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redir.c revision 1.27 
      1 /*	$NetBSD: redir.c,v 1.27 2002/11/24 22:35:42 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[] = "@(#)redir.c	8.2 (Berkeley) 5/4/95";
     43 #else
     44 __RCSID("$NetBSD: redir.c,v 1.27 2002/11/24 22:35:42 christos Exp $");
     45 #endif
     46 #endif /* not lint */
     47 
     48 #include <sys/types.h>
     49 #include <sys/param.h>	/* PIPE_BUF */
     50 #include <signal.h>
     51 #include <string.h>
     52 #include <fcntl.h>
     53 #include <errno.h>
     54 #include <unistd.h>
     55 #include <stdlib.h>
     56 
     57 /*
     58  * Code for dealing with input/output redirection.
     59  */
     60 
     61 #include "main.h"
     62 #include "shell.h"
     63 #include "nodes.h"
     64 #include "jobs.h"
     65 #include "options.h"
     66 #include "expand.h"
     67 #include "redir.h"
     68 #include "output.h"
     69 #include "memalloc.h"
     70 #include "error.h"
     71 
     72 
     73 #define EMPTY -2		/* marks an unused slot in redirtab */
     74 #ifndef PIPE_BUF
     75 # define PIPESIZE 4096		/* amount of buffering in a pipe */
     76 #else
     77 # define PIPESIZE PIPE_BUF
     78 #endif
     79 
     80 
     81 MKINIT
     82 struct redirtab {
     83 	struct redirtab *next;
     84 	short renamed[10];
     85 };
     86 
     87 
     88 MKINIT struct redirtab *redirlist;
     89 
     90 /*
     91  * We keep track of whether or not fd0 has been redirected.  This is for
     92  * background commands, where we want to redirect fd0 to /dev/null only
     93  * if it hasn't already been redirected.
     94 */
     95 int fd0_redirected = 0;
     96 
     97 STATIC void openredirect(union node *, char[10 ]);
     98 STATIC int openhere(union node *);
     99 
    100 
    101 /*
    102  * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
    103  * old file descriptors are stashed away so that the redirection can be
    104  * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
    105  * standard output, and the standard error if it becomes a duplicate of
    106  * stdout, is saved in memory.
    107  */
    108 
    109 void
    110 redirect(union node *redir, int flags)
    111 {
    112 	union node *n;
    113 	struct redirtab *sv = NULL;
    114 	int i;
    115 	int fd;
    116 	int try;
    117 	char memory[10];	/* file descriptors to write to memory */
    118 
    119 	for (i = 10 ; --i >= 0 ; )
    120 		memory[i] = 0;
    121 	memory[1] = flags & REDIR_BACKQ;
    122 	if (flags & REDIR_PUSH) {
    123 		/* We don't have to worry about REDIR_VFORK here, as
    124 		 * flags & REDIR_PUSH is never true if REDIR_VFORK is set.
    125 		 */
    126 		sv = ckmalloc(sizeof (struct redirtab));
    127 		for (i = 0 ; i < 10 ; i++)
    128 			sv->renamed[i] = EMPTY;
    129 		sv->next = redirlist;
    130 		redirlist = sv;
    131 	}
    132 	for (n = redir ; n ; n = n->nfile.next) {
    133 		fd = n->nfile.fd;
    134 		try = 0;
    135 		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
    136 		    n->ndup.dupfd == fd)
    137 			continue; /* redirect from/to same file descriptor */
    138 
    139 		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
    140 			INTOFF;
    141 again:
    142 			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
    143 				switch (errno) {
    144 				case EBADF:
    145 					if (!try) {
    146 						openredirect(n, memory);
    147 						try++;
    148 						goto again;
    149 					}
    150 					/* FALLTHROUGH*/
    151 				default:
    152 					INTON;
    153 					error("%d: %s", fd, strerror(errno));
    154 					/* NOTREACHED */
    155 				}
    156 			}
    157 			if (!try) {
    158 				sv->renamed[fd] = i;
    159 				close(fd);
    160 			}
    161 			INTON;
    162 		} else {
    163 			close(fd);
    164 		}
    165                 if (fd == 0)
    166                         fd0_redirected++;
    167 		if (!try)
    168 			openredirect(n, memory);
    169 	}
    170 	if (memory[1])
    171 		out1 = &memout;
    172 	if (memory[2])
    173 		out2 = &memout;
    174 }
    175 
    176 
    177 STATIC void
    178 openredirect(union node *redir, char memory[10])
    179 {
    180 	int fd = redir->nfile.fd;
    181 	char *fname;
    182 	int f;
    183 	int flags = O_WRONLY|O_CREAT|O_TRUNC;
    184 
    185 	/*
    186 	 * We suppress interrupts so that we won't leave open file
    187 	 * descriptors around.  This may not be such a good idea because
    188 	 * an open of a device or a fifo can block indefinitely.
    189 	 */
    190 	INTOFF;
    191 	memory[fd] = 0;
    192 	switch (redir->nfile.type) {
    193 	case NFROM:
    194 		fname = redir->nfile.expfname;
    195 		if ((f = open(fname, O_RDONLY)) < 0)
    196 			goto eopen;
    197 		break;
    198 	case NFROMTO:
    199 		fname = redir->nfile.expfname;
    200 		if ((f = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
    201 			goto ecreate;
    202 		break;
    203 	case NTO:
    204 		if (Cflag)
    205 			flags |= O_EXCL;
    206 		/* FALLTHROUGH */
    207 	case NCLOBBER:
    208 		fname = redir->nfile.expfname;
    209 		if ((f = open(fname, flags, 0666)) < 0)
    210 			goto ecreate;
    211 		break;
    212 	case NAPPEND:
    213 		fname = redir->nfile.expfname;
    214 		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
    215 			goto ecreate;
    216 		break;
    217 	case NTOFD:
    218 	case NFROMFD:
    219 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
    220 			if (memory[redir->ndup.dupfd])
    221 				memory[fd] = 1;
    222 			else
    223 				copyfd(redir->ndup.dupfd, fd);
    224 		}
    225 		INTON;
    226 		return;
    227 	case NHERE:
    228 	case NXHERE:
    229 		f = openhere(redir);
    230 		break;
    231 	default:
    232 		abort();
    233 	}
    234 
    235 	if (f != fd) {
    236 		copyfd(f, fd);
    237 		close(f);
    238 	}
    239 	INTON;
    240 	return;
    241 ecreate:
    242 	error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
    243 eopen:
    244 	error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
    245 }
    246 
    247 
    248 /*
    249  * Handle here documents.  Normally we fork off a process to write the
    250  * data to a pipe.  If the document is short, we can stuff the data in
    251  * the pipe without forking.
    252  */
    253 
    254 STATIC int
    255 openhere(union node *redir)
    256 {
    257 	int pip[2];
    258 	int len = 0;
    259 
    260 	if (pipe(pip) < 0)
    261 		error("Pipe call failed");
    262 	if (redir->type == NHERE) {
    263 		len = strlen(redir->nhere.doc->narg.text);
    264 		if (len <= PIPESIZE) {
    265 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    266 			goto out;
    267 		}
    268 	}
    269 	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
    270 		close(pip[0]);
    271 		signal(SIGINT, SIG_IGN);
    272 		signal(SIGQUIT, SIG_IGN);
    273 		signal(SIGHUP, SIG_IGN);
    274 #ifdef SIGTSTP
    275 		signal(SIGTSTP, SIG_IGN);
    276 #endif
    277 		signal(SIGPIPE, SIG_DFL);
    278 		if (redir->type == NHERE)
    279 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    280 		else
    281 			expandhere(redir->nhere.doc, pip[1]);
    282 		_exit(0);
    283 	}
    284 out:
    285 	close(pip[1]);
    286 	return pip[0];
    287 }
    288 
    289 
    290 
    291 /*
    292  * Undo the effects of the last redirection.
    293  */
    294 
    295 void
    296 popredir(void)
    297 {
    298 	struct redirtab *rp = redirlist;
    299 	int i;
    300 
    301 	for (i = 0 ; i < 10 ; i++) {
    302 		if (rp->renamed[i] != EMPTY) {
    303                         if (i == 0)
    304                                 fd0_redirected--;
    305 			close(i);
    306 			if (rp->renamed[i] >= 0) {
    307 				copyfd(rp->renamed[i], i);
    308 				close(rp->renamed[i]);
    309 			}
    310 		}
    311 	}
    312 	INTOFF;
    313 	redirlist = rp->next;
    314 	ckfree(rp);
    315 	INTON;
    316 }
    317 
    318 /*
    319  * Undo all redirections.  Called on error or interrupt.
    320  */
    321 
    322 #ifdef mkinit
    323 
    324 INCLUDE "redir.h"
    325 
    326 RESET {
    327 	while (redirlist)
    328 		popredir();
    329 }
    330 
    331 SHELLPROC {
    332 	clearredir(0);
    333 }
    334 
    335 #endif
    336 
    337 /* Return true if fd 0 has already been redirected at least once.  */
    338 int
    339 fd0_redirected_p () {
    340         return fd0_redirected != 0;
    341 }
    342 
    343 /*
    344  * Discard all saved file descriptors.
    345  */
    346 
    347 void
    348 clearredir(vforked)
    349 	int vforked;
    350 {
    351 	struct redirtab *rp;
    352 	int i;
    353 
    354 	for (rp = redirlist ; rp ; rp = rp->next) {
    355 		for (i = 0 ; i < 10 ; i++) {
    356 			if (rp->renamed[i] >= 0) {
    357 				close(rp->renamed[i]);
    358 			}
    359 			if (!vforked)
    360 				rp->renamed[i] = EMPTY;
    361 		}
    362 	}
    363 }
    364 
    365 
    366 
    367 /*
    368  * Copy a file descriptor to be >= to.  Returns -1
    369  * if the source file descriptor is closed, EMPTY if there are no unused
    370  * file descriptors left.
    371  */
    372 
    373 int
    374 copyfd(int from, int to)
    375 {
    376 	int newfd;
    377 
    378 	newfd = fcntl(from, F_DUPFD, to);
    379 	if (newfd < 0) {
    380 		if (errno == EMFILE)
    381 			return EMPTY;
    382 		else
    383 			error("%d: %s", from, strerror(errno));
    384 	}
    385 	return newfd;
    386 }
    387