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 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 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 $ 34 * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.7 2005/11/20 11:07:30 swildner Exp $ 35 */ 36 37 #include "namespace.h" 38 #include <sys/types.h> 39 #include <sys/stat.h> 40 #include <fcntl.h> 41 #include <errno.h> 42 #include <unistd.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include "un-namespace.h" 46 #include "libc_private.h" 47 #include "local.h" 48 #include "priv_stdio.h" 49 50 /* 51 * Re-direct an existing, open (probably) file to some other file. 52 * ANSI is written such that the original file gets closed if at 53 * all possible, no matter what. 54 */ 55 FILE * 56 freopen(const char * __restrict file, const char * __restrict mode, FILE *fp) 57 { 58 int f; 59 int dflags, flags, isopen, oflags, sverrno, wantfd; 60 61 if ((flags = __sflags(mode, &oflags)) == 0) { 62 sverrno = errno; 63 fclose(fp); 64 errno = sverrno; 65 return (NULL); 66 } 67 68 FLOCKFILE(fp); 69 70 if (!__sdidinit) 71 __sinit(); 72 73 /* 74 * If the filename is a NULL pointer, the caller is asking us to 75 * re-open the same file with a different mode. We allow this only 76 * if the modes are compatible. 77 */ 78 if (file == NULL) { 79 /* See comment below regarding freopen() of closed files. */ 80 if (fp->pub._flags == 0) { 81 FUNLOCKFILE(fp); 82 errno = EINVAL; 83 return (NULL); 84 } 85 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) { 86 sverrno = errno; 87 fclose(fp); 88 FUNLOCKFILE(fp); 89 errno = sverrno; 90 return (NULL); 91 } 92 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) != 93 (oflags & O_ACCMODE)) { 94 fclose(fp); 95 FUNLOCKFILE(fp); 96 errno = EINVAL; 97 return (NULL); 98 } 99 if (fp->pub._flags & __SWR) 100 __sflush(fp); 101 if ((oflags ^ dflags) & O_APPEND) { 102 dflags &= ~O_APPEND; 103 dflags |= oflags & O_APPEND; 104 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) { 105 sverrno = errno; 106 fclose(fp); 107 FUNLOCKFILE(fp); 108 errno = sverrno; 109 return (NULL); 110 } 111 } 112 if (oflags & O_TRUNC) 113 ftruncate(fp->pub._fileno, (off_t)0); 114 if (!(oflags & O_APPEND)) 115 _sseek(fp, (fpos_t)0, SEEK_SET); 116 f = fp->pub._fileno; 117 isopen = 0; 118 wantfd = -1; 119 goto finish; 120 } 121 122 /* 123 * There are actually programs that depend on being able to "freopen" 124 * descriptors that weren't originally open. Keep this from breaking. 125 * Remember whether the stream was open to begin with, and which file 126 * descriptor (if any) was associated with it. If it was attached to 127 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 128 * should work. This is unnecessary if it was not a Unix file. 129 */ 130 if (fp->pub._flags == 0) { 131 fp->pub._flags = __SEOF; /* hold on to it */ 132 isopen = 0; 133 wantfd = -1; 134 } else { 135 /* flush the stream; ANSI doesn't require this. */ 136 if (fp->pub._flags & __SWR) 137 __sflush(fp); 138 /* if close is NULL, closing is a no-op, hence pointless */ 139 isopen = fp->_close != NULL; 140 if ((wantfd = fp->pub._fileno) < 0 && isopen) { 141 (*fp->_close)(fp->_cookie); 142 isopen = 0; 143 } 144 } 145 146 /* Get a new descriptor to refer to the new file. */ 147 f = _open(file, oflags, DEFFILEMODE); 148 if (f < 0 && isopen) { 149 /* If out of fd's close the old one and try again. */ 150 if (errno == ENFILE || errno == EMFILE) { 151 (*fp->_close)(fp->_cookie); 152 isopen = 0; 153 f = _open(file, oflags, DEFFILEMODE); 154 } 155 } 156 sverrno = errno; 157 158 finish: 159 /* 160 * Finish closing fp. Even if the open succeeded above, we cannot 161 * keep fp->_base: it may be the wrong size. This loses the effect 162 * of any setbuffer calls, but stdio has always done this before. 163 */ 164 if (isopen) 165 (*fp->_close)(fp->_cookie); 166 if (fp->pub._flags & __SMBF) 167 free((char *)fp->_bf._base); 168 fp->pub._w = 0; 169 fp->pub._r = 0; 170 fp->pub._p = NULL; 171 fp->_bf._base = NULL; 172 fp->_bf._size = 0; 173 fp->pub._lbfsize = 0; 174 if (HASUB(fp)) 175 FREEUB(fp); 176 fp->_ub._size = 0; 177 if (HASLB(fp)) 178 FREELB(fp); 179 fp->_lb._size = 0; 180 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data)); 181 182 if (f < 0) { /* did not get it after all */ 183 fp->pub._flags = 0; /* set it free */ 184 FUNLOCKFILE(fp); 185 errno = sverrno; /* restore in case _close clobbered */ 186 return (NULL); 187 } 188 189 /* 190 * If reopening something that was open before on a real file, try 191 * to maintain the descriptor. Various C library routines (perror) 192 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 193 */ 194 if (wantfd >= 0 && f != wantfd) { 195 if (_dup2(f, wantfd) >= 0) { 196 _close(f); 197 f = wantfd; 198 } 199 } 200 201 fp->pub._flags = flags; 202 fp->pub._fileno = f; 203 fp->_cookie = fp; 204 fp->_read = __sread; 205 fp->_write = __swrite; 206 fp->_seek = __sseek; 207 fp->_close = __sclose; 208 /* 209 * When opening in append mode, even though we use O_APPEND, 210 * we need to seek to the end so that ftell() gets the right 211 * answer. If the user then alters the seek pointer, or 212 * the file extends, this will fail, but there is not much 213 * we can do about this. (We could set __SAPP and check in 214 * fseek and ftell.) 215 */ 216 if (oflags & O_APPEND) 217 _sseek(fp, (fpos_t)0, SEEK_END); 218 FUNLOCKFILE(fp); 219 return (fp); 220 } 221