redir.c revision 213811 
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 213811 2010-10-13 22:18:03Z obrien $");
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#define PIPESIZE 4096		/* amount of buffering in a pipe */
68
69
70MKINIT
71struct redirtab {
72	struct redirtab *next;
73	int renamed[10];
74};
75
76
77MKINIT struct redirtab *redirlist;
78
79/*
80 * We keep track of whether or not fd0 has been redirected.  This is for
81 * background commands, where we want to redirect fd0 to /dev/null only
82 * if it hasn't already been redirected.
83*/
84static int fd0_redirected = 0;
85
86static void openredirect(union node *, char[10 ]);
87static int openhere(union node *);
88
89
90/*
91 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
92 * old file descriptors are stashed away so that the redirection can be
93 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
94 * standard output, and the standard error if it becomes a duplicate of
95 * stdout, is saved in memory.
96 */
97
98void
99redirect(union node *redir, int flags)
100{
101	union node *n;
102	struct redirtab *sv = NULL;
103	int i;
104	int fd;
105	char memory[10];	/* file descriptors to write to memory */
106
107	for (i = 10 ; --i >= 0 ; )
108		memory[i] = 0;
109	memory[1] = flags & REDIR_BACKQ;
110	if (flags & REDIR_PUSH) {
111		sv = ckmalloc(sizeof (struct redirtab));
112		for (i = 0 ; i < 10 ; i++)
113			sv->renamed[i] = EMPTY;
114		sv->next = redirlist;
115		redirlist = sv;
116	}
117	for (n = redir ; n ; n = n->nfile.next) {
118		fd = n->nfile.fd;
119		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
120		    n->ndup.dupfd == fd)
121			continue; /* redirect from/to same file descriptor */
122
123		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
124			INTOFF;
125			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
126				switch (errno) {
127				case EBADF:
128					i = CLOSED;
129					break;
130				default:
131					INTON;
132					error("%d: %s", fd, strerror(errno));
133					break;
134				}
135			} else
136				(void)fcntl(i, F_SETFD, FD_CLOEXEC);
137			sv->renamed[fd] = i;
138			INTON;
139		}
140		if (fd == 0)
141			fd0_redirected++;
142		openredirect(n, memory);
143	}
144	if (memory[1])
145		out1 = &memout;
146	if (memory[2])
147		out2 = &memout;
148}
149
150
151static void
152openredirect(union node *redir, char memory[10])
153{
154	struct stat sb;
155	int fd = redir->nfile.fd;
156	char *fname;
157	int f;
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			dup2(f, fd);
177			close(f);
178		}
179		break;
180	case NFROMTO:
181		fname = redir->nfile.expfname;
182		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
183			error("cannot create %s: %s", fname, strerror(errno));
184		goto movefd;
185	case NTO:
186		if (Cflag) {
187			fname = redir->nfile.expfname;
188			if (stat(fname, &sb) == -1) {
189				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
190					error("cannot create %s: %s", fname, strerror(errno));
191			} else if (!S_ISREG(sb.st_mode)) {
192				if ((f = open(fname, O_WRONLY, 0666)) < 0)
193					error("cannot create %s: %s", fname, strerror(errno));
194				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
195					close(f);
196					error("cannot create %s: %s", fname,
197					    strerror(EEXIST));
198				}
199			} else
200				error("cannot create %s: %s", fname,
201				    strerror(EEXIST));
202			goto movefd;
203		}
204		/* FALLTHROUGH */
205	case NCLOBBER:
206		fname = redir->nfile.expfname;
207		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
208			error("cannot create %s: %s", fname, strerror(errno));
209		goto movefd;
210	case NAPPEND:
211		fname = redir->nfile.expfname;
212		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
213			error("cannot create %s: %s", fname, strerror(errno));
214		goto movefd;
215	case NTOFD:
216	case NFROMFD:
217		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
218			if (memory[redir->ndup.dupfd])
219				memory[fd] = 1;
220			else
221				dup2(redir->ndup.dupfd, fd);
222		} else {
223			close(fd);
224		}
225		break;
226	case NHERE:
227	case NXHERE:
228		f = openhere(redir);
229		goto movefd;
230	default:
231		abort();
232	}
233	INTON;
234}
235
236
237/*
238 * Handle here documents.  Normally we fork off a process to write the
239 * data to a pipe.  If the document is short, we can stuff the data in
240 * the pipe without forking.
241 */
242
243static int
244openhere(union node *redir)
245{
246	int pip[2];
247	int len = 0;
248
249	if (pipe(pip) < 0)
250		error("Pipe call failed: %s", strerror(errno));
251	if (redir->type == NHERE) {
252		len = strlen(redir->nhere.doc->narg.text);
253		if (len <= PIPESIZE) {
254			xwrite(pip[1], redir->nhere.doc->narg.text, len);
255			goto out;
256		}
257	}
258	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
259		close(pip[0]);
260		signal(SIGINT, SIG_IGN);
261		signal(SIGQUIT, SIG_IGN);
262		signal(SIGHUP, SIG_IGN);
263		signal(SIGTSTP, SIG_IGN);
264		signal(SIGPIPE, SIG_DFL);
265		if (redir->type == NHERE)
266			xwrite(pip[1], redir->nhere.doc->narg.text, len);
267		else
268			expandhere(redir->nhere.doc, pip[1]);
269		_exit(0);
270	}
271out:
272	close(pip[1]);
273	return pip[0];
274}
275
276
277
278/*
279 * Undo the effects of the last redirection.
280 */
281
282void
283popredir(void)
284{
285	struct redirtab *rp = redirlist;
286	int i;
287
288	for (i = 0 ; i < 10 ; i++) {
289		if (rp->renamed[i] != EMPTY) {
290                        if (i == 0)
291                                fd0_redirected--;
292			if (rp->renamed[i] >= 0) {
293				dup2(rp->renamed[i], i);
294				close(rp->renamed[i]);
295			} else {
296				close(i);
297			}
298		}
299	}
300	INTOFF;
301	redirlist = rp->next;
302	ckfree(rp);
303	INTON;
304}
305
306/*
307 * Undo all redirections.  Called on error or interrupt.
308 */
309
310#ifdef mkinit
311
312INCLUDE "redir.h"
313
314RESET {
315	while (redirlist)
316		popredir();
317}
318
319SHELLPROC {
320	clearredir();
321}
322
323#endif
324
325/* Return true if fd 0 has already been redirected at least once.  */
326int
327fd0_redirected_p(void)
328{
329        return fd0_redirected != 0;
330}
331
332/*
333 * Discard all saved file descriptors.
334 */
335
336void
337clearredir(void)
338{
339	struct redirtab *rp;
340	int i;
341
342	for (rp = redirlist ; rp ; rp = rp->next) {
343		for (i = 0 ; i < 10 ; i++) {
344			if (rp->renamed[i] >= 0) {
345				close(rp->renamed[i]);
346			}
347			rp->renamed[i] = EMPTY;
348		}
349	}
350}
351