redir.c revision 199660 
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 199660 2009-11-22 18:23:30Z 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 PIPESIZE 4096		/* amount of buffering in a pipe */
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	int try;
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		try = 0;
120		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
121		    n->ndup.dupfd == fd)
122			continue; /* redirect from/to same file descriptor */
123
124		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
125			INTOFF;
126again:
127			if ((i = fcntl(fd, F_DUPFD, 10)) == -1) {
128				switch (errno) {
129				case EBADF:
130					if (!try) {
131						openredirect(n, memory);
132						try++;
133						goto again;
134					}
135					/* FALLTHROUGH*/
136				default:
137					INTON;
138					error("%d: %s", fd, strerror(errno));
139					break;
140				}
141			}
142			if (!try) {
143				sv->renamed[fd] = i;
144			}
145			INTON;
146		}
147		if (fd == 0)
148			fd0_redirected++;
149		if (!try)
150			openredirect(n, memory);
151	}
152	if (memory[1])
153		out1 = &memout;
154	if (memory[2])
155		out2 = &memout;
156}
157
158
159STATIC void
160openredirect(union node *redir, char memory[10])
161{
162	struct stat sb;
163	int fd = redir->nfile.fd;
164	char *fname;
165	int f;
166
167	/*
168	 * We suppress interrupts so that we won't leave open file
169	 * descriptors around.  Because the signal handler remains
170	 * installed and we do not use system call restart, interrupts
171	 * will still abort blocking opens such as fifos (they will fail
172	 * with EINTR). There is, however, a race condition if an interrupt
173	 * arrives after INTOFF and before open blocks.
174	 */
175	INTOFF;
176	memory[fd] = 0;
177	switch (redir->nfile.type) {
178	case NFROM:
179		fname = redir->nfile.expfname;
180		if ((f = open(fname, O_RDONLY)) < 0)
181			error("cannot open %s: %s", fname, strerror(errno));
182movefd:
183		if (f != fd) {
184			dup2(f, fd);
185			close(f);
186		}
187		break;
188	case NFROMTO:
189		fname = redir->nfile.expfname;
190		if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
191			error("cannot create %s: %s", fname, strerror(errno));
192		goto movefd;
193	case NTO:
194		if (Cflag) {
195			fname = redir->nfile.expfname;
196			if (stat(fname, &sb) == -1) {
197				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
198					error("cannot create %s: %s", fname, strerror(errno));
199			} else if (!S_ISREG(sb.st_mode)) {
200				if ((f = open(fname, O_WRONLY, 0666)) < 0)
201					error("cannot create %s: %s", fname, strerror(errno));
202				if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
203					close(f);
204					error("cannot create %s: %s", fname,
205					    strerror(EEXIST));
206				}
207			} else
208				error("cannot create %s: %s", fname,
209				    strerror(EEXIST));
210			goto movefd;
211		}
212		/* FALLTHROUGH */
213	case NCLOBBER:
214		fname = redir->nfile.expfname;
215		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
216			error("cannot create %s: %s", fname, strerror(errno));
217		goto movefd;
218	case NAPPEND:
219		fname = redir->nfile.expfname;
220		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
221			error("cannot create %s: %s", fname, strerror(errno));
222		goto movefd;
223	case NTOFD:
224	case NFROMFD:
225		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
226			if (memory[redir->ndup.dupfd])
227				memory[fd] = 1;
228			else
229				dup2(redir->ndup.dupfd, fd);
230		} else {
231			close(fd);
232		}
233		break;
234	case NHERE:
235	case NXHERE:
236		f = openhere(redir);
237		goto movefd;
238	default:
239		abort();
240	}
241	INTON;
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	int pip[2];
255	int len = 0;
256
257	if (pipe(pip) < 0)
258		error("Pipe call failed: %s", strerror(errno));
259	if (redir->type == NHERE) {
260		len = strlen(redir->nhere.doc->narg.text);
261		if (len <= PIPESIZE) {
262			xwrite(pip[1], redir->nhere.doc->narg.text, len);
263			goto out;
264		}
265	}
266	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
267		close(pip[0]);
268		signal(SIGINT, SIG_IGN);
269		signal(SIGQUIT, SIG_IGN);
270		signal(SIGHUP, SIG_IGN);
271		signal(SIGTSTP, SIG_IGN);
272		signal(SIGPIPE, SIG_DFL);
273		if (redir->type == NHERE)
274			xwrite(pip[1], redir->nhere.doc->narg.text, len);
275		else
276			expandhere(redir->nhere.doc, pip[1]);
277		_exit(0);
278	}
279out:
280	close(pip[1]);
281	return pip[0];
282}
283
284
285
286/*
287 * Undo the effects of the last redirection.
288 */
289
290void
291popredir(void)
292{
293	struct redirtab *rp = redirlist;
294	int i;
295
296	for (i = 0 ; i < 10 ; i++) {
297		if (rp->renamed[i] != EMPTY) {
298                        if (i == 0)
299                                fd0_redirected--;
300			if (rp->renamed[i] >= 0) {
301				dup2(rp->renamed[i], i);
302				close(rp->renamed[i]);
303			} else {
304				close(i);
305			}
306		}
307	}
308	INTOFF;
309	redirlist = rp->next;
310	ckfree(rp);
311	INTON;
312}
313
314/*
315 * Undo all redirections.  Called on error or interrupt.
316 */
317
318#ifdef mkinit
319
320INCLUDE "redir.h"
321
322RESET {
323	while (redirlist)
324		popredir();
325}
326
327SHELLPROC {
328	clearredir();
329}
330
331#endif
332
333/* Return true if fd 0 has already been redirected at least once.  */
334int
335fd0_redirected_p(void)
336{
337        return fd0_redirected != 0;
338}
339
340/*
341 * Discard all saved file descriptors.
342 */
343
344void
345clearredir(void)
346{
347	struct redirtab *rp;
348	int i;
349
350	for (rp = redirlist ; rp ; rp = rp->next) {
351		for (i = 0 ; i < 10 ; i++) {
352			if (rp->renamed[i] >= 0) {
353				close(rp->renamed[i]);
354			}
355			rp->renamed[i] = EMPTY;
356		}
357	}
358}
359