1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "namespace.h" 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <fcntl.h> 45 #include <errno.h> 46 #include <limits.h> 47 #include <unistd.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include "un-namespace.h" 51 #include "libc_private.h" 52 #include "local.h" 53 54 /* 55 * Re-direct an existing, open (probably) file to some other file. 56 * ANSI is written such that the original file gets closed if at 57 * all possible, no matter what. 58 */ 59 FILE * 60 freopen(const char * __restrict file, const char * __restrict mode, 61 FILE * __restrict fp) 62 { 63 int f; 64 int dflags, flags, isopen, oflags, sverrno, wantfd; 65 66 if ((flags = __sflags(mode, &oflags)) == 0) { 67 sverrno = errno; 68 (void) fclose(fp); 69 errno = sverrno; 70 return (NULL); 71 } 72 73 FLOCKFILE_CANCELSAFE(fp); 74 75 if (!__sdidinit) 76 __sinit(); 77 78 /* 79 * If the filename is a NULL pointer, the caller is asking us to 80 * re-open the same file with a different mode. We allow this only 81 * if the modes are compatible. 82 */ 83 if (file == NULL) { 84 /* See comment below regarding freopen() of closed files. */ 85 if (fp->_flags == 0) { 86 errno = EINVAL; 87 fp = NULL; 88 goto end; 89 } 90 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) { 91 sverrno = errno; 92 fclose(fp); 93 errno = sverrno; 94 fp = NULL; 95 goto end; 96 } 97 /* Work around incorrect O_ACCMODE. */ 98 if ((dflags & O_ACCMODE) != O_RDWR && 99 (dflags & (O_ACCMODE | O_EXEC)) != (oflags & O_ACCMODE)) { 100 fclose(fp); 101 errno = EBADF; 102 fp = NULL; 103 goto end; 104 } 105 if (fp->_flags & __SWR) 106 (void) __sflush(fp); 107 if ((oflags ^ dflags) & O_APPEND) { 108 dflags &= ~O_APPEND; 109 dflags |= oflags & O_APPEND; 110 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) { 111 sverrno = errno; 112 fclose(fp); 113 errno = sverrno; 114 fp = NULL; 115 goto end; 116 } 117 } 118 if (oflags & O_TRUNC) 119 (void) ftruncate(fp->_file, (off_t)0); 120 if (!(oflags & O_APPEND)) 121 (void) _sseek(fp, (fpos_t)0, SEEK_SET); 122 if (oflags & O_CLOEXEC) 123 (void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC); 124 f = fp->_file; 125 isopen = 0; 126 wantfd = -1; 127 goto finish; 128 } 129 130 /* 131 * There are actually programs that depend on being able to "freopen" 132 * descriptors that weren't originally open. Keep this from breaking. 133 * Remember whether the stream was open to begin with, and which file 134 * descriptor (if any) was associated with it. If it was attached to 135 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 136 * should work. This is unnecessary if it was not a Unix file. 137 */ 138 if (fp->_flags == 0) { 139 fp->_flags = __SEOF; /* hold on to it */ 140 isopen = 0; 141 wantfd = -1; 142 } else { 143 /* flush the stream; ANSI doesn't require this. */ 144 if (fp->_flags & __SWR) 145 (void) __sflush(fp); 146 /* if close is NULL, closing is a no-op, hence pointless */ 147 isopen = fp->_close != NULL; 148 if ((wantfd = fp->_file) < 0 && isopen) { 149 (void) (*fp->_close)(fp->_cookie); 150 isopen = 0; 151 } 152 } 153 154 /* Get a new descriptor to refer to the new file. */ 155 f = _open(file, oflags, DEFFILEMODE); 156 /* If out of fd's close the old one and try again. */ 157 if (f < 0 && isopen && wantfd > STDERR_FILENO && 158 (errno == ENFILE || errno == EMFILE)) { 159 (void) (*fp->_close)(fp->_cookie); 160 isopen = 0; 161 wantfd = -1; 162 f = _open(file, oflags, DEFFILEMODE); 163 } 164 sverrno = errno; 165 166 finish: 167 /* 168 * Finish closing fp. Even if the open succeeded above, we cannot 169 * keep fp->_base: it may be the wrong size. This loses the effect 170 * of any setbuffer calls, but stdio has always done this before. 171 * 172 * Leave the existing file descriptor open until dup2() is called 173 * below to avoid races where a concurrent open() in another thread 174 * could claim the existing descriptor. 175 */ 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->_orientation = 0; 191 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 192 fp->_flags2 = 0; 193 194 if (f < 0) { /* did not get it after all */ 195 if (isopen) 196 (void) (*fp->_close)(fp->_cookie); 197 fp->_flags = 0; /* set it free */ 198 errno = sverrno; /* restore in case _close clobbered */ 199 fp = NULL; 200 goto end; 201 } 202 203 /* 204 * If reopening something that was open before on a real file, try 205 * to maintain the descriptor. Various C library routines (perror) 206 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 207 */ 208 if (wantfd >= 0) { 209 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) : 210 _dup2(f, wantfd)) >= 0) { 211 (void)_close(f); 212 f = wantfd; 213 } else 214 (void)_close(fp->_file); 215 } 216 217 /* 218 * File descriptors are a full int, but _file is only a short. 219 * If we get a valid file descriptor that is greater than 220 * SHRT_MAX, then the fd will get sign-extended into an 221 * invalid file descriptor. Handle this case by failing the 222 * open. 223 */ 224 if (f > SHRT_MAX) { 225 fp->_flags = 0; /* set it free */ 226 errno = EMFILE; 227 fp = NULL; 228 goto end; 229 } 230 231 fp->_flags = flags; 232 fp->_file = f; 233 fp->_cookie = fp; 234 fp->_read = __sread; 235 fp->_write = __swrite; 236 fp->_seek = __sseek; 237 fp->_close = __sclose; 238 /* 239 * When opening in append mode, even though we use O_APPEND, 240 * we need to seek to the end so that ftell() gets the right 241 * answer. If the user then alters the seek pointer, or 242 * the file extends, this will fail, but there is not much 243 * we can do about this. (We could set __SAPP and check in 244 * fseek and ftell.) 245 */ 246 if (oflags & O_APPEND) { 247 fp->_flags2 |= __S2OAP; 248 (void) _sseek(fp, (fpos_t)0, SEEK_END); 249 } 250 end: 251 FUNLOCKFILE_CANCELSAFE(); 252 return (fp); 253 } 254