freopen.c revision 249808
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 33#if defined(LIBC_SCCS) && !defined(lint) 34static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 35#endif /* LIBC_SCCS and not lint */ 36#include <sys/cdefs.h> 37__FBSDID("$FreeBSD: head/lib/libc/stdio/freopen.c 249808 2013-04-23 13:33:13Z emaste $"); 38 39#include "namespace.h" 40#include <sys/types.h> 41#include <sys/stat.h> 42#include <fcntl.h> 43#include <errno.h> 44#include <limits.h> 45#include <unistd.h> 46#include <stdio.h> 47#include <stdlib.h> 48#include "un-namespace.h" 49#include "libc_private.h" 50#include "local.h" 51 52/* 53 * Re-direct an existing, open (probably) file to some other file. 54 * ANSI is written such that the original file gets closed if at 55 * all possible, no matter what. 56 */ 57FILE * 58freopen(file, mode, fp) 59 const char * __restrict file; 60 const char * __restrict mode; 61 FILE *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(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 FUNLOCKFILE(fp); 87 errno = EINVAL; 88 return (NULL); 89 } 90 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) { 91 sverrno = errno; 92 fclose(fp); 93 FUNLOCKFILE(fp); 94 errno = sverrno; 95 return (NULL); 96 } 97 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) != 98 (oflags & O_ACCMODE)) { 99 fclose(fp); 100 FUNLOCKFILE(fp); 101 errno = EINVAL; 102 return (NULL); 103 } 104 if (fp->_flags & __SWR) 105 (void) __sflush(fp); 106 if ((oflags ^ dflags) & O_APPEND) { 107 dflags &= ~O_APPEND; 108 dflags |= oflags & O_APPEND; 109 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) { 110 sverrno = errno; 111 fclose(fp); 112 FUNLOCKFILE(fp); 113 errno = sverrno; 114 return (NULL); 115 } 116 } 117 if (oflags & O_TRUNC) 118 (void) ftruncate(fp->_file, (off_t)0); 119 if (!(oflags & O_APPEND)) 120 (void) _sseek(fp, (fpos_t)0, SEEK_SET); 121 if (oflags & O_CLOEXEC) 122 (void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC); 123 f = fp->_file; 124 isopen = 0; 125 wantfd = -1; 126 goto finish; 127 } 128 129 /* 130 * There are actually programs that depend on being able to "freopen" 131 * descriptors that weren't originally open. Keep this from breaking. 132 * Remember whether the stream was open to begin with, and which file 133 * descriptor (if any) was associated with it. If it was attached to 134 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 135 * should work. This is unnecessary if it was not a Unix file. 136 */ 137 if (fp->_flags == 0) { 138 fp->_flags = __SEOF; /* hold on to it */ 139 isopen = 0; 140 wantfd = -1; 141 } else { 142 /* flush the stream; ANSI doesn't require this. */ 143 if (fp->_flags & __SWR) 144 (void) __sflush(fp); 145 /* if close is NULL, closing is a no-op, hence pointless */ 146 isopen = fp->_close != NULL; 147 if ((wantfd = fp->_file) < 0 && isopen) { 148 (void) (*fp->_close)(fp->_cookie); 149 isopen = 0; 150 } 151 } 152 153 /* Get a new descriptor to refer to the new file. */ 154 f = _open(file, oflags, DEFFILEMODE); 155 sverrno = errno; 156 157finish: 158 /* 159 * Finish closing fp. Even if the open succeeded above, we cannot 160 * keep fp->_base: it may be the wrong size. This loses the effect 161 * of any setbuffer calls, but stdio has always done this before. 162 * 163 * Leave the existing file descriptor open until dup2() is called 164 * below to avoid races where a concurrent open() in another thread 165 * could claim the existing descriptor. 166 */ 167 if (fp->_flags & __SMBF) 168 free((char *)fp->_bf._base); 169 fp->_w = 0; 170 fp->_r = 0; 171 fp->_p = NULL; 172 fp->_bf._base = NULL; 173 fp->_bf._size = 0; 174 fp->_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 fp->_orientation = 0; 182 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 183 184 if (f < 0) { /* did not get it after all */ 185 if (isopen) 186 (void) (*fp->_close)(fp->_cookie); 187 fp->_flags = 0; /* set it free */ 188 FUNLOCKFILE(fp); 189 errno = sverrno; /* restore in case _close clobbered */ 190 return (NULL); 191 } 192 193 /* 194 * If reopening something that was open before on a real file, try 195 * to maintain the descriptor. Various C library routines (perror) 196 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 197 */ 198 if (wantfd >= 0) { 199 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) : 200 _dup2(f, wantfd)) >= 0) { 201 (void)_close(f); 202 f = wantfd; 203 } else 204 (void)_close(fp->_file); 205 } 206 207 /* 208 * File descriptors are a full int, but _file is only a short. 209 * If we get a valid file descriptor that is greater than 210 * SHRT_MAX, then the fd will get sign-extended into an 211 * invalid file descriptor. Handle this case by failing the 212 * open. 213 */ 214 if (f > SHRT_MAX) { 215 fp->_flags = 0; /* set it free */ 216 FUNLOCKFILE(fp); 217 errno = EMFILE; 218 return (NULL); 219 } 220 221 fp->_flags = flags; 222 fp->_file = f; 223 fp->_cookie = fp; 224 fp->_read = __sread; 225 fp->_write = __swrite; 226 fp->_seek = __sseek; 227 fp->_close = __sclose; 228 /* 229 * When opening in append mode, even though we use O_APPEND, 230 * we need to seek to the end so that ftell() gets the right 231 * answer. If the user then alters the seek pointer, or 232 * the file extends, this will fail, but there is not much 233 * we can do about this. (We could set __SAPP and check in 234 * fseek and ftell.) 235 */ 236 if (oflags & O_APPEND) 237 (void) _sseek(fp, (fpos_t)0, SEEK_END); 238 FUNLOCKFILE(fp); 239 return (fp); 240} 241