1 /* $NetBSD: freopen.c,v 1.10 1999/09/20 04:39:28 lukem Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 43 #else 44 __RCSID("$NetBSD: freopen.c,v 1.10 1999/09/20 04:39:28 lukem Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 #include <sys/types.h> 49 #include <sys/stat.h> 50 51 #include <assert.h> 52 #include <errno.h> 53 #include <fcntl.h> 54 #include <unistd.h> 55 #include <stdio.h> 56 #include <stdlib.h> 57 #include "local.h" 58 59 /* 60 * Re-direct an existing, open (probably) file to some other file. 61 * ANSI is written such that the original file gets closed if at 62 * all possible, no matter what. 63 */ 64 FILE * 65 freopen(file, mode, fp) 66 const char *file, *mode; 67 FILE *fp; 68 { 69 int f; 70 int flags, isopen, oflags, sverrno, wantfd; 71 72 _DIAGASSERT(file != NULL); 73 _DIAGASSERT(mode != NULL); 74 _DIAGASSERT(fp != NULL); 75 76 if ((flags = __sflags(mode, &oflags)) == 0) { 77 (void) fclose(fp); 78 return (NULL); 79 } 80 81 if (!__sdidinit) 82 __sinit(); 83 84 /* 85 * There are actually programs that depend on being able to "freopen" 86 * descriptors that weren't originally open. Keep this from breaking. 87 * Remember whether the stream was open to begin with, and which file 88 * descriptor (if any) was associated with it. If it was attached to 89 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 90 * should work. This is unnecessary if it was not a Unix file. 91 */ 92 if (fp->_flags == 0) { 93 fp->_flags = __SEOF; /* hold on to it */ 94 isopen = 0; 95 wantfd = -1; 96 } else { 97 /* flush the stream; ANSI doesn't require this. */ 98 if (fp->_flags & __SWR) 99 (void) __sflush(fp); 100 /* if close is NULL, closing is a no-op, hence pointless */ 101 isopen = fp->_close != NULL; 102 if ((wantfd = fp->_file) < 0 && isopen) { 103 (void) (*fp->_close)(fp->_cookie); 104 isopen = 0; 105 } 106 } 107 108 /* Get a new descriptor to refer to the new file. */ 109 f = open(file, oflags, DEFFILEMODE); 110 if (f < 0 && isopen) { 111 /* If out of fd's close the old one and try again. */ 112 if (errno == ENFILE || errno == EMFILE) { 113 (void) (*fp->_close)(fp->_cookie); 114 isopen = 0; 115 f = open(file, oflags, DEFFILEMODE); 116 } 117 } 118 sverrno = errno; 119 120 /* 121 * Finish closing fp. Even if the open succeeded above, we cannot 122 * keep fp->_base: it may be the wrong size. This loses the effect 123 * of any setbuffer calls, but stdio has always done this before. 124 */ 125 if (isopen && f != wantfd) 126 (void) (*fp->_close)(fp->_cookie); 127 if (fp->_flags & __SMBF) 128 free((char *)fp->_bf._base); 129 fp->_w = 0; 130 fp->_r = 0; 131 fp->_p = NULL; 132 fp->_bf._base = NULL; 133 fp->_bf._size = 0; 134 fp->_lbfsize = 0; 135 if (HASUB(fp)) 136 FREEUB(fp); 137 fp->_ub._size = 0; 138 if (HASLB(fp)) 139 FREELB(fp); 140 fp->_lb._size = 0; 141 142 if (f < 0) { /* did not get it after all */ 143 fp->_flags = 0; /* set it free */ 144 errno = sverrno; /* restore in case _close clobbered */ 145 return (NULL); 146 } 147 148 /* 149 * If reopening something that was open before on a real file, try 150 * to maintain the descriptor. Various C library routines (perror) 151 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 152 */ 153 if (wantfd >= 0 && f != wantfd) { 154 if (dup2(f, wantfd) >= 0) { 155 (void) close(f); 156 f = wantfd; 157 } 158 } 159 160 fp->_flags = flags; 161 fp->_file = f; 162 fp->_cookie = fp; 163 fp->_read = __sread; 164 fp->_write = __swrite; 165 fp->_seek = __sseek; 166 fp->_close = __sclose; 167 168 /* 169 * When reopening in append mode, even though we use O_APPEND, 170 * we need to seek to the end so that ftell() gets the right 171 * answer. If the user then alters the seek pointer, or 172 * the file extends, this will fail, but there is not much 173 * we can do about this. (We could set __SAPP and check in 174 * fseek and ftell.) 175 */ 176 if (oflags & O_APPEND) 177 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); 178 return (fp); 179 } 180