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 * @(#)freopen.c 8.1 (Berkeley) 6/4/93 37 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $ 38 * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.4 2004/06/08 00:45:00 hmp Exp $ 39 */ 40 41 #include <sys/types.h> 42 #include <sys/stat.h> 43 #include <fcntl.h> 44 #include <errno.h> 45 #include <unistd.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include "libc_private.h" 49 #include "local.h" 50 51 /* 52 * Re-direct an existing, open (probably) file to some other file. 53 * ANSI is written such that the original file gets closed if at 54 * all possible, no matter what. 55 */ 56 FILE * 57 freopen(const char *file, const char *mode, FILE *fp) 58 { 59 int f; 60 int dflags, flags, isopen, oflags, sverrno, wantfd; 61 62 if ((flags = __sflags(mode, &oflags)) == 0) { 63 (void) fclose(fp); 64 return (NULL); 65 } 66 67 FLOCKFILE(fp); 68 69 if (!__sdidinit) 70 __sinit(); 71 72 sverrno = 0; 73 74 /* 75 * If the filename is a NULL pointer, the caller is asking us to 76 * re-open the same file with a different mode. We allow this only 77 * if the modes are compatible. 78 */ 79 if (file == NULL) { 80 /* See comment below regarding freopen() of closed files. */ 81 if (fp->_flags == 0) { 82 FUNLOCKFILE(fp); 83 errno = EINVAL; 84 return (NULL); 85 } 86 if ((dflags = fcntl(fp->_file, F_GETFL)) < 0) { 87 sverrno = errno; 88 fclose(fp); 89 FUNLOCKFILE(fp); 90 errno = sverrno; 91 return (NULL); 92 } 93 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) != 94 (oflags & O_ACCMODE)) { 95 fclose(fp); 96 FUNLOCKFILE(fp); 97 errno = EINVAL; 98 return (NULL); 99 } 100 if ((oflags ^ dflags) & O_APPEND) { 101 dflags &= ~O_APPEND; 102 dflags |= oflags & O_APPEND; 103 if (fcntl(fp->_file, F_SETFL, dflags) < 0) { 104 sverrno = errno; 105 fclose(fp); 106 FUNLOCKFILE(fp); 107 errno = sverrno; 108 return (NULL); 109 } 110 } 111 if (oflags & O_TRUNC) 112 ftruncate(fp->_file, 0); 113 if (fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET) < 0 && 114 errno != ESPIPE) { 115 sverrno = errno; 116 fclose(fp); 117 FUNLOCKFILE(fp); 118 errno = sverrno; 119 return (NULL); 120 } 121 f = fp->_file; 122 isopen = 0; 123 wantfd = -1; 124 goto finish; 125 } 126 127 /* 128 * There are actually programs that depend on being able to "freopen" 129 * descriptors that weren't originally open. Keep this from breaking. 130 * Remember whether the stream was open to begin with, and which file 131 * descriptor (if any) was associated with it. If it was attached to 132 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 133 * should work. This is unnecessary if it was not a Unix file. 134 */ 135 if (fp->_flags == 0) { 136 fp->_flags = __SEOF; /* hold on to it */ 137 isopen = 0; 138 wantfd = -1; 139 } else { 140 /* flush the stream; ANSI doesn't require this. */ 141 if (fp->_flags & __SWR) 142 (void) __sflush(fp); 143 /* if close is NULL, closing is a no-op, hence pointless */ 144 isopen = fp->_close != NULL; 145 if ((wantfd = fp->_file) < 0 && isopen) { 146 (void) (*fp->_close)(fp->_cookie); 147 isopen = 0; 148 } 149 } 150 151 /* Get a new descriptor to refer to the new file. */ 152 f = _open(file, oflags, DEFFILEMODE); 153 if (f < 0 && isopen) { 154 /* If out of fd's close the old one and try again. */ 155 if (errno == ENFILE || errno == EMFILE) { 156 (void) (*fp->_close)(fp->_cookie); 157 isopen = 0; 158 f = _open(file, oflags, DEFFILEMODE); 159 } 160 } 161 sverrno = errno; 162 163 finish: 164 /* 165 * Finish closing fp. Even if the open succeeded above, we cannot 166 * keep fp->_base: it may be the wrong size. This loses the effect 167 * of any setbuffer calls, but stdio has always done this before. 168 */ 169 if (isopen) 170 (void) (*fp->_close)(fp->_cookie); 171 if (fp->_flags & __SMBF) 172 free((char *)fp->_bf._base); 173 fp->_w = 0; 174 fp->_r = 0; 175 fp->_p = NULL; 176 fp->_bf._base = NULL; 177 fp->_bf._size = 0; 178 fp->_lbfsize = 0; 179 if (HASUB(fp)) 180 FREEUB(fp); 181 fp->_ub._size = 0; 182 if (HASLB(fp)) 183 FREELB(fp); 184 fp->_lb._size = 0; 185 186 if (f < 0) { /* did not get it after all */ 187 fp->_flags = 0; /* set it free */ 188 errno = sverrno; /* restore in case _close clobbered */ 189 FUNLOCKFILE(fp); 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 && f != wantfd) { 199 if (dup2(f, wantfd) >= 0) { 200 (void)_close(f); 201 f = wantfd; 202 } 203 } 204 205 fp->_flags = flags; 206 fp->_file = f; 207 fp->_cookie = fp; 208 fp->_read = __sread; 209 fp->_write = __swrite; 210 fp->_seek = __sseek; 211 fp->_close = __sclose; 212 FUNLOCKFILE(fp); 213 return (fp); 214 } 215