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 * @(#)freopen.c 8.1 (Berkeley) 6/4/93 37 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $ 38 * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.2 2003/06/17 04:26:46 dillon Exp $ 39 */ 40 41 #include <sys/types.h> 42 #include <sys/stat.h> 43 #include <fcntl.h> 44 #include <errno.h> 45 #include <unistd.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include "libc_private.h" 49 #include "local.h" 50 51 /* 52 * Re-direct an existing, open (probably) file to some other file. 53 * ANSI is written such that the original file gets closed if at 54 * all possible, no matter what. 55 */ 56 FILE * 57 freopen(file, mode, fp) 58 const char *file, *mode; 59 FILE *fp; 60 { 61 int f; 62 int flags, isopen, oflags, sverrno, wantfd; 63 64 if ((flags = __sflags(mode, &oflags)) == 0) { 65 (void) fclose(fp); 66 return (NULL); 67 } 68 69 FLOCKFILE(fp); 70 71 if (!__sdidinit) 72 __sinit(); 73 74 /* 75 * There are actually programs that depend on being able to "freopen" 76 * descriptors that weren't originally open. Keep this from breaking. 77 * Remember whether the stream was open to begin with, and which file 78 * descriptor (if any) was associated with it. If it was attached to 79 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 80 * should work. This is unnecessary if it was not a Unix file. 81 */ 82 if (fp->_flags == 0) { 83 fp->_flags = __SEOF; /* hold on to it */ 84 isopen = 0; 85 wantfd = -1; 86 } else { 87 /* flush the stream; ANSI doesn't require this. */ 88 if (fp->_flags & __SWR) 89 (void) __sflush(fp); 90 /* if close is NULL, closing is a no-op, hence pointless */ 91 isopen = fp->_close != NULL; 92 if ((wantfd = fp->_file) < 0 && isopen) { 93 (void) (*fp->_close)(fp->_cookie); 94 isopen = 0; 95 } 96 } 97 98 /* Get a new descriptor to refer to the new file. */ 99 f = _open(file, oflags, DEFFILEMODE); 100 if (f < 0 && isopen) { 101 /* If out of fd's close the old one and try again. */ 102 if (errno == ENFILE || errno == EMFILE) { 103 (void) (*fp->_close)(fp->_cookie); 104 isopen = 0; 105 f = _open(file, oflags, DEFFILEMODE); 106 } 107 } 108 sverrno = errno; 109 110 /* 111 * Finish closing fp. Even if the open succeeded above, we cannot 112 * keep fp->_base: it may be the wrong size. This loses the effect 113 * of any setbuffer calls, but stdio has always done this before. 114 */ 115 if (isopen) 116 (void) (*fp->_close)(fp->_cookie); 117 if (fp->_flags & __SMBF) 118 free((char *)fp->_bf._base); 119 fp->_w = 0; 120 fp->_r = 0; 121 fp->_p = NULL; 122 fp->_bf._base = NULL; 123 fp->_bf._size = 0; 124 fp->_lbfsize = 0; 125 if (HASUB(fp)) 126 FREEUB(fp); 127 fp->_ub._size = 0; 128 if (HASLB(fp)) 129 FREELB(fp); 130 fp->_lb._size = 0; 131 132 if (f < 0) { /* did not get it after all */ 133 fp->_flags = 0; /* set it free */ 134 errno = sverrno; /* restore in case _close clobbered */ 135 FUNLOCKFILE(fp); 136 return (NULL); 137 } 138 139 /* 140 * If reopening something that was open before on a real file, try 141 * to maintain the descriptor. Various C library routines (perror) 142 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 143 */ 144 if (wantfd >= 0 && f != wantfd) { 145 if (dup2(f, wantfd) >= 0) { 146 (void)_close(f); 147 f = wantfd; 148 } 149 } 150 151 fp->_flags = flags; 152 fp->_file = f; 153 fp->_cookie = fp; 154 fp->_read = __sread; 155 fp->_write = __swrite; 156 fp->_seek = __sseek; 157 fp->_close = __sclose; 158 FUNLOCKFILE(fp); 159 return (fp); 160 } 161