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) 34 static char rcsid[] = "$OpenBSD: freopen.c,v 1.5 2003/06/02 20:18:37 millert Exp $"; 35 #endif /* LIBC_SCCS and not lint */ 36 37 #include <sys/types.h> 38 #include <sys/stat.h> 39 #include <fcntl.h> 40 #include <errno.h> 41 #include <unistd.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include "local.h" 45 46 /* 47 * Re-direct an existing, open (probably) file to some other file. 48 * ANSI is written such that the original file gets closed if at 49 * all possible, no matter what. 50 */ 51 FILE * 52 freopen(file, mode, fp) 53 const char *file, *mode; 54 register FILE *fp; 55 { 56 register int f; 57 int flags, isopen, oflags, sverrno, wantfd; 58 59 if ((flags = __sflags(mode, &oflags)) == 0) { 60 (void) fclose(fp); 61 return (NULL); 62 } 63 64 if (!__sdidinit) 65 __sinit(); 66 67 /* 68 * There are actually programs that depend on being able to "freopen" 69 * descriptors that weren't originally open. Keep this from breaking. 70 * Remember whether the stream was open to begin with, and which file 71 * descriptor (if any) was associated with it. If it was attached to 72 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 73 * should work. This is unnecessary if it was not a Unix file. 74 */ 75 if (fp->_flags == 0) { 76 fp->_flags = __SEOF; /* hold on to it */ 77 isopen = 0; 78 wantfd = -1; 79 } else { 80 /* flush the stream; ANSI doesn't require this. */ 81 if (fp->_flags & __SWR) 82 (void) __sflush(fp); 83 /* if close is NULL, closing is a no-op, hence pointless */ 84 isopen = fp->_close != NULL; 85 if ((wantfd = fp->_file) < 0 && isopen) { 86 (void) (*fp->_close)(fp->_cookie); 87 isopen = 0; 88 } 89 } 90 91 /* Get a new descriptor to refer to the new file. */ 92 f = open(file, oflags, DEFFILEMODE); 93 if (f < 0 && isopen) { 94 /* If out of fd's close the old one and try again. */ 95 if (errno == ENFILE || errno == EMFILE) { 96 (void) (*fp->_close)(fp->_cookie); 97 isopen = 0; 98 f = open(file, oflags, DEFFILEMODE); 99 } 100 } 101 sverrno = errno; 102 103 /* 104 * Finish closing fp. Even if the open succeeded above, we cannot 105 * keep fp->_base: it may be the wrong size. This loses the effect 106 * of any setbuffer calls, but stdio has always done this before. 107 */ 108 if (isopen && f != wantfd) 109 (void) (*fp->_close)(fp->_cookie); 110 if (fp->_flags & __SMBF) 111 free((char *)fp->_bf._base); 112 fp->_w = 0; 113 fp->_r = 0; 114 fp->_p = NULL; 115 fp->_bf._base = NULL; 116 fp->_bf._size = 0; 117 fp->_lbfsize = 0; 118 if (HASUB(fp)) 119 FREEUB(fp); 120 fp->_ub._size = 0; 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 errno = sverrno; /* restore in case _close clobbered */ 128 return (NULL); 129 } 130 131 /* 132 * If reopening something that was open before on a real file, try 133 * to maintain the descriptor. Various C library routines (perror) 134 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 135 */ 136 if (wantfd >= 0 && f != wantfd) { 137 if (dup2(f, wantfd) >= 0) { 138 (void) close(f); 139 f = wantfd; 140 } 141 } 142 143 fp->_flags = flags; 144 fp->_file = f; 145 fp->_cookie = fp; 146 fp->_read = __sread; 147 fp->_write = __swrite; 148 fp->_seek = __sseek; 149 fp->_close = __sclose; 150 151 /* 152 * When opening in append mode, even though we use O_APPEND, 153 * we need to seek to the end so that ftell() gets the right 154 * answer. If the user then alters the seek pointer, or 155 * the file extends, this will fail, but there is not much 156 * we can do about this. (We could set __SAPP and check in 157 * fseek and ftell.) 158 */ 159 if (oflags & O_APPEND) 160 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); 161 return (fp); 162 } 163