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redir.c revision 1.36 
      1 /*	$NetBSD: redir.c,v 1.36 2014/10/15 14:54:25 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. 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 1.36 2014/10/15 14:54:25 christos 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 #define	CLOSED -1		/* fd was not open before redir */
     71 #ifndef PIPE_BUF
     72 # define PIPESIZE 4096		/* amount of buffering in a pipe */
     73 #else
     74 # define PIPESIZE PIPE_BUF
     75 #endif
     76 
     77 
     78 MKINIT
     79 struct redirtab {
     80 	struct redirtab *next;
     81 	short renamed[10];
     82 };
     83 
     84 
     85 MKINIT struct redirtab *redirlist;
     86 
     87 /*
     88  * We keep track of whether or not fd0 has been redirected.  This is for
     89  * background commands, where we want to redirect fd0 to /dev/null only
     90  * if it hasn't already been redirected.
     91 */
     92 int fd0_redirected = 0;
     93 
     94 STATIC void openredirect(union node *, char[10], int);
     95 STATIC int openhere(const union node *);
     96 
     97 
     98 /*
     99  * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
    100  * old file descriptors are stashed away so that the redirection can be
    101  * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
    102  * standard output, and the standard error if it becomes a duplicate of
    103  * stdout, is saved in memory.
    104  */
    105 
    106 void
    107 redirect(union node *redir, int flags)
    108 {
    109 	union node *n;
    110 	struct redirtab *sv = NULL;
    111 	int i;
    112 	int fd;
    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 		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
    131 		    n->ndup.dupfd == fd)
    132 			continue; /* redirect from/to same file descriptor */
    133 
    134 		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
    135 			INTOFF;
    136 			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
    137 				switch (errno) {
    138 				case EBADF:
    139 					i = CLOSED;
    140 					break;
    141 				default:
    142 					INTON;
    143 					error("%d: %s", fd, strerror(errno));
    144 					/* NOTREACHED */
    145 				}
    146 			} else
    147 				(void)fcntl(i, F_SETFD, FD_CLOEXEC);
    148 			sv->renamed[fd] = i;
    149 			INTON;
    150 		} else {
    151 			close(fd);
    152 		}
    153                 if (fd == 0)
    154                         fd0_redirected++;
    155 		openredirect(n, memory, flags);
    156 	}
    157 	if (memory[1])
    158 		out1 = &memout;
    159 	if (memory[2])
    160 		out2 = &memout;
    161 }
    162 
    163 
    164 STATIC void
    165 openredirect(union node *redir, char memory[10], int flags)
    166 {
    167 	struct stat sb;
    168 	int fd = redir->nfile.fd;
    169 	char *fname;
    170 	int f;
    171 	int eflags;
    172 
    173 	/*
    174 	 * We suppress interrupts so that we won't leave open file
    175 	 * descriptors around.  This may not be such a good idea because
    176 	 * an open of a device or a fifo can block indefinitely.
    177 	 */
    178 	INTOFF;
    179 	memory[fd] = 0;
    180 	switch (redir->nfile.type) {
    181 	case NFROM:
    182 		fname = redir->nfile.expfname;
    183 		if (flags & REDIR_VFORK)
    184 			eflags = O_NONBLOCK;
    185 		else
    186 			eflags = 0;
    187 		if ((f = open(fname, O_RDONLY|eflags)) < 0)
    188 			goto eopen;
    189 		if (eflags)
    190 			(void)fcntl(f, F_SETFL, fcntl(f, F_GETFL, 0) & ~eflags);
    191 		break;
    192 	case NFROMTO:
    193 		fname = redir->nfile.expfname;
    194 		if ((f = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
    195 			goto ecreate;
    196 		break;
    197 	case NTO:
    198 		if (Cflag) {
    199 			fname = redir->nfile.expfname;
    200 			if (stat(fname, &sb) == -1) {
    201 				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL,
    202 				    0666)) < 0)
    203 					goto ecreate;
    204 			} else if (!S_ISREG(sb.st_mode)) {
    205 				if ((f = open(fname, O_WRONLY, 0666)) < 0)
    206 					goto ecreate;
    207 				if (fstat(f, &sb) != -1 &&
    208 				    S_ISREG(sb.st_mode)) {
    209 					close(f);
    210 					errno = EEXIST;
    211 					goto ecreate;
    212 				}
    213 			} else {
    214 				errno = EEXIST;
    215 				goto ecreate;
    216 			}
    217 			break;
    218 		}
    219 		/* FALLTHROUGH */
    220 	case NCLOBBER:
    221 		fname = redir->nfile.expfname;
    222 		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
    223 			goto ecreate;
    224 		break;
    225 	case NAPPEND:
    226 		fname = redir->nfile.expfname;
    227 		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
    228 			goto ecreate;
    229 		break;
    230 	case NTOFD:
    231 	case NFROMFD:
    232 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
    233 			if (memory[redir->ndup.dupfd])
    234 				memory[fd] = 1;
    235 			else
    236 				copyfd(redir->ndup.dupfd, fd, 1);
    237 		}
    238 		INTON;
    239 		return;
    240 	case NHERE:
    241 	case NXHERE:
    242 		f = openhere(redir);
    243 		break;
    244 	default:
    245 		abort();
    246 	}
    247 
    248 	if (f != fd) {
    249 		copyfd(f, fd, 1);
    250 		close(f);
    251 	}
    252 	INTON;
    253 	return;
    254 ecreate:
    255 	exerrno = 1;
    256 	error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
    257 eopen:
    258 	exerrno = 1;
    259 	error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
    260 }
    261 
    262 
    263 /*
    264  * Handle here documents.  Normally we fork off a process to write the
    265  * data to a pipe.  If the document is short, we can stuff the data in
    266  * the pipe without forking.
    267  */
    268 
    269 STATIC int
    270 openhere(const union node *redir)
    271 {
    272 	int pip[2];
    273 	int len = 0;
    274 
    275 	if (pipe(pip) < 0)
    276 		error("Pipe call failed");
    277 	if (redir->type == NHERE) {
    278 		len = strlen(redir->nhere.doc->narg.text);
    279 		if (len <= PIPESIZE) {
    280 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    281 			goto out;
    282 		}
    283 	}
    284 	if (forkshell(NULL, NULL, FORK_NOJOB) == 0) {
    285 		close(pip[0]);
    286 		signal(SIGINT, SIG_IGN);
    287 		signal(SIGQUIT, SIG_IGN);
    288 		signal(SIGHUP, SIG_IGN);
    289 #ifdef SIGTSTP
    290 		signal(SIGTSTP, SIG_IGN);
    291 #endif
    292 		signal(SIGPIPE, SIG_DFL);
    293 		if (redir->type == NHERE)
    294 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    295 		else
    296 			expandhere(redir->nhere.doc, pip[1]);
    297 		_exit(0);
    298 	}
    299 out:
    300 	close(pip[1]);
    301 	return pip[0];
    302 }
    303 
    304 
    305 
    306 /*
    307  * Undo the effects of the last redirection.
    308  */
    309 
    310 void
    311 popredir(void)
    312 {
    313 	struct redirtab *rp = redirlist;
    314 	int i;
    315 
    316 	for (i = 0 ; i < 10 ; i++) {
    317 		if (rp->renamed[i] != EMPTY) {
    318                         if (i == 0)
    319                                 fd0_redirected--;
    320 			close(i);
    321 			if (rp->renamed[i] >= 0) {
    322 				copyfd(rp->renamed[i], i, 1);
    323 				close(rp->renamed[i]);
    324 			}
    325 		}
    326 	}
    327 	INTOFF;
    328 	redirlist = rp->next;
    329 	ckfree(rp);
    330 	INTON;
    331 }
    332 
    333 /*
    334  * Undo all redirections.  Called on error or interrupt.
    335  */
    336 
    337 #ifdef mkinit
    338 
    339 INCLUDE "redir.h"
    340 
    341 RESET {
    342 	while (redirlist)
    343 		popredir();
    344 }
    345 
    346 SHELLPROC {
    347 	clearredir(0);
    348 }
    349 
    350 #endif
    351 
    352 /* Return true if fd 0 has already been redirected at least once.  */
    353 int
    354 fd0_redirected_p (void) {
    355         return fd0_redirected != 0;
    356 }
    357 
    358 /*
    359  * Discard all saved file descriptors.
    360  */
    361 
    362 void
    363 clearredir(int vforked)
    364 {
    365 	struct redirtab *rp;
    366 	int i;
    367 
    368 	for (rp = redirlist ; rp ; rp = rp->next) {
    369 		for (i = 0 ; i < 10 ; i++) {
    370 			if (rp->renamed[i] >= 0) {
    371 				close(rp->renamed[i]);
    372 			}
    373 			if (!vforked)
    374 				rp->renamed[i] = EMPTY;
    375 		}
    376 	}
    377 }
    378 
    379 
    380 
    381 /*
    382  * Copy a file descriptor to be >= to.  Returns -1
    383  * if the source file descriptor is closed, EMPTY if there are no unused
    384  * file descriptors left.
    385  */
    386 
    387 int
    388 copyfd(int from, int to, int equal)
    389 {
    390 	int newfd;
    391 
    392 	if (equal)
    393 		newfd = dup2(from, to);
    394 	else
    395 		newfd = fcntl(from, F_DUPFD, to);
    396 	if (newfd < 0) {
    397 		if (errno == EMFILE)
    398 			return EMPTY;
    399 		else
    400 			error("%d: %s", from, strerror(errno));
    401 	}
    402 	return newfd;
    403 }
    404