2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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. 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.
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
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29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
39 #include "namespace.h"
40 #include <sys/types.h>
48 #include "un-namespace.h"
49 #include "libc_private.h"
53 * Re-direct an existing, open (probably) file to some other file.
54 * ANSI is written such that the original file gets closed if at
55 * all possible, no matter what.
58 freopen(const char * __restrict file, const char * __restrict mode,
62 int dflags, flags, isopen, oflags, sverrno, wantfd;
64 if ((flags = __sflags(mode, &oflags)) == 0) {
71 FLOCKFILE_CANCELSAFE(fp);
77 * If the filename is a NULL pointer, the caller is asking us to
78 * re-open the same file with a different mode. We allow this only
79 * if the modes are compatible.
82 /* See comment below regarding freopen() of closed files. */
83 if (fp->_flags == 0) {
88 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
95 /* Work around incorrect O_ACCMODE. */
96 if ((dflags & O_ACCMODE) != O_RDWR &&
97 (dflags & (O_ACCMODE | O_EXEC)) != (oflags & O_ACCMODE)) {
103 if (fp->_flags & __SWR)
105 if ((oflags ^ dflags) & O_APPEND) {
107 dflags |= oflags & O_APPEND;
108 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
116 if (oflags & O_TRUNC)
117 (void) ftruncate(fp->_file, (off_t)0);
118 if (!(oflags & O_APPEND))
119 (void) _sseek(fp, (fpos_t)0, SEEK_SET);
120 if (oflags & O_CLOEXEC)
121 (void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC);
129 * There are actually programs that depend on being able to "freopen"
130 * descriptors that weren't originally open. Keep this from breaking.
131 * Remember whether the stream was open to begin with, and which file
132 * descriptor (if any) was associated with it. If it was attached to
133 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
134 * should work. This is unnecessary if it was not a Unix file.
136 if (fp->_flags == 0) {
137 fp->_flags = __SEOF; /* hold on to it */
141 /* flush the stream; ANSI doesn't require this. */
142 if (fp->_flags & __SWR)
144 /* if close is NULL, closing is a no-op, hence pointless */
145 isopen = fp->_close != NULL;
146 if ((wantfd = fp->_file) < 0 && isopen) {
147 (void) (*fp->_close)(fp->_cookie);
152 /* Get a new descriptor to refer to the new file. */
153 f = _open(file, oflags, DEFFILEMODE);
154 /* If out of fd's close the old one and try again. */
155 if (f < 0 && isopen && wantfd > STDERR_FILENO &&
156 (errno == ENFILE || errno == EMFILE)) {
157 (void) (*fp->_close)(fp->_cookie);
160 f = _open(file, oflags, DEFFILEMODE);
166 * Finish closing fp. Even if the open succeeded above, we cannot
167 * keep fp->_base: it may be the wrong size. This loses the effect
168 * of any setbuffer calls, but stdio has always done this before.
170 * Leave the existing file descriptor open until dup2() is called
171 * below to avoid races where a concurrent open() in another thread
172 * could claim the existing descriptor.
174 if (fp->_flags & __SMBF)
175 free((char *)fp->_bf._base);
179 fp->_bf._base = NULL;
188 fp->_orientation = 0;
189 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
192 if (f < 0) { /* did not get it after all */
194 (void) (*fp->_close)(fp->_cookie);
195 fp->_flags = 0; /* set it free */
196 errno = sverrno; /* restore in case _close clobbered */
202 * If reopening something that was open before on a real file, try
203 * to maintain the descriptor. Various C library routines (perror)
204 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
207 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) :
208 _dup2(f, wantfd)) >= 0) {
212 (void)_close(fp->_file);
216 * File descriptors are a full int, but _file is only a short.
217 * If we get a valid file descriptor that is greater than
218 * SHRT_MAX, then the fd will get sign-extended into an
219 * invalid file descriptor. Handle this case by failing the
223 fp->_flags = 0; /* set it free */
233 fp->_write = __swrite;
235 fp->_close = __sclose;
237 * When opening in append mode, even though we use O_APPEND,
238 * we need to seek to the end so that ftell() gets the right
239 * answer. If the user then alters the seek pointer, or
240 * the file extends, this will fail, but there is not much
241 * we can do about this. (We could set __SAPP and check in
244 if (oflags & O_APPEND) {
245 fp->_flags2 |= __S2OAP;
246 (void) _sseek(fp, (fpos_t)0, SEEK_END);
249 FUNLOCKFILE_CANCELSAFE();