1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * 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 /*static char *sccsid = "from: @(#)freopen.c 5.6 (Berkeley) 2/24/91";*/ 39 static char *rcsid = "$Id: freopen.c,v 1.3 1993/08/26 00:46:54 jtc Exp $"; 40 #endif /* LIBC_SCCS and not lint */ 41 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <fcntl.h> 45 #include <errno.h> 46 #include <unistd.h> 47 #include <stdio.h> 48 #include <stdlib.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 register FILE *fp; 60 { 61 register 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 if (!__sdidinit) 70 __sinit(); 71 72 /* 73 * There are actually programs that depend on being able to "freopen" 74 * descriptors that weren't originally open. Keep this from breaking. 75 * Remember whether the stream was open to begin with, and which file 76 * descriptor (if any) was associated with it. If it was attached to 77 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 78 * should work. This is unnecessary if it was not a Unix file. 79 */ 80 if (fp->_flags == 0) { 81 fp->_flags = __SEOF; /* hold on to it */ 82 isopen = 0; 83 wantfd = -1; 84 } else { 85 /* flush the stream; ANSI doesn't require this. */ 86 if (fp->_flags & __SWR) 87 (void) __sflush(fp); 88 /* if close is NULL, closing is a no-op, hence pointless */ 89 isopen = fp->_close != NULL; 90 if ((wantfd = fp->_file) < 0 && isopen) { 91 (void) (*fp->_close)(fp->_cookie); 92 isopen = 0; 93 } 94 } 95 96 /* Get a new descriptor to refer to the new file. */ 97 f = open(file, oflags, DEFFILEMODE); 98 if (f < 0 && isopen) { 99 /* If out of fd's close the old one and try again. */ 100 if (errno == ENFILE || errno == EMFILE) { 101 (void) (*fp->_close)(fp->_cookie); 102 isopen = 0; 103 f = open(file, oflags, DEFFILEMODE); 104 } 105 } 106 sverrno = errno; 107 108 /* 109 * Finish closing fp. Even if the open succeeded above, we cannot 110 * keep fp->_base: it may be the wrong size. This loses the effect 111 * of any setbuffer calls, but stdio has always done this before. 112 */ 113 if (isopen) 114 (void) (*fp->_close)(fp->_cookie); 115 if (fp->_flags & __SMBF) 116 free((char *)fp->_bf._base); 117 fp->_w = 0; 118 fp->_r = 0; 119 fp->_p = NULL; 120 fp->_bf._base = NULL; 121 fp->_bf._size = 0; 122 fp->_lbfsize = 0; 123 if (HASUB(fp)) 124 FREEUB(fp); 125 fp->_ub._size = 0; 126 if (HASLB(fp)) 127 FREELB(fp); 128 fp->_lb._size = 0; 129 130 if (f < 0) { /* did not get it after all */ 131 fp->_flags = 0; /* set it free */ 132 errno = sverrno; /* restore in case _close clobbered */ 133 return (NULL); 134 } 135 136 /* 137 * If reopening something that was open before on a real file, try 138 * to maintain the descriptor. Various C library routines (perror) 139 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 140 */ 141 if (wantfd >= 0 && f != wantfd) { 142 if (dup2(f, wantfd) >= 0) { 143 (void) close(f); 144 f = wantfd; 145 } 146 } 147 148 fp->_flags = flags; 149 fp->_file = f; 150 fp->_cookie = fp; 151 fp->_read = __sread; 152 fp->_write = __swrite; 153 fp->_seek = __sseek; 154 fp->_close = __sclose; 155 return (fp); 156 } 157