redir.c revision 254426 
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 254426 2013-08-16 20:24:41Z 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
69struct redirtab {
70	struct redirtab *next;
71	int renamed[10];
72};
73
74
75static struct redirtab *redirlist;
76
77/*
78 * We keep track of whether or not fd0 has been redirected.  This is for
79 * background commands, where we want to redirect fd0 to /dev/null only
80 * if it hasn't already been redirected.
81*/
82static int fd0_redirected = 0;
83
84static void openredirect(union node *, char[10 ]);
85static int openhere(union node *);
86
87
88/*
89 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
90 * old file descriptors are stashed away so that the redirection can be
91 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
92 * standard output, and the standard error if it becomes a duplicate of
93 * stdout, is saved in memory.
94 */
95
96void
97redirect(union node *redir, int flags)
98{
99	union node *n;
100	struct redirtab *sv = NULL;
101	int i;
102	int fd;
103	char memory[10];	/* file descriptors to write to memory */
104
105	for (i = 10 ; --i >= 0 ; )
106		memory[i] = 0;
107	memory[1] = flags & REDIR_BACKQ;
108	if (flags & REDIR_PUSH) {
109		sv = ckmalloc(sizeof (struct redirtab));
110		for (i = 0 ; i < 10 ; i++)
111			sv->renamed[i] = EMPTY;
112		sv->next = redirlist;
113		redirlist = sv;
114	}
115	for (n = redir ; n ; n = n->nfile.next) {
116		fd = n->nfile.fd;
117		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
118		    n->ndup.dupfd == fd)
119			continue; /* redirect from/to same file descriptor */
120
121		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
122			INTOFF;
123			if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
124				switch (errno) {
125				case EBADF:
126					i = CLOSED;
127					break;
128				default:
129					INTON;
130					error("%d: %s", fd, strerror(errno));
131					break;
132				}
133			}
134			sv->renamed[fd] = i;
135			INTON;
136		}
137		if (fd == 0)
138			fd0_redirected++;
139		openredirect(n, memory);
140	}
141	if (memory[1])
142		out1 = &memout;
143	if (memory[2])
144		out2 = &memout;
145}
146
147
148static void
149openredirect(union node *redir, char memory[10])
150{
151	struct stat sb;
152	int fd = redir->nfile.fd;
153	char *fname;
154	int f;
155	int e;
156
157	/*
158	 * We suppress interrupts so that we won't leave open file
159	 * descriptors around.  Because the signal handler remains
160	 * installed and we do not use system call restart, interrupts
161	 * will still abort blocking opens such as fifos (they will fail
162	 * with EINTR). There is, however, a race condition if an interrupt
163	 * arrives after INTOFF and before open blocks.
164	 */
165	INTOFF;
166	memory[fd] = 0;
167	switch (redir->nfile.type) {
168	case NFROM:
169		fname = redir->nfile.expfname;
170		if ((f = open(fname, O_RDONLY)) < 0)
171			error("cannot open %s: %s", fname, strerror(errno));
172movefd:
173		if (f != fd) {
174			if (dup2(f, fd) == -1) {
175				e = errno;
176				close(f);
177				error("%d: %s", fd, strerror(e));
178			}
179			close(f);
180		}
181		break;
182	case NFROMTO:
183		fname = redir->nfile.expfname;
184		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
185			error("cannot create %s: %s", fname, strerror(errno));
186		goto movefd;
187	case NTO:
188		if (Cflag) {
189			fname = redir->nfile.expfname;
190			if (stat(fname, &sb) == -1) {
191				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
192					error("cannot create %s: %s", fname, strerror(errno));
193			} else if (!S_ISREG(sb.st_mode)) {
194				if ((f = open(fname, O_WRONLY, 0666)) < 0)
195					error("cannot create %s: %s", fname, strerror(errno));
196				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
197					close(f);
198					error("cannot create %s: %s", fname,
199					    strerror(EEXIST));
200				}
201			} else
202				error("cannot create %s: %s", fname,
203				    strerror(EEXIST));
204			goto movefd;
205		}
206		/* FALLTHROUGH */
207	case NCLOBBER:
208		fname = redir->nfile.expfname;
209		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
210			error("cannot create %s: %s", fname, strerror(errno));
211		goto movefd;
212	case NAPPEND:
213		fname = redir->nfile.expfname;
214		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
215			error("cannot create %s: %s", fname, strerror(errno));
216		goto movefd;
217	case NTOFD:
218	case NFROMFD:
219		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
220			if (memory[redir->ndup.dupfd])
221				memory[fd] = 1;
222			else {
223				if (dup2(redir->ndup.dupfd, fd) < 0)
224					error("%d: %s", redir->ndup.dupfd,
225							strerror(errno));
226			}
227		} else {
228			close(fd);
229		}
230		break;
231	case NHERE:
232	case NXHERE:
233		f = openhere(redir);
234		goto movefd;
235	default:
236		abort();
237	}
238	INTON;
239}
240
241
242/*
243 * Handle here documents.  Normally we fork off a process to write the
244 * data to a pipe.  If the document is short, we can stuff the data in
245 * the pipe without forking.
246 */
247
248static int
249openhere(union node *redir)
250{
251	char *p;
252	int pip[2];
253	size_t len = 0;
254	int flags;
255	ssize_t written = 0;
256
257	if (pipe(pip) < 0)
258		error("Pipe call failed: %s", strerror(errno));
259
260	if (redir->type == NXHERE)
261		p = redir->nhere.expdoc;
262	else
263		p = redir->nhere.doc->narg.text;
264	len = strlen(p);
265	if (len == 0)
266		goto out;
267	flags = fcntl(pip[1], F_GETFL, 0);
268	if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
269		written = write(pip[1], p, len);
270		if (written < 0)
271			written = 0;
272		if ((size_t)written == len)
273			goto out;
274		fcntl(pip[1], F_SETFL, flags);
275	}
276
277	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
278		close(pip[0]);
279		signal(SIGINT, SIG_IGN);
280		signal(SIGQUIT, SIG_IGN);
281		signal(SIGHUP, SIG_IGN);
282		signal(SIGTSTP, SIG_IGN);
283		signal(SIGPIPE, SIG_DFL);
284		xwrite(pip[1], p + written, len - written);
285		_exit(0);
286	}
287out:
288	close(pip[1]);
289	return pip[0];
290}
291
292
293
294/*
295 * Undo the effects of the last redirection.
296 */
297
298void
299popredir(void)
300{
301	struct redirtab *rp = redirlist;
302	int i;
303
304	for (i = 0 ; i < 10 ; i++) {
305		if (rp->renamed[i] != EMPTY) {
306                        if (i == 0)
307                                fd0_redirected--;
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	redirlist = rp->next;
318	ckfree(rp);
319	INTON;
320}
321
322/* Return true if fd 0 has already been redirected at least once.  */
323int
324fd0_redirected_p(void)
325{
326        return fd0_redirected != 0;
327}
328
329/*
330 * Discard all saved file descriptors.
331 */
332
333void
334clearredir(void)
335{
336	struct redirtab *rp;
337	int i;
338
339	for (rp = redirlist ; rp ; rp = rp->next) {
340		for (i = 0 ; i < 10 ; i++) {
341			if (rp->renamed[i] >= 0) {
342				close(rp->renamed[i]);
343			}
344			rp->renamed[i] = EMPTY;
345		}
346	}
347}
348