redir.c revision 11601 
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 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 *	$Id: redir.c,v 1.3 1995/05/30 00:07:22 rgrimes Exp $
37 */
38
39#ifndef lint
40static char sccsid[] = "@(#)redir.c	8.1 (Berkeley) 5/31/93";
41#endif /* not lint */
42
43/*
44 * Code for dealing with input/output redirection.
45 */
46
47#include "shell.h"
48#include "nodes.h"
49#include "jobs.h"
50#include "expand.h"
51#include "redir.h"
52#include "output.h"
53#include "memalloc.h"
54#include "error.h"
55#include <sys/types.h>
56#include <signal.h>
57#include <fcntl.h>
58#include <errno.h>
59#include <unistd.h>
60
61
62#define EMPTY -2		/* marks an unused slot in redirtab */
63#define PIPESIZE 4096		/* amount of buffering in a pipe */
64
65
66MKINIT
67struct redirtab {
68	struct redirtab *next;
69	short renamed[10];
70};
71
72
73MKINIT struct redirtab *redirlist;
74
75/*
76 * We keep track of whether or not fd0 has been redirected.  This is for
77 * background commands, where we want to redirect fd0 to /dev/null only
78 * if it hasn't already been redirected.
79*/
80int fd0_redirected = 0;
81
82#ifdef __STDC__
83STATIC void openredirect(union node *, char *);
84STATIC int openhere(union node *);
85#else
86STATIC void openredirect();
87STATIC int openhere();
88#endif
89
90
91
92/*
93 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
94 * old file descriptors are stashed away so that the redirection can be
95 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
96 * standard output, and the standard error if it becomes a duplicate of
97 * stdout, is saved in memory.
98 */
99
100void
101redirect(redir, flags)
102	union node *redir;
103	int flags;
104	{
105	union node *n;
106	struct redirtab *sv;
107	int i;
108	int fd;
109	char memory[10];		/* file descriptors to write to memory */
110
111	for (i = 10 ; --i >= 0 ; )
112		memory[i] = 0;
113	memory[1] = flags & REDIR_BACKQ;
114	if (flags & REDIR_PUSH) {
115		sv = ckmalloc(sizeof (struct redirtab));
116		for (i = 0 ; i < 10 ; i++)
117			sv->renamed[i] = EMPTY;
118		sv->next = redirlist;
119		redirlist = sv;
120	}
121	for (n = redir ; n ; n = n->nfile.next) {
122		fd = n->nfile.fd;
123		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
124		    n->ndup.dupfd == fd)
125			continue; /* redirect from/to myself */
126		if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
127			INTOFF;
128			if ((i = copyfd(fd, 10)) != EMPTY) {
129				sv->renamed[fd] = i;
130				close(fd);
131			}
132			INTON;
133			if (i == EMPTY)
134				error("Out of file descriptors");
135		} else {
136			close(fd);
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(redir, memory)
151	union node *redir;
152	char memory[10];
153	{
154	int fd = redir->nfile.fd;
155	char *fname;
156	int f;
157
158	/*
159	 * We suppress interrupts so that we won't leave open file
160	 * descriptors around.  This may not be such a good idea because
161	 * an open of a device or a fifo can block indefinitely.
162	 */
163	INTOFF;
164	memory[fd] = 0;
165	switch (redir->nfile.type) {
166	case NFROM:
167		fname = redir->nfile.expfname;
168		if ((f = open(fname, O_RDONLY)) < 0)
169			error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
170movefd:
171		if (f != fd) {
172			copyfd(f, fd);
173			close(f);
174		}
175		break;
176	case NTO:
177		fname = redir->nfile.expfname;
178#ifdef O_CREAT
179		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
180			error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
181#else
182		if ((f = creat(fname, 0666)) < 0)
183			error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
184#endif
185		goto movefd;
186	case NAPPEND:
187		fname = redir->nfile.expfname;
188#ifdef O_APPEND
189		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
190			error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
191#else
192		if ((f = open(fname, O_WRONLY)) < 0
193		 && (f = creat(fname, 0666)) < 0)
194			error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
195		lseek(f, (off_t)0, 2);
196#endif
197		goto movefd;
198	case NTOFD:
199	case NFROMFD:
200		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
201			if (memory[redir->ndup.dupfd])
202				memory[fd] = 1;
203			else
204				copyfd(redir->ndup.dupfd, fd);
205		}
206		break;
207	case NHERE:
208	case NXHERE:
209		f = openhere(redir);
210		goto movefd;
211	default:
212		abort();
213	}
214	INTON;
215}
216
217
218/*
219 * Handle here documents.  Normally we fork off a process to write the
220 * data to a pipe.  If the document is short, we can stuff the data in
221 * the pipe without forking.
222 */
223
224STATIC int
225openhere(redir)
226	union node *redir;
227	{
228	int pip[2];
229	int len;
230
231	if (pipe(pip) < 0)
232		error("Pipe call failed");
233	if (redir->type == NHERE) {
234		len = strlen(redir->nhere.doc->narg.text);
235		if (len <= PIPESIZE) {
236			xwrite(pip[1], redir->nhere.doc->narg.text, len);
237			goto out;
238		}
239	}
240	if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
241		close(pip[0]);
242		signal(SIGINT, SIG_IGN);
243		signal(SIGQUIT, SIG_IGN);
244		signal(SIGHUP, SIG_IGN);
245#ifdef SIGTSTP
246		signal(SIGTSTP, SIG_IGN);
247#endif
248		signal(SIGPIPE, SIG_DFL);
249		if (redir->type == NHERE)
250			xwrite(pip[1], redir->nhere.doc->narg.text, len);
251		else
252			expandhere(redir->nhere.doc, pip[1]);
253		_exit(0);
254	}
255out:
256	close(pip[1]);
257	return pip[0];
258}
259
260
261
262/*
263 * Undo the effects of the last redirection.
264 */
265
266void
267popredir() {
268	register struct redirtab *rp = redirlist;
269	int i;
270
271	for (i = 0 ; i < 10 ; i++) {
272		if (rp->renamed[i] != EMPTY) {
273                        if (i == 0)
274                                fd0_redirected--;
275			close(i);
276			if (rp->renamed[i] >= 0) {
277				copyfd(rp->renamed[i], i);
278				close(rp->renamed[i]);
279			}
280		}
281	}
282	INTOFF;
283	redirlist = rp->next;
284	ckfree(rp);
285	INTON;
286}
287
288/*
289 * Undo all redirections.  Called on error or interrupt.
290 */
291
292#ifdef mkinit
293
294INCLUDE "redir.h"
295
296RESET {
297	while (redirlist)
298		popredir();
299}
300
301SHELLPROC {
302	clearredir();
303}
304
305#endif
306
307/* Return true if fd 0 has already been redirected at least once.  */
308int
309fd0_redirected_p () {
310        return fd0_redirected != 0;
311}
312
313/*
314 * Discard all saved file descriptors.
315 */
316
317void
318clearredir() {
319	register struct redirtab *rp;
320	int i;
321
322	for (rp = redirlist ; rp ; rp = rp->next) {
323		for (i = 0 ; i < 10 ; i++) {
324			if (rp->renamed[i] >= 0) {
325				close(rp->renamed[i]);
326			}
327			rp->renamed[i] = EMPTY;
328		}
329	}
330}
331
332
333
334/*
335 * Copy a file descriptor to be >= to.  Returns -1
336 * if the source file descriptor is closed, EMPTY if there are no unused
337 * file descriptors left.
338 */
339
340int
341copyfd(from, to) {
342	int newfd;
343
344	newfd = fcntl(from, F_DUPFD, to);
345	if (newfd < 0 && errno == EMFILE)
346		return EMPTY;
347	if (newfd < 0)
348		error("%d: %s", from, strerror(errno));
349	return newfd;
350}
351