1 /* $NetBSD: freopen.c,v 1.21 2018/01/05 19:01:36 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 38 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; 39 #else 40 __RCSID("$NetBSD: freopen.c,v 1.21 2018/01/05 19:01:36 kamil Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 #include "namespace.h" 45 #include <sys/types.h> 46 #include <sys/stat.h> 47 48 #include <assert.h> 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <unistd.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <wchar.h> 55 #include <limits.h> 56 #include "reentrant.h" 57 #include "local.h" 58 59 /* 60 * Re-direct an existing, open (probably) file to some other file. 61 * ANSI is written such that the original file gets closed if at 62 * all possible, no matter what. 63 */ 64 FILE * 65 freopen(const char *file, const char *mode, FILE *fp) 66 { 67 int f; 68 int flags, isopen, oflags, sverrno, wantfd; 69 70 _DIAGASSERT(file != NULL); 71 _DIAGASSERT(mode != NULL); 72 _DIAGASSERT(fp != NULL); 73 74 if ((flags = __sflags(mode, &oflags)) == 0) { 75 (void) fclose(fp); 76 return NULL; 77 } 78 79 if (!__sdidinit) 80 __sinit(); 81 82 /* 83 * There are actually programs that depend on being able to "freopen" 84 * descriptors that weren't originally open. Keep this from breaking. 85 * Remember whether the stream was open to begin with, and which file 86 * descriptor (if any) was associated with it. If it was attached to 87 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) 88 * should work. This is unnecessary if it was not a Unix file. 89 */ 90 if (fp->_flags == 0) { 91 fp->_flags = __SEOF; /* hold on to it */ 92 isopen = 0; 93 wantfd = -1; 94 } else { 95 /* flush the stream; ANSI doesn't require this. */ 96 if (fp->_flags & __SWR) 97 (void)__sflush(fp); 98 /* if close is NULL, closing is a no-op, hence pointless */ 99 isopen = fp->_close != NULL; 100 if ((wantfd = __sfileno(fp)) == -1 && isopen) { 101 (void) (*fp->_close)(fp->_cookie); 102 isopen = 0; 103 } 104 } 105 106 /* Get a new descriptor to refer to the new file. */ 107 f = open(file, oflags, DEFFILEMODE); 108 if (f < 0 && isopen) { 109 /* If out of fd's close the old one and try again. */ 110 if (errno == ENFILE || errno == EMFILE) { 111 (void) (*fp->_close)(fp->_cookie); 112 isopen = 0; 113 f = open(file, oflags, DEFFILEMODE); 114 } 115 } 116 sverrno = errno; 117 118 /* 119 * Finish closing fp. Even if the open succeeded above, we cannot 120 * keep fp->_base: it may be the wrong size. This loses the effect 121 * of any setbuffer calls, but stdio has always done this before. 122 */ 123 if (isopen && f != wantfd) 124 (void) (*fp->_close)(fp->_cookie); 125 if (fp->_flags & __SMBF) 126 free((char *)fp->_bf._base); 127 fp->_w = 0; 128 fp->_r = 0; 129 fp->_p = NULL; 130 fp->_bf._base = NULL; 131 fp->_bf._size = 0; 132 fp->_lbfsize = 0; 133 if (HASUB(fp)) 134 FREEUB(fp); 135 WCIO_FREE(fp); 136 _UB(fp)._size = 0; 137 FREELB(fp); 138 139 if (f < 0) { /* did not get it after all */ 140 fp->_flags = 0; /* set it free */ 141 errno = sverrno; /* restore in case _close clobbered */ 142 return NULL; 143 } 144 145 /* 146 * If reopening something that was open before on a real file, try 147 * to maintain the descriptor. Various C library routines (perror) 148 * assume stderr is always fd STDERR_FILENO, even if being freopen'd. 149 */ 150 if (wantfd >= 0 && f != wantfd) { 151 if (dup2(f, wantfd) >= 0) { 152 (void) close(f); 153 f = wantfd; 154 } 155 } 156 157 /* 158 * File descriptors are a full int, but _file is only a short. 159 * If we get a valid file descriptor that is greater or equal to 160 * USHRT_MAX, then the fd will get sign-extended into an 161 * invalid file descriptor. Handle this case by failing the 162 * open. (We treat the short as unsigned, and special-case -1). 163 */ 164 if (f >= USHRT_MAX) { 165 (void)close(f); 166 errno = EMFILE; 167 return NULL; 168 } 169 170 fp->_flags = flags; 171 fp->_file = f; 172 fp->_cookie = fp; 173 fp->_read = __sread; 174 fp->_write = __swrite; 175 fp->_seek = __sseek; 176 fp->_close = __sclose; 177 178 /* 179 * When reopening in append mode, even though we use O_APPEND, 180 * we need to seek to the end so that ftell() gets the right 181 * answer. If the user then alters the seek pointer, or 182 * the file extends, this will fail, but there is not much 183 * we can do about this. (We could set __SAPP and check in 184 * fseek and ftell.) 185 */ 186 if (oflags & O_APPEND) 187 (void) __sseek((void *)fp, (off_t)0, SEEK_END); 188 return fp; 189 } 190