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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 40 #endif 41 static const char rcsid[] = 42 "$FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $"; 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include <sys/types.h> 46 #include <sys/stat.h> 47 #include <fcntl.h> 48 #include <errno.h> 49 #include <unistd.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include "libc_private.h" 53 #include "local.h" 54 55 /* 56 * Re-direct an existing, open (probably) file to some other file. 57 * ANSI is written such that the original file gets closed if at 58 * all possible, no matter what. 59 */ 60 FILE * 61 freopen(file, mode, fp) 62 const char *file, *mode; 63 FILE *fp; 64 { 65 int f; 66 int flags, isopen, oflags, sverrno, wantfd; 67 68 if ((flags = __sflags(mode, &oflags)) == 0) { 69 (void) fclose(fp); 70 return (NULL); 71 } 72 73 FLOCKFILE(fp); 74 75 if (!__sdidinit) 76 __sinit(); 77 78 /* 79 * There are actually programs that depend on being able to "freopen" 80 * descriptors that weren't originally open. Keep this from breaking. 81 * Remember whether the stream was open to begin with, and which file 82 * descriptor (if any) was associated with it. If it was attached to 83 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 84 * should work. This is unnecessary if it was not a Unix file. 85 */ 86 if (fp->_flags == 0) { 87 fp->_flags = __SEOF; /* hold on to it */ 88 isopen = 0; 89 wantfd = -1; 90 } else { 91 /* flush the stream; ANSI doesn't require this. */ 92 if (fp->_flags & __SWR) 93 (void) __sflush(fp); 94 /* if close is NULL, closing is a no-op, hence pointless */ 95 isopen = fp->_close != NULL; 96 if ((wantfd = fp->_file) < 0 && isopen) { 97 (void) (*fp->_close)(fp->_cookie); 98 isopen = 0; 99 } 100 } 101 102 /* Get a new descriptor to refer to the new file. */ 103 f = _open(file, oflags, DEFFILEMODE); 104 if (f < 0 && isopen) { 105 /* If out of fd's close the old one and try again. */ 106 if (errno == ENFILE || errno == EMFILE) { 107 (void) (*fp->_close)(fp->_cookie); 108 isopen = 0; 109 f = _open(file, oflags, DEFFILEMODE); 110 } 111 } 112 sverrno = errno; 113 114 /* 115 * Finish closing fp. Even if the open succeeded above, we cannot 116 * keep fp->_base: it may be the wrong size. This loses the effect 117 * of any setbuffer calls, but stdio has always done this before. 118 */ 119 if (isopen) 120 (void) (*fp->_close)(fp->_cookie); 121 if (fp->_flags & __SMBF) 122 free((char *)fp->_bf._base); 123 fp->_w = 0; 124 fp->_r = 0; 125 fp->_p = NULL; 126 fp->_bf._base = NULL; 127 fp->_bf._size = 0; 128 fp->_lbfsize = 0; 129 if (HASUB(fp)) 130 FREEUB(fp); 131 fp->_ub._size = 0; 132 if (HASLB(fp)) 133 FREELB(fp); 134 fp->_lb._size = 0; 135 136 if (f < 0) { /* did not get it after all */ 137 fp->_flags = 0; /* set it free */ 138 errno = sverrno; /* restore in case _close clobbered */ 139 FUNLOCKFILE(fp); 140 return (NULL); 141 } 142 143 /* 144 * If reopening something that was open before on a real file, try 145 * to maintain the descriptor. Various C library routines (perror) 146 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 147 */ 148 if (wantfd >= 0 && f != wantfd) { 149 if (dup2(f, wantfd) >= 0) { 150 (void)_close(f); 151 f = wantfd; 152 } 153 } 154 155 fp->_flags = flags; 156 fp->_file = f; 157 fp->_cookie = fp; 158 fp->_read = __sread; 159 fp->_write = __swrite; 160 fp->_seek = __sseek; 161 fp->_close = __sclose; 162 FUNLOCKFILE(fp); 163 return (fp); 164 } 165