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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 1.5 2005/01/31 22:29:40 dillon Exp $
41 #include "namespace.h"
42 #include <sys/types.h>
49 #include "un-namespace.h"
50 #include "libc_private.h"
54 * Re-direct an existing, open (probably) file to some other file.
55 * ANSI is written such that the original file gets closed if at
56 * all possible, no matter what.
59 freopen(const char *file, const char *mode, FILE *fp)
62 int dflags, flags, isopen, oflags, sverrno, wantfd;
64 if ((flags = __sflags(mode, &oflags)) == 0) {
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 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
96 (oflags & O_ACCMODE)) {
102 if ((oflags ^ dflags) & O_APPEND) {
104 dflags |= oflags & O_APPEND;
105 if (fcntl(fp->_file, F_SETFL, dflags) < 0) {
113 if (oflags & O_TRUNC)
114 ftruncate(fp->_file, 0);
115 if (_fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET) < 0 &&
130 * There are actually programs that depend on being able to "freopen"
131 * descriptors that weren't originally open. Keep this from breaking.
132 * Remember whether the stream was open to begin with, and which file
133 * descriptor (if any) was associated with it. If it was attached to
134 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
135 * should work. This is unnecessary if it was not a Unix file.
137 if (fp->_flags == 0) {
138 fp->_flags = __SEOF; /* hold on to it */
142 /* flush the stream; ANSI doesn't require this. */
143 if (fp->_flags & __SWR)
145 /* if close is NULL, closing is a no-op, hence pointless */
146 isopen = fp->_close != NULL;
147 if ((wantfd = fp->_file) < 0 && isopen) {
148 (void) (*fp->_close)(fp->_cookie);
153 /* Get a new descriptor to refer to the new file. */
154 f = _open(file, oflags, DEFFILEMODE);
155 if (f < 0 && isopen) {
156 /* If out of fd's close the old one and try again. */
157 if (errno == ENFILE || errno == EMFILE) {
158 (void) (*fp->_close)(fp->_cookie);
160 f = _open(file, oflags, DEFFILEMODE);
167 * Finish closing fp. Even if the open succeeded above, we cannot
168 * keep fp->_base: it may be the wrong size. This loses the effect
169 * of any setbuffer calls, but stdio has always done this before.
172 (void) (*fp->_close)(fp->_cookie);
173 if (fp->_flags & __SMBF)
174 free((char *)fp->_bf._base);
178 fp->_bf._base = NULL;
188 if (f < 0) { /* did not get it after all */
189 fp->_flags = 0; /* set it free */
190 errno = sverrno; /* restore in case _close clobbered */
196 * If reopening something that was open before on a real file, try
197 * to maintain the descriptor. Various C library routines (perror)
198 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
200 if (wantfd >= 0 && f != wantfd) {
201 if (_dup2(f, wantfd) >= 0) {
211 fp->_write = __swrite;
213 fp->_close = __sclose;