/* $NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil Exp $ */ /*- * Copyright (c) 1990, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Chris Torek. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/cdefs.h> #if defined(LIBC_SCCS) && !defined(lint) #if 0 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93"; #else __RCSID("$NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil Exp $"); #endif #endif /* LIBC_SCCS and not lint */ #include <sys/types.h> #include <sys/stat.h> #include <assert.h> #include <errno.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <wchar.h> #include <limits.h> #include "reentrant.h" #include "local.h" /* * Re-direct an existing, open (probably) file to some other file. * ANSI is written such that the original file gets closed if at * all possible, no matter what. */ FILE * freopen(const char *file, const char *mode, FILE *fp) { int f; int flags, isopen, oflags, sverrno, wantfd; _DIAGASSERT(file != NULL); _DIAGASSERT(mode != NULL); _DIAGASSERT(fp != NULL); if ((flags = __sflags(mode, &oflags)) == 0) { (void) fclose(fp); return NULL; } if (!__sdidinit) __sinit(); /* * There are actually programs that depend on being able to "freopen" * descriptors that weren't originally open. Keep this from breaking. * Remember whether the stream was open to begin with, and which file * descriptor (if any) was associated with it. If it was attached to * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) * should work. This is unnecessary if it was not a Unix file. */ if (fp->_flags == 0) { fp->_flags = __SEOF; /* hold on to it */ isopen = 0; wantfd = -1; } else { /* flush the stream; ANSI doesn't require this. */ if (fp->_flags & __SWR) (void)__sflush(fp); /* if close is NULL, closing is a no-op, hence pointless */ isopen = fp->_close != NULL; if ((wantfd = __sfileno(fp)) == -1 && isopen) { (void) (*fp->_close)(fp->_cookie); isopen = 0; } } /* Get a new descriptor to refer to the new file. */ f = open(file, oflags, DEFFILEMODE); if (f < 0 && isopen) { /* If out of fd's close the old one and try again. */ if (errno == ENFILE || errno == EMFILE) { (void) (*fp->_close)(fp->_cookie); isopen = 0; f = open(file, oflags, DEFFILEMODE); } } sverrno = errno; /* * Finish closing fp. Even if the open succeeded above, we cannot * keep fp->_base: it may be the wrong size. This loses the effect * of any setbuffer calls, but stdio has always done this before. */ if (isopen && f != wantfd) (void) (*fp->_close)(fp->_cookie); if (fp->_flags & __SMBF) free((char *)fp->_bf._base); fp->_w = 0; fp->_r = 0; fp->_p = NULL; fp->_bf._base = NULL; fp->_bf._size = 0; fp->_lbfsize = 0; if (HASUB(fp)) FREEUB(fp); WCIO_FREE(fp); _UB(fp)._size = 0; FREELB(fp); if (f < 0) { /* did not get it after all */ fp->_flags = 0; /* set it free */ errno = sverrno; /* restore in case _close clobbered */ return NULL; } /* * If reopening something that was open before on a real file, try * to maintain the descriptor. Various C library routines (perror) * assume stderr is always fd STDERR_FILENO, even if being freopen'd. */ if (wantfd >= 0 && f != wantfd) { if (dup2(f, wantfd) >= 0) { (void) close(f); f = wantfd; } } /* * File descriptors are a full int, but _file is only a short. * If we get a valid file descriptor that is greater or equal to * USHRT_MAX, then the fd will get sign-extended into an * invalid file descriptor. Handle this case by failing the * open. (We treat the short as unsigned, and special-case -1). */ if (f >= USHRT_MAX) { (void)close(f); errno = EMFILE; return NULL; } fp->_flags = flags; fp->_file = f; fp->_cookie = fp; fp->_read = __sread; fp->_write = __swrite; fp->_seek = __sseek; fp->_close = __sclose; /* * When reopening in append mode, even though we use O_APPEND, * we need to seek to the end so that ftell() gets the right * answer. If the user then alters the seek pointer, or * the file extends, this will fail, but there is not much * we can do about this. (We could set __SAPP and check in * fseek and ftell.) */ if (oflags & O_APPEND) (void) __sseek((void *)fp, (off_t)0, SEEK_END); return fp; }
