redir.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 * 4. 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#ifndef lint
36#if 0
37static char sccsid[] = "@(#)redir.c	8.2 (Berkeley) 5/4/95";
38#endif
39#endif /* not lint */
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: stable/11/bin/sh/redir.c 330897 2018-03-14 03:19:51Z eadler $");
42
43#include <sys/types.h>
44#include <sys/stat.h>
45#include <signal.h>
46#include <string.h>
47#include <fcntl.h>
48#include <errno.h>
49#include <unistd.h>
50#include <stdlib.h>
51
52/*
53 * Code for dealing with input/output redirection.
54 */
55
56#include "shell.h"
57#include "nodes.h"
58#include "jobs.h"
59#include "expand.h"
60#include "redir.h"
61#include "output.h"
62#include "memalloc.h"
63#include "error.h"
64#include "options.h"
65
66
67#define EMPTY -2		/* marks an unused slot in redirtab */
68#define CLOSED -1		/* fd was not open before redir */
69
70
71struct redirtab {
72	struct redirtab *next;
73	int renamed[10];
74	int fd0_redirected;
75	unsigned int empty_redirs;
76};
77
78
79static struct redirtab *redirlist;
80
81/*
82 * We keep track of whether or not fd0 has been redirected.  This is for
83 * background commands, where we want to redirect fd0 to /dev/null only
84 * if it hasn't already been redirected.
85*/
86static int fd0_redirected = 0;
87
88/* Number of redirtabs that have not been allocated. */
89static unsigned int empty_redirs = 0;
90
91static void openredirect(union node *, char[10 ]);
92static int openhere(union node *);
93
94
95/*
96 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
97 * old file descriptors are stashed away so that the redirection can be
98 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
99 * standard output, and the standard error if it becomes a duplicate of
100 * stdout, is saved in memory.
101*
102 * We suppress interrupts so that we won't leave open file
103 * descriptors around.  Because the signal handler remains
104 * installed and we do not use system call restart, interrupts
105 * will still abort blocking opens such as fifos (they will fail
106 * with EINTR). There is, however, a race condition if an interrupt
107 * arrives after INTOFF and before open blocks.
108 */
109
110void
111redirect(union node *redir, int flags)
112{
113	union node *n;
114	struct redirtab *sv = NULL;
115	int i;
116	int fd;
117	char memory[10];	/* file descriptors to write to memory */
118
119	INTOFF;
120	for (i = 10 ; --i >= 0 ; )
121		memory[i] = 0;
122	memory[1] = flags & REDIR_BACKQ;
123	if (flags & REDIR_PUSH) {
124		empty_redirs++;
125		if (redir != NULL) {
126			sv = ckmalloc(sizeof (struct redirtab));
127			for (i = 0 ; i < 10 ; i++)
128				sv->renamed[i] = EMPTY;
129			sv->fd0_redirected = fd0_redirected;
130			sv->empty_redirs = empty_redirs - 1;
131			sv->next = redirlist;
132			redirlist = sv;
133			empty_redirs = 0;
134		}
135	}
136	for (n = redir ; n ; n = n->nfile.next) {
137		fd = n->nfile.fd;
138		if (fd == 0)
139			fd0_redirected = 1;
140		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
141		    n->ndup.dupfd == fd)
142			continue; /* redirect from/to same file descriptor */
143
144		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
145			INTOFF;
146			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
147				switch (errno) {
148				case EBADF:
149					i = CLOSED;
150					break;
151				default:
152					INTON;
153					error("%d: %s", fd, strerror(errno));
154					break;
155				}
156			}
157			sv->renamed[fd] = i;
158			INTON;
159		}
160		openredirect(n, memory);
161		INTON;
162		INTOFF;
163	}
164	if (memory[1])
165		out1 = &memout;
166	if (memory[2])
167		out2 = &memout;
168	INTON;
169}
170
171
172static void
173openredirect(union node *redir, char memory[10])
174{
175	struct stat sb;
176	int fd = redir->nfile.fd;
177	const char *fname;
178	int f;
179	int e;
180
181	memory[fd] = 0;
182	switch (redir->nfile.type) {
183	case NFROM:
184		fname = redir->nfile.expfname;
185		if ((f = open(fname, O_RDONLY)) < 0)
186			error("cannot open %s: %s", fname, strerror(errno));
187		break;
188	case NFROMTO:
189		fname = redir->nfile.expfname;
190		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
191			error("cannot create %s: %s", fname, strerror(errno));
192		break;
193	case NTO:
194		if (Cflag) {
195			fname = redir->nfile.expfname;
196			if (stat(fname, &sb) == -1) {
197				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
198					error("cannot create %s: %s", fname, strerror(errno));
199			} else if (!S_ISREG(sb.st_mode)) {
200				if ((f = open(fname, O_WRONLY, 0666)) < 0)
201					error("cannot create %s: %s", fname, strerror(errno));
202				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
203					close(f);
204					error("cannot create %s: %s", fname,
205					    strerror(EEXIST));
206				}
207			} else
208				error("cannot create %s: %s", fname,
209				    strerror(EEXIST));
210			break;
211		}
212		/* FALLTHROUGH */
213	case NCLOBBER:
214		fname = redir->nfile.expfname;
215		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
216			error("cannot create %s: %s", fname, strerror(errno));
217		break;
218	case NAPPEND:
219		fname = redir->nfile.expfname;
220		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
221			error("cannot create %s: %s", fname, strerror(errno));
222		break;
223	case NTOFD:
224	case NFROMFD:
225		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
226			if (memory[redir->ndup.dupfd])
227				memory[fd] = 1;
228			else {
229				if (dup2(redir->ndup.dupfd, fd) < 0)
230					error("%d: %s", redir->ndup.dupfd,
231							strerror(errno));
232			}
233		} else {
234			close(fd);
235		}
236		return;
237	case NHERE:
238	case NXHERE:
239		f = openhere(redir);
240		break;
241	default:
242		abort();
243	}
244	if (f != fd) {
245		if (dup2(f, fd) == -1) {
246			e = errno;
247			close(f);
248			error("%d: %s", fd, strerror(e));
249		}
250		close(f);
251	}
252}
253
254
255/*
256 * Handle here documents.  Normally we fork off a process to write the
257 * data to a pipe.  If the document is short, we can stuff the data in
258 * the pipe without forking.
259 */
260
261static int
262openhere(union node *redir)
263{
264	const char *p;
265	int pip[2];
266	size_t len = 0;
267	int flags;
268	ssize_t written = 0;
269
270	if (pipe(pip) < 0)
271		error("Pipe call failed: %s", strerror(errno));
272
273	if (redir->type == NXHERE)
274		p = redir->nhere.expdoc;
275	else
276		p = redir->nhere.doc->narg.text;
277	len = strlen(p);
278	if (len == 0)
279		goto out;
280	flags = fcntl(pip[1], F_GETFL, 0);
281	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
282		written = write(pip[1], p, len);
283		if (written < 0)
284			written = 0;
285		if ((size_t)written == len)
286			goto out;
287		fcntl(pip[1], F_SETFL, flags);
288	}
289
290	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
291		close(pip[0]);
292		signal(SIGINT, SIG_IGN);
293		signal(SIGQUIT, SIG_IGN);
294		signal(SIGHUP, SIG_IGN);
295		signal(SIGTSTP, SIG_IGN);
296		signal(SIGPIPE, SIG_DFL);
297		xwrite(pip[1], p + written, len - written);
298		_exit(0);
299	}
300out:
301	close(pip[1]);
302	return pip[0];
303}
304
305
306
307/*
308 * Undo the effects of the last redirection.
309 */
310
311void
312popredir(void)
313{
314	struct redirtab *rp = redirlist;
315	int i;
316
317	INTOFF;
318	if (empty_redirs > 0) {
319		empty_redirs--;
320		INTON;
321		return;
322	}
323	for (i = 0 ; i < 10 ; i++) {
324		if (rp->renamed[i] != EMPTY) {
325			if (rp->renamed[i] >= 0) {
326				dup2(rp->renamed[i], i);
327				close(rp->renamed[i]);
328			} else {
329				close(i);
330			}
331		}
332	}
333	fd0_redirected = rp->fd0_redirected;
334	empty_redirs = rp->empty_redirs;
335	redirlist = rp->next;
336	ckfree(rp);
337	INTON;
338}
339
340/* Return true if fd 0 has already been redirected at least once.  */
341int
342fd0_redirected_p(void)
343{
344        return fd0_redirected != 0;
345}
346
347/*
348 * Discard all saved file descriptors.
349 */
350
351void
352clearredir(void)
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			rp->renamed[i] = EMPTY;
363		}
364	}
365}
366