1 /* $OpenBSD: freopen.c,v 1.9 2005/08/08 08:05:36 espie Exp $ */ 2 /*- 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #define __USE_BSD 35 36 #include <sys/types.h> 37 #include <sys/stat.h> 38 #include <fcntl.h> 39 #include <errno.h> 40 #include <unistd.h> 41 #include <stdio.h> 42 #include <stdlib.h> 43 #include "local.h" 44 45 /* 46 * Re-direct an existing, open (probably) file to some other file. 47 * ANSI is written such that the original file gets closed if at 48 * all possible, no matter what. 49 */ 50 FILE * 51 freopen(const char *file, const char *mode, FILE *fp) 52 { 53 int f; 54 int flags, isopen, oflags, sverrno, wantfd; 55 56 if ((flags = __sflags(mode, &oflags)) == 0) { 57 (void) fclose(fp); 58 return (NULL); 59 } 60 61 if (!__sdidinit) 62 __sinit(); 63 64 FLOCKFILE(fp); 65 66 /* 67 * There are actually programs that depend on being able to "freopen" 68 * descriptors that weren't originally open. Keep this from breaking. 69 * Remember whether the stream was open to begin with, and which file 70 * descriptor (if any) was associated with it. If it was attached to 71 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 72 * should work. This is unnecessary if it was not a Unix file. 73 */ 74 if (fp->_flags == 0) { 75 fp->_flags = __SEOF; /* hold on to it */ 76 isopen = 0; 77 wantfd = -1; 78 } else { 79 /* flush the stream; ANSI doesn't require this. */ 80 if (fp->_flags & __SWR) 81 (void) __sflush(fp); 82 /* if close is NULL, closing is a no-op, hence pointless */ 83 isopen = fp->_close != NULL; 84 if ((wantfd = fp->_file) < 0 && isopen) { 85 (void) (*fp->_close)(fp->_cookie); 86 isopen = 0; 87 } 88 } 89 90 /* Get a new descriptor to refer to the new file. */ 91 f = open(file, oflags, DEFFILEMODE); 92 if (f < 0 && isopen) { 93 /* If out of fd's close the old one and try again. */ 94 if (errno == ENFILE || errno == EMFILE) { 95 (void) (*fp->_close)(fp->_cookie); 96 isopen = 0; 97 f = open(file, oflags, DEFFILEMODE); 98 } 99 } 100 sverrno = errno; 101 102 /* 103 * Finish closing fp. Even if the open succeeded above, we cannot 104 * keep fp->_base: it may be the wrong size. This loses the effect 105 * of any setbuffer calls, but stdio has always done this before. 106 */ 107 if (isopen && f != wantfd) 108 (void) (*fp->_close)(fp->_cookie); 109 if (fp->_flags & __SMBF) 110 free((char *)fp->_bf._base); 111 fp->_w = 0; 112 fp->_r = 0; 113 fp->_p = NULL; 114 fp->_bf._base = NULL; 115 fp->_bf._size = 0; 116 fp->_lbfsize = 0; 117 if (HASUB(fp)) 118 FREEUB(fp); 119 _UB(fp)._size = 0; 120 WCIO_FREE(fp); 121 if (HASLB(fp)) 122 FREELB(fp); 123 fp->_lb._size = 0; 124 125 if (f < 0) { /* did not get it after all */ 126 fp->_flags = 0; /* set it free */ 127 FUNLOCKFILE(fp); 128 errno = sverrno; /* restore in case _close clobbered */ 129 return (NULL); 130 } 131 132 /* 133 * If reopening something that was open before on a real file, try 134 * to maintain the descriptor. Various C library routines (perror) 135 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 136 */ 137 if (wantfd >= 0 && f != wantfd) { 138 if (dup2(f, wantfd) >= 0) { 139 (void) close(f); 140 f = wantfd; 141 } 142 } 143 144 fp->_flags = flags; 145 fp->_file = f; 146 fp->_cookie = fp; 147 fp->_read = __sread; 148 fp->_write = __swrite; 149 fp->_seek = __sseek; 150 fp->_close = __sclose; 151 152 /* 153 * When opening in append mode, even though we use O_APPEND, 154 * we need to seek to the end so that ftell() gets the right 155 * answer. If the user then alters the seek pointer, or 156 * the file extends, this will fail, but there is not much 157 * we can do about this. (We could set __SAPP and check in 158 * fseek and ftell.) 159 */ 160 if (oflags & O_APPEND) 161 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); 162 FUNLOCKFILE(fp); 163 return (fp); 164 } 165
