freopen.c revision 129583
1/*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#if defined(LIBC_SCCS) && !defined(lint) 38static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 39#endif /* LIBC_SCCS and not lint */ 40#include <sys/cdefs.h> 41__FBSDID("$FreeBSD: head/lib/libc/stdio/freopen.c 129583 2004-05-22 15:19:41Z tjr $"); 42 43#include "namespace.h" 44#include <sys/types.h> 45#include <sys/stat.h> 46#include <fcntl.h> 47#include <errno.h> 48#include <unistd.h> 49#include <stdio.h> 50#include <stdlib.h> 51#include "un-namespace.h" 52#include "libc_private.h" 53#include "local.h" 54 55/* 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. 59 */ 60FILE * 61freopen(file, mode, fp) 62 const char * __restrict file; 63 const char * __restrict mode; 64 FILE *fp; 65{ 66 int f; 67 int dflags, flags, isopen, oflags, sverrno, wantfd; 68 69 if ((flags = __sflags(mode, &oflags)) == 0) { 70 (void) fclose(fp); 71 return (NULL); 72 } 73 74 FLOCKFILE(fp); 75 76 if (!__sdidinit) 77 __sinit(); 78 79 /* 80 * If the filename is a NULL pointer, the caller is asking us to 81 * re-open the same file with a different mode. We allow this only 82 * if the modes are compatible. 83 */ 84 if (file == NULL) { 85 /* See comment below regarding freopen() of closed files. */ 86 if (fp->_flags == 0) { 87 FUNLOCKFILE(fp); 88 errno = EINVAL; 89 return (NULL); 90 } 91 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) { 92 sverrno = errno; 93 fclose(fp); 94 FUNLOCKFILE(fp); 95 errno = sverrno; 96 return (NULL); 97 } 98 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) != 99 (oflags & O_ACCMODE)) { 100 fclose(fp); 101 FUNLOCKFILE(fp); 102 errno = EINVAL; 103 return (NULL); 104 } 105 if ((oflags ^ dflags) & O_APPEND) { 106 dflags &= ~O_APPEND; 107 dflags |= oflags & O_APPEND; 108 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) { 109 sverrno = errno; 110 fclose(fp); 111 FUNLOCKFILE(fp); 112 errno = sverrno; 113 return (NULL); 114 } 115 } 116 if (oflags & O_TRUNC) 117 ftruncate(fp->_file, 0); 118 if (_fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET, 119 0) < 0 && errno != ESPIPE) { 120 sverrno = errno; 121 fclose(fp); 122 FUNLOCKFILE(fp); 123 errno = sverrno; 124 return (NULL); 125 } 126 f = fp->_file; 127 isopen = 0; 128 wantfd = -1; 129 goto finish; 130 } 131 132 /* 133 * There are actually programs that depend on being able to "freopen" 134 * descriptors that weren't originally open. Keep this from breaking. 135 * Remember whether the stream was open to begin with, and which file 136 * descriptor (if any) was associated with it. If it was attached to 137 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 138 * should work. This is unnecessary if it was not a Unix file. 139 */ 140 if (fp->_flags == 0) { 141 fp->_flags = __SEOF; /* hold on to it */ 142 isopen = 0; 143 wantfd = -1; 144 } else { 145 /* flush the stream; ANSI doesn't require this. */ 146 if (fp->_flags & __SWR) 147 (void) __sflush(fp); 148 /* if close is NULL, closing is a no-op, hence pointless */ 149 isopen = fp->_close != NULL; 150 if ((wantfd = fp->_file) < 0 && isopen) { 151 (void) (*fp->_close)(fp->_cookie); 152 isopen = 0; 153 } 154 } 155 156 /* Get a new descriptor to refer to the new file. */ 157 f = _open(file, oflags, DEFFILEMODE); 158 if (f < 0 && isopen) { 159 /* If out of fd's close the old one and try again. */ 160 if (errno == ENFILE || errno == EMFILE) { 161 (void) (*fp->_close)(fp->_cookie); 162 isopen = 0; 163 f = _open(file, oflags, DEFFILEMODE); 164 } 165 } 166 sverrno = errno; 167 168finish: 169 /* 170 * Finish closing fp. Even if the open succeeded above, we cannot 171 * keep fp->_base: it may be the wrong size. This loses the effect 172 * of any setbuffer calls, but stdio has always done this before. 173 */ 174 if (isopen) 175 (void) (*fp->_close)(fp->_cookie); 176 if (fp->_flags & __SMBF) 177 free((char *)fp->_bf._base); 178 fp->_w = 0; 179 fp->_r = 0; 180 fp->_p = NULL; 181 fp->_bf._base = NULL; 182 fp->_bf._size = 0; 183 fp->_lbfsize = 0; 184 if (HASUB(fp)) 185 FREEUB(fp); 186 fp->_ub._size = 0; 187 if (HASLB(fp)) 188 FREELB(fp); 189 fp->_lb._size = 0; 190 fp->_extra->orientation = 0; 191 memset(&fp->_extra->mbstate, 0, sizeof(mbstate_t)); 192 193 if (f < 0) { /* did not get it after all */ 194 fp->_flags = 0; /* set it free */ 195 errno = sverrno; /* restore in case _close clobbered */ 196 FUNLOCKFILE(fp); 197 return (NULL); 198 } 199 200 /* 201 * If reopening something that was open before on a real file, try 202 * to maintain the descriptor. Various C library routines (perror) 203 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 204 */ 205 if (wantfd >= 0 && f != wantfd) { 206 if (_dup2(f, wantfd) >= 0) { 207 (void)_close(f); 208 f = wantfd; 209 } 210 } 211 212 fp->_flags = flags; 213 fp->_file = f; 214 fp->_cookie = fp; 215 fp->_read = __sread; 216 fp->_write = __swrite; 217 fp->_seek = __sseek; 218 fp->_close = __sclose; 219 FUNLOCKFILE(fp); 220 return (fp); 221} 222