redir.c revision 253650 
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 253650 2013-07-25 15:08:41Z 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
69MKINIT
70struct redirtab {
71	struct redirtab *next;
72	int renamed[10];
73};
74
75
76MKINIT 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->next = redirlist;
114		redirlist = sv;
115	}
116	for (n = redir ; n ; n = n->nfile.next) {
117		fd = n->nfile.fd;
118		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
119		    n->ndup.dupfd == fd)
120			continue; /* redirect from/to same file descriptor */
121
122		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
123			INTOFF;
124			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
125				switch (errno) {
126				case EBADF:
127					i = CLOSED;
128					break;
129				default:
130					INTON;
131					error("%d: %s", fd, strerror(errno));
132					break;
133				}
134			}
135			sv->renamed[fd] = i;
136			INTON;
137		}
138		if (fd == 0)
139			fd0_redirected++;
140		openredirect(n, memory);
141	}
142	if (memory[1])
143		out1 = &memout;
144	if (memory[2])
145		out2 = &memout;
146}
147
148
149static void
150openredirect(union node *redir, char memory[10])
151{
152	struct stat sb;
153	int fd = redir->nfile.fd;
154	char *fname;
155	int f;
156	int e;
157
158	/*
159	 * We suppress interrupts so that we won't leave open file
160	 * descriptors around.  Because the signal handler remains
161	 * installed and we do not use system call restart, interrupts
162	 * will still abort blocking opens such as fifos (they will fail
163	 * with EINTR). There is, however, a race condition if an interrupt
164	 * arrives after INTOFF and before open blocks.
165	 */
166	INTOFF;
167	memory[fd] = 0;
168	switch (redir->nfile.type) {
169	case NFROM:
170		fname = redir->nfile.expfname;
171		if ((f = open(fname, O_RDONLY)) < 0)
172			error("cannot open %s: %s", fname, strerror(errno));
173movefd:
174		if (f != fd) {
175			if (dup2(f, fd) == -1) {
176				e = errno;
177				close(f);
178				error("%d: %s", fd, strerror(e));
179			}
180			close(f);
181		}
182		break;
183	case NFROMTO:
184		fname = redir->nfile.expfname;
185		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
186			error("cannot create %s: %s", fname, strerror(errno));
187		goto movefd;
188	case NTO:
189		if (Cflag) {
190			fname = redir->nfile.expfname;
191			if (stat(fname, &sb) == -1) {
192				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
193					error("cannot create %s: %s", fname, strerror(errno));
194			} else if (!S_ISREG(sb.st_mode)) {
195				if ((f = open(fname, O_WRONLY, 0666)) < 0)
196					error("cannot create %s: %s", fname, strerror(errno));
197				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
198					close(f);
199					error("cannot create %s: %s", fname,
200					    strerror(EEXIST));
201				}
202			} else
203				error("cannot create %s: %s", fname,
204				    strerror(EEXIST));
205			goto movefd;
206		}
207		/* FALLTHROUGH */
208	case NCLOBBER:
209		fname = redir->nfile.expfname;
210		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
211			error("cannot create %s: %s", fname, strerror(errno));
212		goto movefd;
213	case NAPPEND:
214		fname = redir->nfile.expfname;
215		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
216			error("cannot create %s: %s", fname, strerror(errno));
217		goto movefd;
218	case NTOFD:
219	case NFROMFD:
220		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
221			if (memory[redir->ndup.dupfd])
222				memory[fd] = 1;
223			else {
224				if (dup2(redir->ndup.dupfd, fd) < 0)
225					error("%d: %s", redir->ndup.dupfd,
226							strerror(errno));
227			}
228		} else {
229			close(fd);
230		}
231		break;
232	case NHERE:
233	case NXHERE:
234		f = openhere(redir);
235		goto movefd;
236	default:
237		abort();
238	}
239	INTON;
240}
241
242
243/*
244 * Handle here documents.  Normally we fork off a process to write the
245 * data to a pipe.  If the document is short, we can stuff the data in
246 * the pipe without forking.
247 */
248
249static int
250openhere(union node *redir)
251{
252	char *p;
253	int pip[2];
254	size_t len = 0;
255	int flags;
256	ssize_t written = 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 == 0)
267		goto out;
268	flags = fcntl(pip[1], F_GETFL, 0);
269	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
270		written = write(pip[1], p, len);
271		if (written < 0)
272			written = 0;
273		if ((size_t)written == len)
274			goto out;
275		fcntl(pip[1], F_SETFL, flags);
276	}
277
278	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
279		close(pip[0]);
280		signal(SIGINT, SIG_IGN);
281		signal(SIGQUIT, SIG_IGN);
282		signal(SIGHUP, SIG_IGN);
283		signal(SIGTSTP, SIG_IGN);
284		signal(SIGPIPE, SIG_DFL);
285		xwrite(pip[1], p + written, len - written);
286		_exit(0);
287	}
288out:
289	close(pip[1]);
290	return pip[0];
291}
292
293
294
295/*
296 * Undo the effects of the last redirection.
297 */
298
299void
300popredir(void)
301{
302	struct redirtab *rp = redirlist;
303	int i;
304
305	for (i = 0 ; i < 10 ; i++) {
306		if (rp->renamed[i] != EMPTY) {
307                        if (i == 0)
308                                fd0_redirected--;
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	redirlist = rp->next;
319	ckfree(rp);
320	INTON;
321}
322
323/*
324 * Undo all redirections.  Called on error or interrupt.
325 */
326
327void
328resetredir(void)
329{
330	while (redirlist)
331		popredir();
332}
333
334
335/* Return true if fd 0 has already been redirected at least once.  */
336int
337fd0_redirected_p(void)
338{
339        return fd0_redirected != 0;
340}
341
342/*
343 * Discard all saved file descriptors.
344 */
345
346void
347clearredir(void)
348{
349	struct redirtab *rp;
350	int i;
351
352	for (rp = redirlist ; rp ; rp = rp->next) {
353		for (i = 0 ; i < 10 ; i++) {
354			if (rp->renamed[i] >= 0) {
355				close(rp->renamed[i]);
356			}
357			rp->renamed[i] = EMPTY;
358		}
359	}
360}
361