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. 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 */ 35 36 #include "namespace.h" 37 #include <sys/types.h> 38 #include <sys/stat.h> 39 #include <fcntl.h> 40 #include <errno.h> 41 #include <unistd.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include "un-namespace.h" 45 #include "libc_private.h" 46 #include "local.h" 47 48 /* 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. 52 */ 53 FILE * 54 freopen(const char * __restrict file, const char * __restrict mode, FILE *fp) 55 { 56 int f; 57 int dflags, flags, isopen, oflags, sverrno, wantfd; 58 59 if ((flags = __sflags(mode, &oflags)) == 0) { 60 sverrno = errno; 61 fclose(fp); 62 errno = sverrno; 63 return (NULL); 64 } 65 66 FLOCKFILE(fp); 67 68 if (!__sdidinit) 69 __sinit(); 70 71 /* 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. 75 */ 76 if (file == NULL) { 77 /* See comment below regarding freopen() of closed files. */ 78 if (fp->pub._flags == 0) { 79 FUNLOCKFILE(fp); 80 errno = EINVAL; 81 return (NULL); 82 } 83 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) { 84 sverrno = errno; 85 fclose(fp); 86 FUNLOCKFILE(fp); 87 errno = sverrno; 88 return (NULL); 89 } 90 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) != 91 (oflags & O_ACCMODE)) { 92 fclose(fp); 93 FUNLOCKFILE(fp); 94 errno = EINVAL; 95 return (NULL); 96 } 97 if (fp->pub._flags & __SWR) 98 __sflush(fp); 99 if ((oflags ^ dflags) & O_APPEND) { 100 dflags &= ~O_APPEND; 101 dflags |= oflags & O_APPEND; 102 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) { 103 sverrno = errno; 104 fclose(fp); 105 FUNLOCKFILE(fp); 106 errno = sverrno; 107 return (NULL); 108 } 109 } 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); 116 117 f = fp->pub._fileno; 118 isopen = 0; 119 wantfd = -1; 120 goto finish; 121 } 122 123 /* 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. 130 */ 131 if (fp->pub._flags == 0) { 132 fp->pub._flags = __SEOF; /* hold on to it */ 133 isopen = 0; 134 wantfd = -1; 135 } else { 136 /* flush the stream; ANSI doesn't require this. */ 137 if (fp->pub._flags & __SWR) 138 __sflush(fp); 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); 143 isopen = 0; 144 } 145 } 146 147 /* 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); 153 isopen = 0; 154 f = _open(file, oflags, DEFFILEMODE); 155 } 156 } 157 sverrno = errno; 158 159 finish: 160 /* 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. 164 */ 165 if (isopen) 166 (*fp->_close)(fp->_cookie); 167 if (fp->pub._flags & __SMBF) 168 free((char *)fp->_bf._base); 169 fp->pub._w = 0; 170 fp->pub._r = 0; 171 fp->pub._p = NULL; 172 fp->_bf._base = NULL; 173 fp->_bf._size = 0; 174 fp->pub._lbfsize = 0; 175 if (HASUB(fp)) 176 FREEUB(fp); 177 fp->_ub._size = 0; 178 if (HASLB(fp)) 179 FREELB(fp); 180 fp->_lb._size = 0; 181 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data)); 182 183 if (f < 0) { /* did not get it after all */ 184 fp->pub._flags = 0; /* set it free */ 185 FUNLOCKFILE(fp); 186 errno = sverrno; /* restore in case _close clobbered */ 187 return (NULL); 188 } 189 190 /* 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. 194 */ 195 if (wantfd >= 0 && f != wantfd) { 196 if (oflags & O_CLOEXEC) { 197 if (_fcntl(f, F_DUP2FD_CLOEXEC, wantfd) >= 0) { 198 _close(f); 199 f = wantfd; 200 } 201 } else { 202 if (_dup2(f, wantfd) >= 0) { 203 _close(f); 204 f = wantfd; 205 } 206 } 207 } 208 209 fp->pub._flags = flags; 210 fp->pub._fileno = f; 211 fp->_cookie = fp; 212 fp->_read = __sread; 213 fp->_write = __swrite; 214 fp->_seek = __sseek; 215 fp->_close = __sclose; 216 /* 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 222 * fseek and ftell.) 223 */ 224 if (oflags & O_APPEND) 225 _sseek(fp, (fpos_t)0, SEEK_END); 226 FUNLOCKFILE(fp); 227 return (fp); 228 } 229