1/* $NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35#include <sys/cdefs.h> 36#if defined(LIBC_SCCS) && !defined(lint) 37#if 0 38static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 39#else 40__RCSID("$NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil Exp $"); 41#endif 42#endif /* LIBC_SCCS and not lint */ 43 44#include <sys/types.h> 45#include <sys/stat.h> 46 47#include <assert.h> 48#include <errno.h> 49#include <fcntl.h> 50#include <unistd.h> 51#include <stdio.h> 52#include <stdlib.h> 53#include <wchar.h> 54#include <limits.h> 55#include "reentrant.h" 56#include "local.h" 57 58/* 59 * Re-direct an existing, open (probably) file to some other file. 60 * ANSI is written such that the original file gets closed if at 61 * all possible, no matter what. 62 */ 63FILE * 64freopen(const char *file, const char *mode, FILE *fp) 65{ 66 int f; 67 int flags, isopen, oflags, sverrno, wantfd; 68 69 _DIAGASSERT(file != NULL); 70 _DIAGASSERT(mode != NULL); 71 _DIAGASSERT(fp != NULL); 72 73 if ((flags = __sflags(mode, &oflags)) == 0) { 74 (void) fclose(fp); 75 return NULL; 76 } 77 78 if (!__sdidinit) 79 __sinit(); 80 81 /* 82 * There are actually programs that depend on being able to "freopen" 83 * descriptors that weren't originally open. Keep this from breaking. 84 * Remember whether the stream was open to begin with, and which file 85 * descriptor (if any) was associated with it. If it was attached to 86 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 87 * should work. This is unnecessary if it was not a Unix file. 88 */ 89 if (fp->_flags == 0) { 90 fp->_flags = __SEOF; /* hold on to it */ 91 isopen = 0; 92 wantfd = -1; 93 } else { 94 /* flush the stream; ANSI doesn't require this. */ 95 if (fp->_flags & __SWR) 96 (void)__sflush(fp); 97 /* if close is NULL, closing is a no-op, hence pointless */ 98 isopen = fp->_close != NULL; 99 if ((wantfd = __sfileno(fp)) == -1 && isopen) { 100 (void) (*fp->_close)(fp->_cookie); 101 isopen = 0; 102 } 103 } 104 105 /* Get a new descriptor to refer to the new file. */ 106 f = open(file, oflags, DEFFILEMODE); 107 if (f < 0 && isopen) { 108 /* If out of fd's close the old one and try again. */ 109 if (errno == ENFILE || errno == EMFILE) { 110 (void) (*fp->_close)(fp->_cookie); 111 isopen = 0; 112 f = open(file, oflags, DEFFILEMODE); 113 } 114 } 115 sverrno = errno; 116 117 /* 118 * Finish closing fp. Even if the open succeeded above, we cannot 119 * keep fp->_base: it may be the wrong size. This loses the effect 120 * of any setbuffer calls, but stdio has always done this before. 121 */ 122 if (isopen && f != wantfd) 123 (void) (*fp->_close)(fp->_cookie); 124 if (fp->_flags & __SMBF) 125 free((char *)fp->_bf._base); 126 fp->_w = 0; 127 fp->_r = 0; 128 fp->_p = NULL; 129 fp->_bf._base = NULL; 130 fp->_bf._size = 0; 131 fp->_lbfsize = 0; 132 if (HASUB(fp)) 133 FREEUB(fp); 134 WCIO_FREE(fp); 135 _UB(fp)._size = 0; 136 FREELB(fp); 137 138 if (f < 0) { /* did not get it after all */ 139 fp->_flags = 0; /* set it free */ 140 errno = sverrno; /* restore in case _close clobbered */ 141 return NULL; 142 } 143 144 /* 145 * If reopening something that was open before on a real file, try 146 * to maintain the descriptor. Various C library routines (perror) 147 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 148 */ 149 if (wantfd >= 0 && f != wantfd) { 150 if (dup2(f, wantfd) >= 0) { 151 (void) close(f); 152 f = wantfd; 153 } 154 } 155 156 /* 157 * File descriptors are a full int, but _file is only a short. 158 * If we get a valid file descriptor that is greater or equal to 159 * USHRT_MAX, then the fd will get sign-extended into an 160 * invalid file descriptor. Handle this case by failing the 161 * open. (We treat the short as unsigned, and special-case -1). 162 */ 163 if (f >= USHRT_MAX) { 164 (void)close(f); 165 errno = EMFILE; 166 return NULL; 167 } 168 169 fp->_flags = flags; 170 fp->_file = f; 171 fp->_cookie = fp; 172 fp->_read = __sread; 173 fp->_write = __swrite; 174 fp->_seek = __sseek; 175 fp->_close = __sclose; 176 177 /* 178 * When reopening in append mode, even though we use O_APPEND, 179 * we need to seek to the end so that ftell() gets the right 180 * answer. If the user then alters the seek pointer, or 181 * the file extends, this will fail, but there is not much 182 * we can do about this. (We could set __SAPP and check in 183 * fseek and ftell.) 184 */ 185 if (oflags & O_APPEND) 186 (void) __sseek((void *)fp, (off_t)0, SEEK_END); 187 return fp; 188} 189