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23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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32 * @(#)freopen.c 8.1 (Berkeley) 6/4/93
33 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.21 2008/04/17 22:17:54 jhb Exp $
36 #include "namespace.h"
37 #include <sys/types.h>
44 #include "un-namespace.h"
45 #include "libc_private.h"
49 * Re-direct an existing, open (probably) file to some other file.
50 * ANSI is written such that the original file gets closed if at
51 * all possible, no matter what.
54 freopen(const char * __restrict file, const char * __restrict mode, FILE *fp)
57 int dflags, flags, isopen, oflags, sverrno, wantfd;
59 if ((flags = __sflags(mode, &oflags)) == 0) {
72 * If the filename is a NULL pointer, the caller is asking us to
73 * re-open the same file with a different mode. We allow this only
74 * if the modes are compatible.
77 /* See comment below regarding freopen() of closed files. */
78 if (fp->pub._flags == 0) {
83 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) {
90 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
91 (oflags & O_ACCMODE)) {
97 if (fp->pub._flags & __SWR)
99 if ((oflags ^ dflags) & O_APPEND) {
101 dflags |= oflags & O_APPEND;
102 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) {
110 if (oflags & O_TRUNC)
111 ftruncate(fp->pub._fileno, (off_t)0);
112 if (!(oflags & O_APPEND))
113 _sseek(fp, (fpos_t)0, SEEK_SET);
114 if (oflags & O_CLOEXEC)
115 _fcntl(fileno(fp), F_SETFD, FD_CLOEXEC);
124 * There are actually programs that depend on being able to "freopen"
125 * descriptors that weren't originally open. Keep this from breaking.
126 * Remember whether the stream was open to begin with, and which file
127 * descriptor (if any) was associated with it. If it was attached to
128 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
129 * should work. This is unnecessary if it was not a Unix file.
131 if (fp->pub._flags == 0) {
132 fp->pub._flags = __SEOF; /* hold on to it */
136 /* flush the stream; ANSI doesn't require this. */
137 if (fp->pub._flags & __SWR)
139 /* if close is NULL, closing is a no-op, hence pointless */
140 isopen = fp->_close != NULL;
141 if ((wantfd = fp->pub._fileno) < 0 && isopen) {
142 (*fp->_close)(fp->_cookie);
147 /* Get a new descriptor to refer to the new file. */
148 f = _open(file, oflags, DEFFILEMODE);
149 if (f < 0 && isopen) {
150 /* If out of fd's close the old one and try again. */
151 if (errno == ENFILE || errno == EMFILE) {
152 (*fp->_close)(fp->_cookie);
154 f = _open(file, oflags, DEFFILEMODE);
161 * Finish closing fp. Even if the open succeeded above, we cannot
162 * keep fp->_base: it may be the wrong size. This loses the effect
163 * of any setbuffer calls, but stdio has always done this before.
166 (*fp->_close)(fp->_cookie);
167 if (fp->pub._flags & __SMBF)
168 free((char *)fp->_bf._base);
172 fp->_bf._base = NULL;
174 fp->pub._lbfsize = 0;
181 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
183 if (f < 0) { /* did not get it after all */
184 fp->pub._flags = 0; /* set it free */
186 errno = sverrno; /* restore in case _close clobbered */
191 * If reopening something that was open before on a real file, try
192 * to maintain the descriptor. Various C library routines (perror)
193 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
195 if (wantfd >= 0 && f != wantfd) {
196 if (oflags & O_CLOEXEC) {
197 if (_fcntl(f, F_DUP2FD_CLOEXEC, wantfd) >= 0) {
202 if (_dup2(f, wantfd) >= 0) {
209 fp->pub._flags = flags;
213 fp->_write = __swrite;
215 fp->_close = __sclose;
217 * When opening in append mode, even though we use O_APPEND,
218 * we need to seek to the end so that ftell() gets the right
219 * answer. If the user then alters the seek pointer, or
220 * the file extends, this will fail, but there is not much
221 * we can do about this. (We could set __SAPP and check in
224 if (oflags & O_APPEND)
225 _sseek(fp, (fpos_t)0, SEEK_END);