return NULL;
305 	start = *path;
306 	for (p = start ; *p && *p != ':' && *p != '%' ; p++);
307 	len = p - start + strlen(name) + 2;	/* "2" is for '/' and '\0' */
308 	while (stackblocksize() < len)
309 		growstackblock();
310 	q = stackblock();
311 	if (p != start) {
312 		memcpy(q, start, p - start);
313 		q += p - start;
314 		*q++ = '/';
315 	}
316 	strcpy(q, name);
317 	pathopt = NULL;
318 	if (*p == '%') {
319 		pathopt = ++p;
320 		while (*p && *p != ':')  p++;
321 	}
322 	if (*p == ':')
323 		*path = p + 1;
324 	else
325 		*path = NULL;
326 	return stalloc(len);
327 }
328 
329 
330 
331 /*** Command hashing code ***/
332 
333 
334 int
335 hashcmd(int argc, char **argv)
336 {
337 	struct tblentry **pp;
338 	struct tblentry *cmdp;
339 	int c;
340 	int verbose;
341 	struct cmdentry entry;
342 	char *name;
343 
344 	verbose = 0;
345 	while ((c = nextopt("rv")) != '\0') {
346 		if (c == 'r') {
347 			clearcmdentry(0);
348 		} else if (c == 'v') {
349 			verbose++;
350 		}
351 	}
352 	if (*argptr == NULL) {
353 		for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
354 			for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
355 				printentry(cmdp, verbose);
356 			}
357 		}
358 		return 0;
359 	}
360 	while ((name = *argptr) != NULL) {
361 		if ((cmdp = cmdlookup(name, 0)) != NULL
362 		 && (cmdp->cmdtype == CMDNORMAL
363 		     || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0)))
364 			delete_cmd_entry();
365 		find_command(name, &entry, DO_ERR, pathval());
366 		if (verbose) {
367 			if (entry.cmdtype != CMDUNKNOWN) {	/* if no error msg */
368 				cmdp = cmdlookup(name, 0);
369 				printentry(cmdp, verbose);
370 			}
371 			flushall();
372 		}
373 		argptr++;
374 	}
375 	return 0;
376 }
377 
378 
379 STATIC void
380 printentry(struct tblentry *cmdp, int verbose)
381 {
382 	int idx;
383 	const char *path;
384 	char *name;
385 
386 	switch (cmdp->cmdtype) {
387 	case CMDNORMAL:
388 		idx = cmdp->param.index;
389 		path = pathval();
390 		do {
391 			name = padvance(&path, cmdp->cmdname);
392 			stunalloc(name);
393 		} while (--idx >= 0);
394 		out1str(name);
395 		break;
396 	case CMDSPLBLTIN:
397 		out1fmt("special builtin %s", cmdp->cmdname);
398 		break;
399 	case CMDBUILTIN:
400 		out1fmt("builtin %s", cmdp->cmdname);
401 		break;
402 	case CMDFUNCTION:
403 		out1fmt("function %s", cmdp->cmdname);
404 		if (verbose) {
405 			struct procstat ps;
406 			INTOFF;
407 			commandtext(&ps, cmdp->param.func);
408 			out1c(' ');
409 			out1str(ps.cmd);
410 			INTON;
411 		}
412 		break;
413 	default:
414 		error("internal error: %s cmdtype %d", cmdp->cmdname, cmdp->cmdtype);
415 	}
416 	if (cmdp->rehash)
417 		out1c('*');
418 	out1c('\n');
419 }
420 
421 
422 
423 /*
424  * Resolve a command name.  If you change this routine, you may have to
425  * change the shellexec routine as well.
426  */
427 
428 void
429 find_command(char *name, struct cmdentry *entry, int act, const char *path)
430 {
431 	struct tblentry *cmdp;
432 	int idx;
433 	int prev;
434 	char *fullname;
435 	struct stat statb;
436 	int e;
437 	int (*bltin)(int,char **);
438 
439 	/* If name contains a slash, don't use the hash table */
440 	if (strchr(name, '/') != NULL) {
441 		if (act & DO_ABS) {
442 			while (stat(name, &statb) < 0) {
443 #ifdef SYSV
444 				if (errno == EINTR)
445 					continue;
446 #endif
447 				if (errno != ENOENT && errno != ENOTDIR)
448 					e = errno;
449 				entry->cmdtype = CMDUNKNOWN;
450 				entry->u.index = -1;
451 				return;
452 			}
453 			entry->cmdtype = CMDNORMAL;
454 			entry->u.index = -1;
455 			return;
456 		}
457 		entry->cmdtype = CMDNORMAL;
458 		entry->u.index = 0;
459 		return;
460 	}
461 
462 	/* If name is in the table, and not invalidated by cd, we're done */
463 	if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->rehash == 0)
464 		goto success;
465 
466 	/* If %builtin not in path, check for builtin next */
467 	if (builtinloc < 0 && (bltin = find_builtin(name)) != 0) {
468 		INTOFF;
469 		cmdp = cmdlookup(name, 1);
470 		cmdp->cmdtype = CMDBUILTIN;
471 		cmdp->param.bltin = bltin;
472 		INTON;
473 		goto success;
474 	}
475 
476 	/* We have to search path. */
477 	prev = -1;		/* where to start */
478 	if (cmdp) {		/* doing a rehash */
479 		if (cmdp->cmdtype == CMDBUILTIN)
480 			prev = builtinloc;
481 		else
482 			prev = cmdp->param.index;
483 	}
484 
485 	e = ENOENT;
486 	idx = -1;
487 loop:
488 	while ((fullname = padvance(&path, name)) != NULL) {
489 		stunalloc(fullname);
490 		idx++;
491 		if (pathopt) {
492 			if (prefix("builtin", pathopt)) {
493 				if ((bltin = find_builtin(name)) == 0)
494 					goto loop;
495 				INTOFF;
496 				cmdp = cmdlookup(name, 1);
497 				cmdp->cmdtype = CMDBUILTIN;
498 				cmdp->param.bltin = bltin;
499 				INTON;
500 				goto success;
501 			} else if (prefix("func", pathopt)) {
502 				/* handled below */
503 			} else {
504 				goto loop;	/* ignore unimplemented options */
505 			}
506 		}
507 		/* if rehash, don't redo absolute path names */
508 		if (fullname[0] == '/' && idx <= prev) {
509 			if (idx < prev)
510 				goto loop;
511 			TRACE(("searchexec \"%s\": no change\n", name));
512 			goto success;
513 		}
514 		while (stat(fullname, &statb) < 0) {
515 #ifdef SYSV
516 			if (errno == EINTR)
517 				continue;
518 #endif
519 			if (errno != ENOENT && errno != ENOTDIR)
520 				e = errno;
521 			goto loop;
522 		}
523 		e = EACCES;	/* if we fail, this will be the error */
524 		if (!S_ISREG(statb.st_mode))
525 			goto loop;
526 		if (pathopt) {		/* this is a %func directory */
527 			stalloc(strlen(fullname) + 1);
528 			readcmdfile(fullname);
529 			if ((cmdp = cmdlookup(name, 0)) == NULL || cmdp->cmdtype != CMDFUNCTION)
530 				error("%s not defined in %s", name, fullname);
531 			stunalloc(fullname);
532 			goto success;
533 		}
534 #ifdef notdef
535 		if (statb.st_uid == geteuid()) {
536 			if ((statb.st_mode & 0100) == 0)
537 				goto loop;
538 		} else if (statb.st_gid == getegid()) {
539 			if ((statb.st_mode & 010) == 0)
540 				goto loop;
541 		} else {
542 			if ((statb.st_mode & 01) == 0)
543 				goto loop;
544 		}
545 #endif
546 		TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
547 		INTOFF;
548 		cmdp = cmdlookup(name, 1);
549 		cmdp->cmdtype = CMDNORMAL;
550 		cmdp->param.index = idx;
551 		INTON;
552 		goto success;
553 	}
554 
555 	/* We failed.  If there was an entry for this command, delete it */
556 	if (cmdp)
557 		delete_cmd_entry();
558 	if (act & DO_ERR)
559 		outfmt(out2, "%s: %s\n", name, errmsg(e, E_EXEC));
560 	entry->cmdtype = CMDUNKNOWN;
561 	return;
562 
563 success:
564 	cmdp->rehash = 0;
565 	entry->cmdtype = cmdp->cmdtype;
566 	entry->u = cmdp->param;
567 }
568 
569 
570 
571 /*
572  * Search the table of builtin commands.
573  */
574 
575 int
576 (*find_builtin(name))(int, char **)
577 	char *name;
578 {
579 	const struct builtincmd *bp;
580 
581 	for (bp = builtincmd ; bp->name ; bp++) {
582 		if (*bp->name == *name && equal(bp->name, name))
583 			return bp->builtin;
584 	}
585 	return 0;
586 }
587 
588 int
589 (*find_splbltin(name))(int, char **)
590 	char *name;
591 {
592 	const struct builtincmd *bp;
593 
594 	for (bp = splbltincmd ; bp->name ; bp++) {
595 		if (*bp->name == *name && equal(bp->name, name))
596 			return bp->builtin;
597 	}
598 	return 0;
599 }
600 
601 /*
602  * At shell startup put special builtins into hash table.
603  * ensures they are executed first (see posix).
604  * We stop functions being added with the same name
605  * (as they are impossible to call)
606  */
607 
608 void
609 hash_special_builtins(void)
610 {
611 	const struct builtincmd *bp;
612 	struct tblentry *cmdp;
613 
614 	for (bp = splbltincmd ; bp->name ; bp++) {
615 		cmdp = cmdlookup(bp->name, 1);
616 		cmdp->cmdtype = CMDSPLBLTIN;
617 		cmdp->param.bltin = bp->builtin;
618 	}
619 }
620 
621 
622 
623 /*
624  * Called when a cd is done.  Marks all commands so the next time they
625  * are executed they will be rehashed.
626  */
627 
628 void
629 hashcd(void)
630 {
631 	struct tblentry **pp;
632 	struct tblentry *cmdp;
633 
634 	for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
635 		for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
636 			if (cmdp->cmdtype == CMDNORMAL
637 			 || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0))
638 				cmdp->rehash = 1;
639 		}
640 	}
641 }
642 
643 
644 
645 /*
646  * Called before PATH is changed.  The argument is the new value of PATH;
647  * pathval() still returns the old value at this point.  Called with
648  * interrupts off.
649  */
650 
651 void
652 changepath(const char *newval)
653 {
654 	const char *old, *new;
655 	int idx;
656 	int firstchange;
657 	int bltin;
658 
659 	old = pathval();
660 	new = newval;
661 	firstchange = 9999;	/* assume no change */
662 	idx = 0;
663 	bltin = -1;
664 	for (;;) {
665 		if (*old != *new) {
666 			firstchange = idx;
667 			if ((*old == '\0' && *new == ':')
668 			 || (*old == ':' && *new == '\0'))
669 				firstchange++;
670 			old = new;	/* ignore subsequent differences */
671 		}
672 		if (*new == '\0')
673 			break;
674 		if (*new == '%' && bltin < 0 && prefix("builtin", new + 1))
675 			bltin = idx;
676 		if (*new == ':') {
677 			idx++;
678 		}
679 		new++, old++;
680 	}
681 	if (builtinloc < 0 && bltin >= 0)
682 		builtinloc = bltin;		/* zap builtins */
683 	if (builtinloc >= 0 && bltin < 0)
684 		firstchange = 0;
685 	clearcmdentry(firstchange);
686 	builtinloc = bltin;
687 }
688 
689 
690 /*
691  * Clear out command entries.  The argument specifies the first entry in
692  * PATH which has changed.
693  */
694 
695 STATIC void
696 clearcmdentry(int firstchange)
697 {
698 	struct tblentry **tblp;
699 	struct tblentry **pp;
700 	struct tblentry *cmdp;
701 
702 	INTOFF;
703 	for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
704 		pp = tblp;
705 		while ((cmdp = *pp) != NULL) {
706 			if ((cmdp->cmdtype == CMDNORMAL &&
707 			     cmdp->param.index >= firstchange)
708 			 || (cmdp->cmdtype == CMDBUILTIN &&
709 			     builtinloc >= firstchange)) {
710 				*pp = cmdp->next;
711 				ckfree(cmdp);
712 			} else {
713 				pp = &cmdp->next;
714 			}
715 		}
716 	}
717 	INTON;
718 }
719 
720 
721 /*
722  * Delete all functions.
723  */
724 
725 #ifdef mkinit
726 MKINIT void deletefuncs(void);
727 MKINIT void hash_special_builtins(void);
728 
729 INIT {
730 	hash_special_builtins();
731 }
732 
733 SHELLPROC {
734 	deletefuncs();
735 }
736 #endif
737 
738 void
739 deletefuncs(void)
740 {
741 	struct tblentry **tblp;
742 	struct tblentry **pp;
743 	struct tblentry *cmdp;
744 
745 	INTOFF;
746 	for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
747 		pp = tblp;
748 		while ((cmdp = *pp) != NULL) {
749 			if (cmdp->cmdtype == CMDFUNCTION) {
750 				*pp = cmdp->next;
751 				freefunc(cmdp->param.func);
752 				ckfree(cmdp);
753 			} else {
754 				pp = &cmdp->next;
755 			}
756 		}
757 	}
758 	INTON;
759 }
760 
761 
762 
763 /*
764  * Locate a command in the command hash table.  If "add" is nonzero,
765  * add the command to the table if it is not already present.  The
766  * variable "lastcmdentry" is set to point to the address of the link
767  * pointing to the entry, so that delete_cmd_entry can delete the
768  * entry.
769  */
770 
771 struct tblentry **lastcmdentry;
772 
773 
774 STATIC struct tblentry *
775 cmdlookup(const char *name, int add)
776 {
777 	int hashval;
778 	const char *p;
779 	struct tblentry *cmdp;
780 	struct tblentry **pp;
781 
782 	p = name;
783 	hashval = *p << 4;
784 	while (*p)
785 		hashval += *p++;
786 	hashval &= 0x7FFF;
787 	pp = &cmdtable[hashval % CMDTABLESIZE];
788 	for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
789 		if (equal(cmdp->cmdname, name))
790 			break;
791 		pp = &cmdp->next;
792 	}
793 	if (add && cmdp == NULL) {
794 		INTOFF;
795 		cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
796 					+ strlen(name) + 1);
797 		cmdp->next = NULL;
798 		cmdp->cmdtype = CMDUNKNOWN;
799 		cmdp->rehash = 0;
800 		strcpy(cmdp->cmdname, name);
801 		INTON;
802 	}
803 	lastcmdentry = pp;
804 	return cmdp;
805 }
806 
807 /*
808  * Delete the command entry returned on the last lookup.
809  */
810 
811 STATIC void
812 delete_cmd_entry(void)
813 {
814 	struct tblentry *cmdp;
815 
816 	INTOFF;
817 	cmdp = *lastcmdentry;
818 	*lastcmdentry = cmdp->next;
819 	ckfree(cmdp);
820 	INTON;
821 }
822 
823 
824 
825 #ifdef notdef
826 void
827 getcmdentry(char *name, struct cmdentry *entry)
828 {
829 	struct tblentry *cmdp = cmdlookup(name, 0);
830 
831 	if (cmdp) {
832 		entry->u = cmdp->param;
833 		entry->cmdtype = cmdp->cmdtype;
834 	} else {
835 		entry->cmdtype = CMDUNKNOWN;
836 		entry->u.index = 0;
837 	}
838 }
839 #endif
840 
841 
842 /*
843  * Add a new command entry, replacing any existing command entry for
844  * the same name - except special builtins.
845  */
846 
847 void
848 addcmdentry(char *name, struct cmdentry *entry)
849 {
850 	struct tblentry *cmdp;
851 
852 	INTOFF;
853 	cmdp = cmdlookup(name, 1);
854 	if (cmdp->cmdtype != CMDSPLBLTIN) {
855 		if (cmdp->cmdtype == CMDFUNCTION) {
856 			freefunc(cmdp->param.func);
857 		}
858 		cmdp->cmdtype = entry->cmdtype;
859 		cmdp->param = entry->u;
860 	}
861 	INTON;
862 }
863 
864 
865 /*
866  * Define a shell function.
867  */
868 
869 void
870 defun(char *name, union node *func)
871 {
872 	struct cmdentry entry;
873 
874 	INTOFF;
875 	entry.cmdtype = CMDFUNCTION;
876 	entry.u.func = copyfunc(func);
877 	addcmdentry(name, &entry);
878 	INTON;
879 }
880 
881 
882 /*
883  * Delete a function if it exists.
884  */
885 
886 int
887 unsetfunc(char *name)
888 {
889 	struct tblentry *cmdp;
890 
891 	if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->cmdtype == CMDFUNCTION) {
892 		freefunc(cmdp->param.func);
893 		delete_cmd_entry();
894 		return (0);
895 	}
896 	return (1);
897 }
898 
899 /*
900  * Locate and print what a word is...
901  */
902 
903 int
904 typecmd(int argc, char **argv)
905 {
906 	struct cmdentry entry;
907 	struct tblentry *cmdp;
908 	char * const *pp;
909 	struct alias *ap;
910 	int i;
911 	int err = 0;
912 
913 	for (i = 1; i < argc; i++) {
914 		out1str(argv[i]);
915 		/* First look at the keywords */
916 		for (pp = parsekwd; *pp; pp++)
917 			if (**pp == *argv[i] && equal(*pp, argv[i]))
918 				break;
919 
920 		if (*pp) {
921 			out1str(" is a shell keyword\n");
922 			continue;
923 		}
924 
925 		/* Then look at the aliases */
926 		if ((ap = lookupalias(argv[i], 1)) != NULL) {
927 			out1fmt(" is an alias for %s\n", ap->val);
928 			continue;
929 		}
930 
931 		/* Then check if it is a tracked alias */
932 		if ((cmdp = cmdlookup(argv[i], 0)) != NULL) {
933 			entry.cmdtype = cmdp->cmdtype;
934 			entry.u = cmdp->param;
935 		}
936 		else {
937 			/* Finally use brute force */
938 			find_command(argv[i], &entry, DO_ABS, pathval());
939 		}
940 
941 		switch (entry.cmdtype) {
942 		case CMDNORMAL: {
943 			if (strchr(argv[i], '/') == NULL) {
944 				const char *path = pathval();
945 				char *name;
946 				int j = entry.u.index;
947 				do {
948 					name = padvance(&path, argv[i]);
949 					stunalloc(name);
950 				} while (--j >= 0);
951 				out1fmt(" is%s %s\n",
952 				    cmdp ? " a tracked alias for" : "", name);
953 			} else {
954 				if (access(argv[i], X_OK) == 0)
955 					out1fmt(" is %s\n", argv[i]);
956 				else
957 					out1fmt(": %s\n", strerror(errno));
958 			}
959  			break;
960 		}
961 		case CMDFUNCTION:
962 			out1str(" is a shell function\n");
963 			break;
964 
965 		case CMDBUILTIN:
966 			out1str(" is a shell builtin\n");
967 			break;
968 
969 		case CMDSPLBLTIN:
970 			out1str(" is a special shell builtin\n");
971 			break;
972 
973 		default:
974 			out1str(": not found\n");
975 			err |= 127;
976 			break;
977 		}
978 	}
979 	return err;
980 }
981