redir.c revision 264168 
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: stable/10/bin/sh/redir.c 264168 2014-04-05 20:01:08Z 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
68
69struct redirtab {
70	struct redirtab *next;
71	int renamed[10];
72	int fd0_redirected;
73};
74
75
76static struct redirtab *redirlist;
77
78/*
79 * We keep track of whether or not fd0 has been redirected.  This is for
80 * background commands, where we want to redirect fd0 to /dev/null only
81 * if it hasn't already been redirected.
82*/
83static int fd0_redirected = 0;
84
85static void openredirect(union node *, char[10 ]);
86static int openhere(union node *);
87
88
89/*
90 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
91 * old file descriptors are stashed away so that the redirection can be
92 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
93 * standard output, and the standard error if it becomes a duplicate of
94 * stdout, is saved in memory.
95 */
96
97void
98redirect(union node *redir, int flags)
99{
100	union node *n;
101	struct redirtab *sv = NULL;
102	int i;
103	int fd;
104	char memory[10];	/* file descriptors to write to memory */
105
106	for (i = 10 ; --i >= 0 ; )
107		memory[i] = 0;
108	memory[1] = flags & REDIR_BACKQ;
109	if (flags & REDIR_PUSH) {
110		sv = ckmalloc(sizeof (struct redirtab));
111		for (i = 0 ; i < 10 ; i++)
112			sv->renamed[i] = EMPTY;
113		sv->fd0_redirected = fd0_redirected;
114		sv->next = redirlist;
115		redirlist = sv;
116	}
117	for (n = redir ; n ; n = n->nfile.next) {
118		fd = n->nfile.fd;
119		if (fd == 0)
120			fd0_redirected = 1;
121		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
122		    n->ndup.dupfd == fd)
123			continue; /* redirect from/to same file descriptor */
124
125		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
126			INTOFF;
127			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
128				switch (errno) {
129				case EBADF:
130					i = CLOSED;
131					break;
132				default:
133					INTON;
134					error("%d: %s", fd, strerror(errno));
135					break;
136				}
137			}
138			sv->renamed[fd] = i;
139			INTON;
140		}
141		openredirect(n, memory);
142	}
143	if (memory[1])
144		out1 = &memout;
145	if (memory[2])
146		out2 = &memout;
147}
148
149
150static void
151openredirect(union node *redir, char memory[10])
152{
153	struct stat sb;
154	int fd = redir->nfile.fd;
155	const char *fname;
156	int f;
157	int e;
158
159	/*
160	 * We suppress interrupts so that we won't leave open file
161	 * descriptors around.  Because the signal handler remains
162	 * installed and we do not use system call restart, interrupts
163	 * will still abort blocking opens such as fifos (they will fail
164	 * with EINTR). There is, however, a race condition if an interrupt
165	 * arrives after INTOFF and before open blocks.
166	 */
167	INTOFF;
168	memory[fd] = 0;
169	switch (redir->nfile.type) {
170	case NFROM:
171		fname = redir->nfile.expfname;
172		if ((f = open(fname, O_RDONLY)) < 0)
173			error("cannot open %s: %s", fname, strerror(errno));
174movefd:
175		if (f != fd) {
176			if (dup2(f, fd) == -1) {
177				e = errno;
178				close(f);
179				error("%d: %s", fd, strerror(e));
180			}
181			close(f);
182		}
183		break;
184	case NFROMTO:
185		fname = redir->nfile.expfname;
186		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
187			error("cannot create %s: %s", fname, strerror(errno));
188		goto movefd;
189	case NTO:
190		if (Cflag) {
191			fname = redir->nfile.expfname;
192			if (stat(fname, &sb) == -1) {
193				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
194					error("cannot create %s: %s", fname, strerror(errno));
195			} else if (!S_ISREG(sb.st_mode)) {
196				if ((f = open(fname, O_WRONLY, 0666)) < 0)
197					error("cannot create %s: %s", fname, strerror(errno));
198				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
199					close(f);
200					error("cannot create %s: %s", fname,
201					    strerror(EEXIST));
202				}
203			} else
204				error("cannot create %s: %s", fname,
205				    strerror(EEXIST));
206			goto movefd;
207		}
208		/* FALLTHROUGH */
209	case NCLOBBER:
210		fname = redir->nfile.expfname;
211		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
212			error("cannot create %s: %s", fname, strerror(errno));
213		goto movefd;
214	case NAPPEND:
215		fname = redir->nfile.expfname;
216		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
217			error("cannot create %s: %s", fname, strerror(errno));
218		goto movefd;
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				if (dup2(redir->ndup.dupfd, fd) < 0)
226					error("%d: %s", redir->ndup.dupfd,
227							strerror(errno));
228			}
229		} else {
230			close(fd);
231		}
232		break;
233	case NHERE:
234	case NXHERE:
235		f = openhere(redir);
236		goto movefd;
237	default:
238		abort();
239	}
240	INTON;
241}
242
243
244/*
245 * Handle here documents.  Normally we fork off a process to write the
246 * data to a pipe.  If the document is short, we can stuff the data in
247 * the pipe without forking.
248 */
249
250static int
251openhere(union node *redir)
252{
253	const char *p;
254	int pip[2];
255	size_t len = 0;
256	int flags;
257	ssize_t written = 0;
258
259	if (pipe(pip) < 0)
260		error("Pipe call failed: %s", strerror(errno));
261
262	if (redir->type == NXHERE)
263		p = redir->nhere.expdoc;
264	else
265		p = redir->nhere.doc->narg.text;
266	len = strlen(p);
267	if (len == 0)
268		goto out;
269	flags = fcntl(pip[1], F_GETFL, 0);
270	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
271		written = write(pip[1], p, len);
272		if (written < 0)
273			written = 0;
274		if ((size_t)written == len)
275			goto out;
276		fcntl(pip[1], F_SETFL, flags);
277	}
278
279	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
280		close(pip[0]);
281		signal(SIGINT, SIG_IGN);
282		signal(SIGQUIT, SIG_IGN);
283		signal(SIGHUP, SIG_IGN);
284		signal(SIGTSTP, SIG_IGN);
285		signal(SIGPIPE, SIG_DFL);
286		xwrite(pip[1], p + written, len - written);
287		_exit(0);
288	}
289out:
290	close(pip[1]);
291	return pip[0];
292}
293
294
295
296/*
297 * Undo the effects of the last redirection.
298 */
299
300void
301popredir(void)
302{
303	struct redirtab *rp = redirlist;
304	int i;
305
306	for (i = 0 ; i < 10 ; i++) {
307		if (rp->renamed[i] != EMPTY) {
308			if (rp->renamed[i] >= 0) {
309				dup2(rp->renamed[i], i);
310				close(rp->renamed[i]);
311			} else {
312				close(i);
313			}
314		}
315	}
316	INTOFF;
317	fd0_redirected = rp->fd0_redirected;
318	redirlist = rp->next;
319	ckfree(rp);
320	INTON;
321}
322
323/* Return true if fd 0 has already been redirected at least once.  */
324int
325fd0_redirected_p(void)
326{
327        return fd0_redirected != 0;
328}
329
330/*
331 * Discard all saved file descriptors.
332 */
333
334void
335clearredir(void)
336{
337	struct redirtab *rp;
338	int i;
339
340	for (rp = redirlist ; rp ; rp = rp->next) {
341		for (i = 0 ; i < 10 ; i++) {
342			if (rp->renamed[i] >= 0) {
343				close(rp->renamed[i]);
344			}
345			rp->renamed[i] = EMPTY;
346		}
347	}
348}
349