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 #include <sys/types.h> 35 #include <sys/stat.h> 36 #include <fcntl.h> 37 #include <errno.h> 38 #include <unistd.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include "local.h" 42 43 /* 44 * Re-direct an existing, open (probably) file to some other file. 45 * ANSI is written such that the original file gets closed if at 46 * all possible, no matter what. 47 */ 48 FILE * 49 freopen(const char *file, const char *mode, FILE *fp) 50 { 51 int f; 52 int flags, isopen, oflags, sverrno, wantfd; 53 54 if ((flags = __sflags(mode, &oflags)) == 0) { 55 (void) fclose(fp); 56 return (NULL); 57 } 58 59 if (!__sdidinit) 60 __sinit(); 61 62 /* 63 * There are actually programs that depend on being able to "freopen" 64 * descriptors that weren't originally open. Keep this from breaking. 65 * Remember whether the stream was open to begin with, and which file 66 * descriptor (if any) was associated with it. If it was attached to 67 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 68 * should work. This is unnecessary if it was not a Unix file. 69 */ 70 if (fp->_flags == 0) { 71 fp->_flags = __SEOF; /* hold on to it */ 72 isopen = 0; 73 wantfd = -1; 74 } else { 75 /* flush the stream; ANSI doesn't require this. */ 76 if (fp->_flags & __SWR) 77 (void) __sflush(fp); 78 /* if close is NULL, closing is a no-op, hence pointless */ 79 isopen = fp->_close != NULL; 80 if ((wantfd = fp->_file) < 0 && isopen) { 81 (void) (*fp->_close)(fp->_cookie); 82 isopen = 0; 83 } 84 } 85 86 /* Get a new descriptor to refer to the new file. */ 87 f = open(file, oflags, DEFFILEMODE); 88 if (f < 0 && isopen) { 89 /* If out of fd's close the old one and try again. */ 90 if (errno == ENFILE || errno == EMFILE) { 91 (void) (*fp->_close)(fp->_cookie); 92 isopen = 0; 93 f = open(file, oflags, DEFFILEMODE); 94 } 95 } 96 sverrno = errno; 97 98 /* 99 * Finish closing fp. Even if the open succeeded above, we cannot 100 * keep fp->_base: it may be the wrong size. This loses the effect 101 * of any setbuffer calls, but stdio has always done this before. 102 */ 103 if (isopen && f != wantfd) 104 (void) (*fp->_close)(fp->_cookie); 105 if (fp->_flags & __SMBF) 106 free((char *)fp->_bf._base); 107 fp->_w = 0; 108 fp->_r = 0; 109 fp->_p = NULL; 110 fp->_bf._base = NULL; 111 fp->_bf._size = 0; 112 fp->_lbfsize = 0; 113 if (HASUB(fp)) 114 FREEUB(fp); 115 _UB(fp)._size = 0; 116 WCIO_FREE(fp); 117 if (HASLB(fp)) 118 FREELB(fp); 119 fp->_lb._size = 0; 120 121 if (f < 0) { /* did not get it after all */ 122 fp->_flags = 0; /* set it free */ 123 errno = sverrno; /* restore in case _close clobbered */ 124 return (NULL); 125 } 126 127 /* 128 * If reopening something that was open before on a real file, try 129 * to maintain the descriptor. Various C library routines (perror) 130 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 131 */ 132 if (wantfd >= 0 && f != wantfd) { 133 if (dup2(f, wantfd) >= 0) { 134 (void) close(f); 135 f = wantfd; 136 } 137 } 138 139 fp->_flags = flags; 140 fp->_file = f; 141 fp->_cookie = fp; 142 fp->_read = __sread; 143 fp->_write = __swrite; 144 fp->_seek = __sseek; 145 fp->_close = __sclose; 146 147 /* 148 * When opening in append mode, even though we use O_APPEND, 149 * we need to seek to the end so that ftell() gets the right 150 * answer. If the user then alters the seek pointer, or 151 * the file extends, this will fail, but there is not much 152 * we can do about this. (We could set __SAPP and check in 153 * fseek and ftell.) 154 */ 155 if (oflags & O_APPEND) 156 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); 157 return (fp); 158 } 159
