redir.c revision 246288 
1/*-
2 * Copyright (c) 1991, 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 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#ifndef lint
34#if 0
35static char sccsid[] = "@(#)redir.c	8.2 (Berkeley) 5/4/95";
36#endif
37#endif /* not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: head/bin/sh/redir.c 246288 2013-02-03 15:54:57Z jilles $");
40
41#include <sys/types.h>
42#include <sys/stat.h>
43#include <signal.h>
44#include <string.h>
45#include <fcntl.h>
46#include <errno.h>
47#include <unistd.h>
48#include <stdlib.h>
49
50/*
51 * Code for dealing with input/output redirection.
52 */
53
54#include "shell.h"
55#include "nodes.h"
56#include "jobs.h"
57#include "expand.h"
58#include "redir.h"
59#include "output.h"
60#include "memalloc.h"
61#include "error.h"
62#include "options.h"
63
64
65#define EMPTY -2		/* marks an unused slot in redirtab */
66#define CLOSED -1		/* fd was not open before redir */
67#define PIPESIZE 4096		/* amount of buffering in a pipe */
68
69
70MKINIT
71struct redirtab {
72	struct redirtab *next;
73	int renamed[10];
74};
75
76
77MKINIT struct redirtab *redirlist;
78
79/*
80 * We keep track of whether or not fd0 has been redirected.  This is for
81 * background commands, where we want to redirect fd0 to /dev/null only
82 * if it hasn't already been redirected.
83*/
84static int fd0_redirected = 0;
85
86static void openredirect(union node *, char[10 ]);
87static int openhere(union node *);
88
89
90/*
91 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
92 * old file descriptors are stashed away so that the redirection can be
93 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
94 * standard output, and the standard error if it becomes a duplicate of
95 * stdout, is saved in memory.
96 */
97
98void
99redirect(union node *redir, int flags)
100{
101	union node *n;
102	struct redirtab *sv = NULL;
103	int i;
104	int fd;
105	char memory[10];	/* file descriptors to write to memory */
106
107	for (i = 10 ; --i >= 0 ; )
108		memory[i] = 0;
109	memory[1] = flags & REDIR_BACKQ;
110	if (flags & REDIR_PUSH) {
111		sv = ckmalloc(sizeof (struct redirtab));
112		for (i = 0 ; i < 10 ; i++)
113			sv->renamed[i] = EMPTY;
114		sv->next = redirlist;
115		redirlist = sv;
116	}
117	for (n = redir ; n ; n = n->nfile.next) {
118		fd = n->nfile.fd;
119		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
120		    n->ndup.dupfd == fd)
121			continue; /* redirect from/to same file descriptor */
122
123		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
124			INTOFF;
125			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
126				switch (errno) {
127				case EBADF:
128					i = CLOSED;
129					break;
130				default:
131					INTON;
132					error("%d: %s", fd, strerror(errno));
133					break;
134				}
135			} else
136				(void)fcntl(i, F_SETFD, FD_CLOEXEC);
137			sv->renamed[fd] = i;
138			INTON;
139		}
140		if (fd == 0)
141			fd0_redirected++;
142		openredirect(n, memory);
143	}
144	if (memory[1])
145		out1 = &memout;
146	if (memory[2])
147		out2 = &memout;
148}
149
150
151static void
152openredirect(union node *redir, char memory[10])
153{
154	struct stat sb;
155	int fd = redir->nfile.fd;
156	char *fname;
157	int f;
158	int e;
159
160	/*
161	 * We suppress interrupts so that we won't leave open file
162	 * descriptors around.  Because the signal handler remains
163	 * installed and we do not use system call restart, interrupts
164	 * will still abort blocking opens such as fifos (they will fail
165	 * with EINTR). There is, however, a race condition if an interrupt
166	 * arrives after INTOFF and before open blocks.
167	 */
168	INTOFF;
169	memory[fd] = 0;
170	switch (redir->nfile.type) {
171	case NFROM:
172		fname = redir->nfile.expfname;
173		if ((f = open(fname, O_RDONLY)) < 0)
174			error("cannot open %s: %s", fname, strerror(errno));
175movefd:
176		if (f != fd) {
177			if (dup2(f, fd) == -1) {
178				e = errno;
179				close(f);
180				error("%d: %s", fd, strerror(e));
181			}
182			close(f);
183		}
184		break;
185	case NFROMTO:
186		fname = redir->nfile.expfname;
187		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
188			error("cannot create %s: %s", fname, strerror(errno));
189		goto movefd;
190	case NTO:
191		if (Cflag) {
192			fname = redir->nfile.expfname;
193			if (stat(fname, &sb) == -1) {
194				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
195					error("cannot create %s: %s", fname, strerror(errno));
196			} else if (!S_ISREG(sb.st_mode)) {
197				if ((f = open(fname, O_WRONLY, 0666)) < 0)
198					error("cannot create %s: %s", fname, strerror(errno));
199				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
200					close(f);
201					error("cannot create %s: %s", fname,
202					    strerror(EEXIST));
203				}
204			} else
205				error("cannot create %s: %s", fname,
206				    strerror(EEXIST));
207			goto movefd;
208		}
209		/* FALLTHROUGH */
210	case NCLOBBER:
211		fname = redir->nfile.expfname;
212		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
213			error("cannot create %s: %s", fname, strerror(errno));
214		goto movefd;
215	case NAPPEND:
216		fname = redir->nfile.expfname;
217		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
218			error("cannot create %s: %s", fname, strerror(errno));
219		goto movefd;
220	case NTOFD:
221	case NFROMFD:
222		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
223			if (memory[redir->ndup.dupfd])
224				memory[fd] = 1;
225			else {
226				if (dup2(redir->ndup.dupfd, fd) < 0)
227					error("%d: %s", redir->ndup.dupfd,
228							strerror(errno));
229			}
230		} else {
231			close(fd);
232		}
233		break;
234	case NHERE:
235	case NXHERE:
236		f = openhere(redir);
237		goto movefd;
238	default:
239		abort();
240	}
241	INTON;
242}
243
244
245/*
246 * Handle here documents.  Normally we fork off a process to write the
247 * data to a pipe.  If the document is short, we can stuff the data in
248 * the pipe without forking.
249 */
250
251static int
252openhere(union node *redir)
253{
254	char *p;
255	int pip[2];
256	int len = 0;
257
258	if (pipe(pip) < 0)
259		error("Pipe call failed: %s", strerror(errno));
260
261	if (redir->type == NXHERE)
262		p = redir->nhere.expdoc;
263	else
264		p = redir->nhere.doc->narg.text;
265	len = strlen(p);
266	if (len <= PIPESIZE) {
267		xwrite(pip[1], p, len);
268		goto out;
269	}
270
271	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
272		close(pip[0]);
273		signal(SIGINT, SIG_IGN);
274		signal(SIGQUIT, SIG_IGN);
275		signal(SIGHUP, SIG_IGN);
276		signal(SIGTSTP, SIG_IGN);
277		signal(SIGPIPE, SIG_DFL);
278		xwrite(pip[1], p, len);
279		_exit(0);
280	}
281out:
282	close(pip[1]);
283	return pip[0];
284}
285
286
287
288/*
289 * Undo the effects of the last redirection.
290 */
291
292void
293popredir(void)
294{
295	struct redirtab *rp = redirlist;
296	int i;
297
298	for (i = 0 ; i < 10 ; i++) {
299		if (rp->renamed[i] != EMPTY) {
300                        if (i == 0)
301                                fd0_redirected--;
302			if (rp->renamed[i] >= 0) {
303				dup2(rp->renamed[i], i);
304				close(rp->renamed[i]);
305			} else {
306				close(i);
307			}
308		}
309	}
310	INTOFF;
311	redirlist = rp->next;
312	ckfree(rp);
313	INTON;
314}
315
316/*
317 * Undo all redirections.  Called on error or interrupt.
318 */
319
320#ifdef mkinit
321
322INCLUDE "redir.h"
323
324RESET {
325	while (redirlist)
326		popredir();
327}
328
329#endif
330
331/* Return true if fd 0 has already been redirected at least once.  */
332int
333fd0_redirected_p(void)
334{
335        return fd0_redirected != 0;
336}
337
338/*
339 * Discard all saved file descriptors.
340 */
341
342void
343clearredir(void)
344{
345	struct redirtab *rp;
346	int i;
347
348	for (rp = redirlist ; rp ; rp = rp->next) {
349		for (i = 0 ; i < 10 ; i++) {
350			if (rp->renamed[i] >= 0) {
351				close(rp->renamed[i]);
352			}
353			rp->renamed[i] = EMPTY;
354		}
355	}
356}
357