freopen.c (5040B)
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 static char rcsid[] = "$OpenBSD: freopen.c,v 1.3 1996/08/19 08:32:45 tholo Exp $"; 39 #endif /* LIBC_SCCS and not lint */ 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 "local.h" 49 50 /* 51 * Re-direct an existing, open (probably) file to some other file. 52 * ANSI is written such that the original file gets closed if at 53 * all possible, no matter what. 54 */ 55 FILE * 56 freopen(file, mode, fp) 57 const char *file, *mode; 58 register FILE *fp; 59 { 60 register int f; 61 int flags, isopen, oflags, sverrno, wantfd; 62 63 if ((flags = __sflags(mode, &oflags)) == 0) { 64 (void) fclose(fp); 65 return (NULL); 66 } 67 68 if (!__sdidinit) 69 __sinit(); 70 71 /* 72 * There are actually programs that depend on being able to "freopen" 73 * descriptors that weren't originally open. Keep this from breaking. 74 * Remember whether the stream was open to begin with, and which file 75 * descriptor (if any) was associated with it. If it was attached to 76 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 77 * should work. This is unnecessary if it was not a Unix file. 78 */ 79 if (fp->_flags == 0) { 80 fp->_flags = __SEOF; /* hold on to it */ 81 isopen = 0; 82 wantfd = -1; 83 } else { 84 /* flush the stream; ANSI doesn't require this. */ 85 if (fp->_flags & __SWR) 86 (void) __sflush(fp); 87 /* if close is NULL, closing is a no-op, hence pointless */ 88 isopen = fp->_close != NULL; 89 if ((wantfd = fp->_file) < 0 && isopen) { 90 (void) (*fp->_close)(fp->_cookie); 91 isopen = 0; 92 } 93 } 94 95 /* Get a new descriptor to refer to the new file. */ 96 f = open(file, oflags, DEFFILEMODE); 97 if (f < 0 && isopen) { 98 /* If out of fd's close the old one and try again. */ 99 if (errno == ENFILE || errno == EMFILE) { 100 (void) (*fp->_close)(fp->_cookie); 101 isopen = 0; 102 f = open(file, oflags, DEFFILEMODE); 103 } 104 } 105 sverrno = errno; 106 107 /* 108 * Finish closing fp. Even if the open succeeded above, we cannot 109 * keep fp->_base: it may be the wrong size. This loses the effect 110 * of any setbuffer calls, but stdio has always done this before. 111 */ 112 if (isopen && f != wantfd) 113 (void) (*fp->_close)(fp->_cookie); 114 if (fp->_flags & __SMBF) 115 free((char *)fp->_bf._base); 116 fp->_w = 0; 117 fp->_r = 0; 118 fp->_p = NULL; 119 fp->_bf._base = NULL; 120 fp->_bf._size = 0; 121 fp->_lbfsize = 0; 122 if (HASUB(fp)) 123 FREEUB(fp); 124 fp->_ub._size = 0; 125 if (HASLB(fp)) 126 FREELB(fp); 127 fp->_lb._size = 0; 128 129 if (f < 0) { /* did not get it after all */ 130 fp->_flags = 0; /* set it free */ 131 errno = sverrno; /* restore in case _close clobbered */ 132 return (NULL); 133 } 134 135 /* 136 * If reopening something that was open before on a real file, try 137 * to maintain the descriptor. Various C library routines (perror) 138 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 139 */ 140 if (wantfd >= 0 && f != wantfd) { 141 if (dup2(f, wantfd) >= 0) { 142 (void) close(f); 143 f = wantfd; 144 } 145 } 146 147 fp->_flags = flags; 148 fp->_file = f; 149 fp->_cookie = fp; 150 fp->_read = __sread; 151 fp->_write = __swrite; 152 fp->_seek = __sseek; 153 fp->_close = __sclose; 154 return (fp); 155 }