2 * Copyright (c) 1990, 1993
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5 * This code is derived from software contributed to Berkeley by
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36 * @(#)freopen.c 8.1 (Berkeley) 6/4/93
37 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $
38 * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
41 #include "namespace.h"
42 #include <sys/types.h>
49 #include "un-namespace.h"
51 #include "libc_private.h"
53 #include "priv_stdio.h"
56 * Re-direct an existing, open (probably) file to some other file.
57 * ANSI is written such that the original file gets closed if at
58 * all possible, no matter what.
61 freopen(const char *file, const char *mode, FILE *fp)
64 int dflags, flags, isopen, oflags, sverrno, wantfd;
66 if ((flags = __sflags(mode, &oflags)) == 0) {
79 * If the filename is a NULL pointer, the caller is asking us to
80 * re-open the same file with a different mode. We allow this only
81 * if the modes are compatible.
84 /* See comment below regarding freopen() of closed files. */
85 if (fp->pub._flags == 0) {
90 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) {
97 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
98 (oflags & O_ACCMODE)) {
104 if ((oflags ^ dflags) & O_APPEND) {
106 dflags |= oflags & O_APPEND;
107 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) {
115 if (oflags & O_TRUNC)
116 ftruncate(fp->pub._fileno, 0);
117 if (_fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET) < 0 &&
132 * There are actually programs that depend on being able to "freopen"
133 * descriptors that weren't originally open. Keep this from breaking.
134 * Remember whether the stream was open to begin with, and which file
135 * descriptor (if any) was associated with it. If it was attached to
136 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
137 * should work. This is unnecessary if it was not a Unix file.
139 if (fp->pub._flags == 0) {
140 fp->pub._flags = __SEOF; /* hold on to it */
144 /* flush the stream; ANSI doesn't require this. */
145 if (fp->pub._flags & __SWR)
147 /* if close is NULL, closing is a no-op, hence pointless */
148 isopen = fp->_close != NULL;
149 if ((wantfd = fp->pub._fileno) < 0 && isopen) {
150 (*fp->_close)(fp->_cookie);
155 /* Get a new descriptor to refer to the new file. */
156 f = _open(file, oflags, DEFFILEMODE);
157 if (f < 0 && isopen) {
158 /* If out of fd's close the old one and try again. */
159 if (errno == ENFILE || errno == EMFILE) {
160 (*fp->_close)(fp->_cookie);
162 f = _open(file, oflags, DEFFILEMODE);
169 * Finish closing fp. Even if the open succeeded above, we cannot
170 * keep fp->_base: it may be the wrong size. This loses the effect
171 * of any setbuffer calls, but stdio has always done this before.
174 (*fp->_close)(fp->_cookie);
175 if (fp->pub._flags & __SMBF)
176 free((char *)fp->_bf._base);
180 fp->_bf._base = NULL;
182 fp->pub._lbfsize = 0;
190 if (f < 0) { /* did not get it after all */
191 fp->pub._flags = 0; /* set it free */
192 errno = sverrno; /* restore in case _close clobbered */
198 * If reopening something that was open before on a real file, try
199 * to maintain the descriptor. Various C library routines (perror)
200 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
202 if (wantfd >= 0 && f != wantfd) {
203 if (_dup2(f, wantfd) >= 0) {
209 fp->pub._flags = flags;
213 fp->_write = __swrite;
215 fp->_close = __sclose;