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redir.c revision 1.33 
      1 /*	$NetBSD: redir.c,v 1.33 2012/03/20 18:42:29 matt 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. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 #if 0
     38 static char sccsid[] = "@(#)redir.c	8.2 (Berkeley) 5/4/95";
     39 #else
     40 __RCSID("$NetBSD: redir.c,v 1.33 2012/03/20 18:42:29 matt Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <sys/types.h>
     45 #include <sys/param.h>	/* PIPE_BUF */
     46 #include <signal.h>
     47 #include <string.h>
     48 #include <fcntl.h>
     49 #include <errno.h>
     50 #include <unistd.h>
     51 #include <stdlib.h>
     52 
     53 /*
     54  * Code for dealing with input/output redirection.
     55  */
     56 
     57 #include "main.h"
     58 #include "shell.h"
     59 #include "nodes.h"
     60 #include "jobs.h"
     61 #include "options.h"
     62 #include "expand.h"
     63 #include "redir.h"
     64 #include "output.h"
     65 #include "memalloc.h"
     66 #include "error.h"
     67 
     68 
     69 #define EMPTY -2		/* marks an unused slot in redirtab */
     70 #ifndef PIPE_BUF
     71 # define PIPESIZE 4096		/* amount of buffering in a pipe */
     72 #else
     73 # define PIPESIZE PIPE_BUF
     74 #endif
     75 
     76 
     77 MKINIT
     78 struct redirtab {
     79 	struct redirtab *next;
     80 	short renamed[10];
     81 };
     82 
     83 
     84 MKINIT struct redirtab *redirlist;
     85 
     86 /*
     87  * We keep track of whether or not fd0 has been redirected.  This is for
     88  * background commands, where we want to redirect fd0 to /dev/null only
     89  * if it hasn't already been redirected.
     90 */
     91 int fd0_redirected = 0;
     92 
     93 STATIC void openredirect(union node *, char[10], int);
     94 STATIC int openhere(union node *);
     95 
     96 
     97 /*
     98  * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
     99  * old file descriptors are stashed away so that the redirection can be
    100  * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
    101  * standard output, and the standard error if it becomes a duplicate of
    102  * stdout, is saved in memory.
    103  */
    104 
    105 void
    106 redirect(union node *redir, int flags)
    107 {
    108 	union node *n;
    109 	struct redirtab *sv = NULL;
    110 	int i;
    111 	int fd;
    112 	int try;
    113 	char memory[10];	/* file descriptors to write to memory */
    114 
    115 	for (i = 10 ; --i >= 0 ; )
    116 		memory[i] = 0;
    117 	memory[1] = flags & REDIR_BACKQ;
    118 	if (flags & REDIR_PUSH) {
    119 		/* We don't have to worry about REDIR_VFORK here, as
    120 		 * flags & REDIR_PUSH is never true if REDIR_VFORK is set.
    121 		 */
    122 		sv = ckmalloc(sizeof (struct redirtab));
    123 		for (i = 0 ; i < 10 ; i++)
    124 			sv->renamed[i] = EMPTY;
    125 		sv->next = redirlist;
    126 		redirlist = sv;
    127 	}
    128 	for (n = redir ; n ; n = n->nfile.next) {
    129 		fd = n->nfile.fd;
    130 		try = 0;
    131 		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
    132 		    n->ndup.dupfd == fd)
    133 			continue; /* redirect from/to same file descriptor */
    134 
    135 		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
    136 			INTOFF;
    137 again:
    138 			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
    139 				switch (errno) {
    140 				case EBADF:
    141 					if (!try) {
    142 						openredirect(n, memory, flags);
    143 						try++;
    144 						goto again;
    145 					}
    146 					/* FALLTHROUGH*/
    147 				default:
    148 					INTON;
    149 					error("%d: %s", fd, strerror(errno));
    150 					/* NOTREACHED */
    151 				}
    152 			}
    153 			if (!try) {
    154 				sv->renamed[fd] = i;
    155 				close(fd);
    156 			}
    157 			INTON;
    158 		} else {
    159 			close(fd);
    160 		}
    161                 if (fd == 0)
    162                         fd0_redirected++;
    163 		if (!try)
    164 			openredirect(n, memory, flags);
    165 	}
    166 	if (memory[1])
    167 		out1 = &memout;
    168 	if (memory[2])
    169 		out2 = &memout;
    170 }
    171 
    172 
    173 STATIC void
    174 openredirect(union node *redir, char memory[10], int flags)
    175 {
    176 	int fd = redir->nfile.fd;
    177 	char *fname;
    178 	int f;
    179 	int oflags = O_WRONLY|O_CREAT|O_TRUNC, eflags;
    180 
    181 	/*
    182 	 * We suppress interrupts so that we won't leave open file
    183 	 * descriptors around.  This may not be such a good idea because
    184 	 * an open of a device or a fifo can block indefinitely.
    185 	 */
    186 	INTOFF;
    187 	memory[fd] = 0;
    188 	switch (redir->nfile.type) {
    189 	case NFROM:
    190 		fname = redir->nfile.expfname;
    191 		if (flags & REDIR_VFORK)
    192 			eflags = O_NONBLOCK;
    193 		else
    194 			eflags = 0;
    195 		if ((f = open(fname, O_RDONLY|eflags)) < 0)
    196 			goto eopen;
    197 		if (eflags)
    198 			(void)fcntl(f, F_SETFL, fcntl(f, F_GETFL, 0) & ~eflags);
    199 		break;
    200 	case NFROMTO:
    201 		fname = redir->nfile.expfname;
    202 		if ((f = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
    203 			goto ecreate;
    204 		break;
    205 	case NTO:
    206 		if (Cflag)
    207 			oflags |= O_EXCL;
    208 		/* FALLTHROUGH */
    209 	case NCLOBBER:
    210 		fname = redir->nfile.expfname;
    211 		if ((f = open(fname, oflags, 0666)) < 0)
    212 			goto ecreate;
    213 		break;
    214 	case NAPPEND:
    215 		fname = redir->nfile.expfname;
    216 		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
    217 			goto ecreate;
    218 		break;
    219 	case NTOFD:
    220 	case NFROMFD:
    221 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
    222 			if (memory[redir->ndup.dupfd])
    223 				memory[fd] = 1;
    224 			else
    225 				copyfd(redir->ndup.dupfd, fd, 1);
    226 		}
    227 		INTON;
    228 		return;
    229 	case NHERE:
    230 	case NXHERE:
    231 		f = openhere(redir);
    232 		break;
    233 	default:
    234 		abort();
    235 	}
    236 
    237 	if (f != fd) {
    238 		copyfd(f, fd, 1);
    239 		close(f);
    240 	}
    241 	INTON;
    242 	return;
    243 ecreate:
    244 	exerrno = 1;
    245 	error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
    246 eopen:
    247 	exerrno = 1;
    248 	error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
    249 }
    250 
    251 
    252 /*
    253  * Handle here documents.  Normally we fork off a process to write the
    254  * data to a pipe.  If the document is short, we can stuff the data in
    255  * the pipe without forking.
    256  */
    257 
    258 STATIC int
    259 openhere(union node *redir)
    260 {
    261 	int pip[2];
    262 	int len = 0;
    263 
    264 	if (pipe(pip) < 0)
    265 		error("Pipe call failed");
    266 	if (redir->type == NHERE) {
    267 		len = strlen(redir->nhere.doc->narg.text);
    268 		if (len <= PIPESIZE) {
    269 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    270 			goto out;
    271 		}
    272 	}
    273 	if (forkshell(NULL, NULL, FORK_NOJOB) == 0) {
    274 		close(pip[0]);
    275 		signal(SIGINT, SIG_IGN);
    276 		signal(SIGQUIT, SIG_IGN);
    277 		signal(SIGHUP, SIG_IGN);
    278 #ifdef SIGTSTP
    279 		signal(SIGTSTP, SIG_IGN);
    280 #endif
    281 		signal(SIGPIPE, SIG_DFL);
    282 		if (redir->type == NHERE)
    283 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    284 		else
    285 			expandhere(redir->nhere.doc, pip[1]);
    286 		_exit(0);
    287 	}
    288 out:
    289 	close(pip[1]);
    290 	return pip[0];
    291 }
    292 
    293 
    294 
    295 /*
    296  * Undo the effects of the last redirection.
    297  */
    298 
    299 void
    300 popredir(void)
    301 {
    302 	struct redirtab *rp = redirlist;
    303 	int i;
    304 
    305 	for (i = 0 ; i < 10 ; i++) {
    306 		if (rp->renamed[i] != EMPTY) {
    307                         if (i == 0)
    308                                 fd0_redirected--;
    309 			close(i);
    310 			if (rp->renamed[i] >= 0) {
    311 				copyfd(rp->renamed[i], i, 1);
    312 				close(rp->renamed[i]);
    313 			}
    314 		}
    315 	}
    316 	INTOFF;
    317 	redirlist = rp->next;
    318 	ckfree(rp);
    319 	INTON;
    320 }
    321 
    322 /*
    323  * Undo all redirections.  Called on error or interrupt.
    324  */
    325 
    326 #ifdef mkinit
    327 
    328 INCLUDE "redir.h"
    329 
    330 RESET {
    331 	while (redirlist)
    332 		popredir();
    333 }
    334 
    335 SHELLPROC {
    336 	clearredir(0);
    337 }
    338 
    339 #endif
    340 
    341 /* Return true if fd 0 has already been redirected at least once.  */
    342 int
    343 fd0_redirected_p (void) {
    344         return fd0_redirected != 0;
    345 }
    346 
    347 /*
    348  * Discard all saved file descriptors.
    349  */
    350 
    351 void
    352 clearredir(int vforked)
    353 {
    354 	struct redirtab *rp;
    355 	int i;
    356 
    357 	for (rp = redirlist ; rp ; rp = rp->next) {
    358 		for (i = 0 ; i < 10 ; i++) {
    359 			if (rp->renamed[i] >= 0) {
    360 				close(rp->renamed[i]);
    361 			}
    362 			if (!vforked)
    363 				rp->renamed[i] = EMPTY;
    364 		}
    365 	}
    366 }
    367 
    368 
    369 
    370 /*
    371  * Copy a file descriptor to be >= to.  Returns -1
    372  * if the source file descriptor is closed, EMPTY if there are no unused
    373  * file descriptors left.
    374  */
    375 
    376 int
    377 copyfd(int from, int to, int equal)
    378 {
    379 	int newfd;
    380 
    381 	if (equal)
    382 		newfd = dup2(from, to);
    383 	else
    384 		newfd = fcntl(from, F_DUPFD, to);
    385 	if (newfd < 0) {
    386 		if (errno == EMFILE)
    387 			return EMPTY;
    388 		else
    389 			error("%d: %s", from, strerror(errno));
    390 	}
    391 	return newfd;
    392 }
    393