redir.c revision 264478 
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 264478 2014-04-14 21:26:34Z 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 * We suppress interrupts so that we won't leave open file
97 * descriptors around.  Because the signal handler remains
98 * installed and we do not use system call restart, interrupts
99 * will still abort blocking opens such as fifos (they will fail
100 * with EINTR). There is, however, a race condition if an interrupt
101 * arrives after INTOFF and before open blocks.
102 */
103
104void
105redirect(union node *redir, int flags)
106{
107	union node *n;
108	struct redirtab *sv = NULL;
109	int i;
110	int fd;
111	char memory[10];	/* file descriptors to write to memory */
112
113	INTOFF;
114	for (i = 10 ; --i >= 0 ; )
115		memory[i] = 0;
116	memory[1] = flags & REDIR_BACKQ;
117	if (flags & REDIR_PUSH) {
118		sv = ckmalloc(sizeof (struct redirtab));
119		for (i = 0 ; i < 10 ; i++)
120			sv->renamed[i] = EMPTY;
121		sv->fd0_redirected = fd0_redirected;
122		sv->next = redirlist;
123		redirlist = sv;
124	}
125	for (n = redir ; n ; n = n->nfile.next) {
126		fd = n->nfile.fd;
127		if (fd == 0)
128			fd0_redirected = 1;
129		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
130		    n->ndup.dupfd == fd)
131			continue; /* redirect from/to same file descriptor */
132
133		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
134			INTOFF;
135			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
136				switch (errno) {
137				case EBADF:
138					i = CLOSED;
139					break;
140				default:
141					INTON;
142					error("%d: %s", fd, strerror(errno));
143					break;
144				}
145			}
146			sv->renamed[fd] = i;
147			INTON;
148		}
149		openredirect(n, memory);
150		INTON;
151		INTOFF;
152	}
153	if (memory[1])
154		out1 = &memout;
155	if (memory[2])
156		out2 = &memout;
157	INTON;
158}
159
160
161static void
162openredirect(union node *redir, char memory[10])
163{
164	struct stat sb;
165	int fd = redir->nfile.fd;
166	const char *fname;
167	int f;
168	int e;
169
170	memory[fd] = 0;
171	switch (redir->nfile.type) {
172	case NFROM:
173		fname = redir->nfile.expfname;
174		if ((f = open(fname, O_RDONLY)) < 0)
175			error("cannot open %s: %s", fname, strerror(errno));
176movefd:
177		if (f != fd) {
178			if (dup2(f, fd) == -1) {
179				e = errno;
180				close(f);
181				error("%d: %s", fd, strerror(e));
182			}
183			close(f);
184		}
185		break;
186	case NFROMTO:
187		fname = redir->nfile.expfname;
188		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
189			error("cannot create %s: %s", fname, strerror(errno));
190		goto movefd;
191	case NTO:
192		if (Cflag) {
193			fname = redir->nfile.expfname;
194			if (stat(fname, &sb) == -1) {
195				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
196					error("cannot create %s: %s", fname, strerror(errno));
197			} else if (!S_ISREG(sb.st_mode)) {
198				if ((f = open(fname, O_WRONLY, 0666)) < 0)
199					error("cannot create %s: %s", fname, strerror(errno));
200				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
201					close(f);
202					error("cannot create %s: %s", fname,
203					    strerror(EEXIST));
204				}
205			} else
206				error("cannot create %s: %s", fname,
207				    strerror(EEXIST));
208			goto movefd;
209		}
210		/* FALLTHROUGH */
211	case NCLOBBER:
212		fname = redir->nfile.expfname;
213		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
214			error("cannot create %s: %s", fname, strerror(errno));
215		goto movefd;
216	case NAPPEND:
217		fname = redir->nfile.expfname;
218		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
219			error("cannot create %s: %s", fname, strerror(errno));
220		goto movefd;
221	case NTOFD:
222	case NFROMFD:
223		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
224			if (memory[redir->ndup.dupfd])
225				memory[fd] = 1;
226			else {
227				if (dup2(redir->ndup.dupfd, fd) < 0)
228					error("%d: %s", redir->ndup.dupfd,
229							strerror(errno));
230			}
231		} else {
232			close(fd);
233		}
234		break;
235	case NHERE:
236	case NXHERE:
237		f = openhere(redir);
238		goto movefd;
239	default:
240		abort();
241	}
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	const char *p;
255	int pip[2];
256	size_t len = 0;
257	int flags;
258	ssize_t written = 0;
259
260	if (pipe(pip) < 0)
261		error("Pipe call failed: %s", strerror(errno));
262
263	if (redir->type == NXHERE)
264		p = redir->nhere.expdoc;
265	else
266		p = redir->nhere.doc->narg.text;
267	len = strlen(p);
268	if (len == 0)
269		goto out;
270	flags = fcntl(pip[1], F_GETFL, 0);
271	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
272		written = write(pip[1], p, len);
273		if (written < 0)
274			written = 0;
275		if ((size_t)written == len)
276			goto out;
277		fcntl(pip[1], F_SETFL, flags);
278	}
279
280	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
281		close(pip[0]);
282		signal(SIGINT, SIG_IGN);
283		signal(SIGQUIT, SIG_IGN);
284		signal(SIGHUP, SIG_IGN);
285		signal(SIGTSTP, SIG_IGN);
286		signal(SIGPIPE, SIG_DFL);
287		xwrite(pip[1], p + written, len - written);
288		_exit(0);
289	}
290out:
291	close(pip[1]);
292	return pip[0];
293}
294
295
296
297/*
298 * Undo the effects of the last redirection.
299 */
300
301void
302popredir(void)
303{
304	struct redirtab *rp = redirlist;
305	int i;
306
307	for (i = 0 ; i < 10 ; i++) {
308		if (rp->renamed[i] != EMPTY) {
309			if (rp->renamed[i] >= 0) {
310				dup2(rp->renamed[i], i);
311				close(rp->renamed[i]);
312			} else {
313				close(i);
314			}
315		}
316	}
317	INTOFF;
318	fd0_redirected = rp->fd0_redirected;
319	redirlist = rp->next;
320	ckfree(rp);
321	INTON;
322}
323
324/* Return true if fd 0 has already been redirected at least once.  */
325int
326fd0_redirected_p(void)
327{
328        return fd0_redirected != 0;
329}
330
331/*
332 * Discard all saved file descriptors.
333 */
334
335void
336clearredir(void)
337{
338	struct redirtab *rp;
339	int i;
340
341	for (rp = redirlist ; rp ; rp = rp->next) {
342		for (i = 0 ; i < 10 ; i++) {
343			if (rp->renamed[i] >= 0) {
344				close(rp->renamed[i]);
345			}
346			rp->renamed[i] = EMPTY;
347		}
348	}
349}
350