freopen.c revision 1.4.2.1
1 /* $NetBSD: freopen.c,v 1.4.2.1 1995/03/02 20:23:47 jtc 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 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 42 #endif 43 static char rcsid[] = "$NetBSD: freopen.c,v 1.4.2.1 1995/03/02 20:23:47 jtc Exp $"; 44 #endif /* LIBC_SCCS and not lint */ 45 46 #include "namespace.h" 47 #include <sys/types.h> 48 #include <sys/stat.h> 49 #include <fcntl.h> 50 #include <errno.h> 51 #include <unistd.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include "local.h" 55 56 /* 57 * Re-direct an existing, open (probably) file to some other file. 58 * ANSI is written such that the original file gets closed if at 59 * all possible, no matter what. 60 */ 61 FILE * 62 freopen(file, mode, fp) 63 const char *file, *mode; 64 register FILE *fp; 65 { 66 register int f; 67 int flags, isopen, oflags, sverrno, wantfd; 68 69 if ((flags = __sflags(mode, &oflags)) == 0) { 70 (void) fclose(fp); 71 return (NULL); 72 } 73 74 if (!__sdidinit) 75 __sinit(); 76 77 /* 78 * There are actually programs that depend on being able to "freopen" 79 * descriptors that weren't originally open. Keep this from breaking. 80 * Remember whether the stream was open to begin with, and which file 81 * descriptor (if any) was associated with it. If it was attached to 82 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 83 * should work. This is unnecessary if it was not a Unix file. 84 */ 85 if (fp->_flags == 0) { 86 fp->_flags = __SEOF; /* hold on to it */ 87 isopen = 0; 88 wantfd = -1; 89 } else { 90 /* flush the stream; ANSI doesn't require this. */ 91 if (fp->_flags & __SWR) 92 (void) __sflush(fp); 93 /* if close is NULL, closing is a no-op, hence pointless */ 94 isopen = fp->_close != NULL; 95 if ((wantfd = fp->_file) < 0 && isopen) { 96 (void) (*fp->_close)(fp->_cookie); 97 isopen = 0; 98 } 99 } 100 101 /* Get a new descriptor to refer to the new file. */ 102 f = open(file, oflags, DEFFILEMODE); 103 if (f < 0 && isopen) { 104 /* If out of fd's close the old one and try again. */ 105 if (errno == ENFILE || errno == EMFILE) { 106 (void) (*fp->_close)(fp->_cookie); 107 isopen = 0; 108 f = open(file, oflags, DEFFILEMODE); 109 } 110 } 111 sverrno = errno; 112 113 /* 114 * Finish closing fp. Even if the open succeeded above, we cannot 115 * keep fp->_base: it may be the wrong size. This loses the effect 116 * of any setbuffer calls, but stdio has always done this before. 117 */ 118 if (isopen) 119 (void) (*fp->_close)(fp->_cookie); 120 if (fp->_flags & __SMBF) 121 free((char *)fp->_bf._base); 122 fp->_w = 0; 123 fp->_r = 0; 124 fp->_p = NULL; 125 fp->_bf._base = NULL; 126 fp->_bf._size = 0; 127 fp->_lbfsize = 0; 128 if (HASUB(fp)) 129 FREEUB(fp); 130 fp->_ub._size = 0; 131 if (HASLB(fp)) 132 FREELB(fp); 133 fp->_lb._size = 0; 134 135 if (f < 0) { /* did not get it after all */ 136 fp->_flags = 0; /* set it free */ 137 errno = sverrno; /* restore in case _close clobbered */ 138 return (NULL); 139 } 140 141 /* 142 * If reopening something that was open before on a real file, try 143 * to maintain the descriptor. Various C library routines (perror) 144 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 145 */ 146 if (wantfd >= 0 && f != wantfd) { 147 if (dup2(f, wantfd) >= 0) { 148 (void) close(f); 149 f = wantfd; 150 } 151 } 152 153 fp->_flags = flags; 154 fp->_file = f; 155 fp->_cookie = fp; 156 fp->_read = __sread; 157 fp->_write = __swrite; 158 fp->_seek = __sseek; 159 fp->_close = __sclose; 160 return (fp); 161 } 162
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