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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 1.3 2004/06/07 20:35:41 hmp Exp $
41 #include <sys/types.h>
48 #include "libc_private.h"
52 * Re-direct an existing, open (probably) file to some other file.
53 * ANSI is written such that the original file gets closed if at
54 * all possible, no matter what.
57 freopen(const char *file, const char *mode, FILE *fp)
60 int flags, isopen, oflags, sverrno, wantfd;
62 if ((flags = __sflags(mode, &oflags)) == 0) {
73 * There are actually programs that depend on being able to "freopen"
74 * descriptors that weren't originally open. Keep this from breaking.
75 * Remember whether the stream was open to begin with, and which file
76 * descriptor (if any) was associated with it. If it was attached to
77 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
78 * should work. This is unnecessary if it was not a Unix file.
80 if (fp->_flags == 0) {
81 fp->_flags = __SEOF; /* hold on to it */
85 /* flush the stream; ANSI doesn't require this. */
86 if (fp->_flags & __SWR)
88 /* if close is NULL, closing is a no-op, hence pointless */
89 isopen = fp->_close != NULL;
90 if ((wantfd = fp->_file) < 0 && isopen) {
91 (void) (*fp->_close)(fp->_cookie);
96 /* Get a new descriptor to refer to the new file. */
97 f = _open(file, oflags, DEFFILEMODE);
98 if (f < 0 && isopen) {
99 /* If out of fd's close the old one and try again. */
100 if (errno == ENFILE || errno == EMFILE) {
101 (void) (*fp->_close)(fp->_cookie);
103 f = _open(file, oflags, DEFFILEMODE);
109 * Finish closing fp. Even if the open succeeded above, we cannot
110 * keep fp->_base: it may be the wrong size. This loses the effect
111 * of any setbuffer calls, but stdio has always done this before.
114 (void) (*fp->_close)(fp->_cookie);
115 if (fp->_flags & __SMBF)
116 free((char *)fp->_bf._base);
120 fp->_bf._base = NULL;
130 if (f < 0) { /* did not get it after all */
131 fp->_flags = 0; /* set it free */
132 errno = sverrno; /* restore in case _close clobbered */
138 * If reopening something that was open before on a real file, try
139 * to maintain the descriptor. Various C library routines (perror)
140 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
142 if (wantfd >= 0 && f != wantfd) {
143 if (dup2(f, wantfd) >= 0) {
153 fp->_write = __swrite;
155 fp->_close = __sclose;