1 /* $NetBSD: freopen.c,v 1.12 2001/12/07 11:47:42 yamt 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 1.12 2001/12/07 11:47:42 yamt 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 <wchar.h> 58 #include "local.h" 59 60 /* 61 * Re-direct an existing, open (probably) file to some other file. 62 * ANSI is written such that the original file gets closed if at 63 * all possible, no matter what. 64 */ 65 FILE * 66 freopen(file, mode, fp) 67 const char *file, *mode; 68 FILE *fp; 69 { 70 int f; 71 int flags, isopen, oflags, sverrno, wantfd; 72 73 _DIAGASSERT(file != NULL); 74 _DIAGASSERT(mode != NULL); 75 _DIAGASSERT(fp != NULL); 76 77 if ((flags = __sflags(mode, &oflags)) == 0) { 78 (void) fclose(fp); 79 return (NULL); 80 } 81 82 if (!__sdidinit) 83 __sinit(); 84 85 /* 86 * There are actually programs that depend on being able to "freopen" 87 * descriptors that weren't originally open. Keep this from breaking. 88 * Remember whether the stream was open to begin with, and which file 89 * descriptor (if any) was associated with it. If it was attached to 90 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 91 * should work. This is unnecessary if it was not a Unix file. 92 */ 93 if (fp->_flags == 0) { 94 fp->_flags = __SEOF; /* hold on to it */ 95 isopen = 0; 96 wantfd = -1; 97 } else { 98 /* flush the stream; ANSI doesn't require this. */ 99 if (fp->_flags & __SWR) 100 (void) __sflush(fp); 101 /* if close is NULL, closing is a no-op, hence pointless */ 102 isopen = fp->_close != NULL; 103 if ((wantfd = fp->_file) < 0 && isopen) { 104 (void) (*fp->_close)(fp->_cookie); 105 isopen = 0; 106 } 107 } 108 109 /* Get a new descriptor to refer to the new file. */ 110 f = open(file, oflags, DEFFILEMODE); 111 if (f < 0 && isopen) { 112 /* If out of fd's close the old one and try again. */ 113 if (errno == ENFILE || errno == EMFILE) { 114 (void) (*fp->_close)(fp->_cookie); 115 isopen = 0; 116 f = open(file, oflags, DEFFILEMODE); 117 } 118 } 119 sverrno = errno; 120 121 /* 122 * Finish closing fp. Even if the open succeeded above, we cannot 123 * keep fp->_base: it may be the wrong size. This loses the effect 124 * of any setbuffer calls, but stdio has always done this before. 125 */ 126 if (isopen && f != wantfd) 127 (void) (*fp->_close)(fp->_cookie); 128 if (fp->_flags & __SMBF) 129 free((char *)fp->_bf._base); 130 fp->_w = 0; 131 fp->_r = 0; 132 fp->_p = NULL; 133 fp->_bf._base = NULL; 134 fp->_bf._size = 0; 135 fp->_lbfsize = 0; 136 if (HASUB(fp)) 137 FREEUB(fp); 138 WCIO_FREE(fp); 139 _UB(fp)._size = 0; 140 if (HASLB(fp)) 141 FREELB(fp); 142 fp->_lb._size = 0; 143 144 if (f < 0) { /* did not get it after all */ 145 fp->_flags = 0; /* set it free */ 146 errno = sverrno; /* restore in case _close clobbered */ 147 return (NULL); 148 } 149 150 if (oflags & O_NONBLOCK) { 151 struct stat st; 152 if (fstat(f, &st) == -1) { 153 sverrno = errno; 154 (void)close(f); 155 errno = sverrno; 156 return (NULL); 157 } 158 if (!S_ISREG(st.st_mode)) { 159 (void)close(f); 160 errno = EFTYPE; 161 return (NULL); 162 } 163 } 164 165 /* 166 * If reopening something that was open before on a real file, try 167 * to maintain the descriptor. Various C library routines (perror) 168 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 169 */ 170 if (wantfd >= 0 && f != wantfd) { 171 if (dup2(f, wantfd) >= 0) { 172 (void) close(f); 173 f = wantfd; 174 } 175 } 176 177 fp->_flags = flags; 178 fp->_file = f; 179 fp->_cookie = fp; 180 fp->_read = __sread; 181 fp->_write = __swrite; 182 fp->_seek = __sseek; 183 fp->_close = __sclose; 184 185 /* 186 * When reopening in append mode, even though we use O_APPEND, 187 * we need to seek to the end so that ftell() gets the right 188 * answer. If the user then alters the seek pointer, or 189 * the file extends, this will fail, but there is not much 190 * we can do about this. (We could set __SAPP and check in 191 * fseek and ftell.) 192 */ 193 if (oflags & O_APPEND) 194 (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); 195 return (fp); 196 } 197