xref: /minix3/lib/libc/stdio/freopen.c (revision f14fb602092e015ff630df58e17c2a9cd57d29b3)
1*f14fb602SLionel Sambuc /*	$NetBSD: freopen.c,v 1.19 2012/03/27 15:05:42 christos Exp $	*/
2b7061124SArun Thomas 
32fe8fb19SBen Gras /*-
42fe8fb19SBen Gras  * Copyright (c) 1990, 1993
52fe8fb19SBen Gras  *	The Regents of the University of California.  All rights reserved.
62fe8fb19SBen Gras  *
72fe8fb19SBen Gras  * This code is derived from software contributed to Berkeley by
82fe8fb19SBen Gras  * Chris Torek.
92fe8fb19SBen Gras  *
102fe8fb19SBen Gras  * Redistribution and use in source and binary forms, with or without
112fe8fb19SBen Gras  * modification, are permitted provided that the following conditions
122fe8fb19SBen Gras  * are met:
132fe8fb19SBen Gras  * 1. Redistributions of source code must retain the above copyright
142fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer.
152fe8fb19SBen Gras  * 2. Redistributions in binary form must reproduce the above copyright
162fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer in the
172fe8fb19SBen Gras  *    documentation and/or other materials provided with the distribution.
182fe8fb19SBen Gras  * 3. Neither the name of the University nor the names of its contributors
192fe8fb19SBen Gras  *    may be used to endorse or promote products derived from this software
202fe8fb19SBen Gras  *    without specific prior written permission.
212fe8fb19SBen Gras  *
222fe8fb19SBen Gras  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
232fe8fb19SBen Gras  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
242fe8fb19SBen Gras  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
252fe8fb19SBen Gras  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
262fe8fb19SBen Gras  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
272fe8fb19SBen Gras  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
282fe8fb19SBen Gras  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
292fe8fb19SBen Gras  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
302fe8fb19SBen Gras  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
312fe8fb19SBen Gras  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
322fe8fb19SBen Gras  * SUCH DAMAGE.
332fe8fb19SBen Gras  */
342fe8fb19SBen Gras 
352fe8fb19SBen Gras #include <sys/cdefs.h>
362fe8fb19SBen Gras #if defined(LIBC_SCCS) && !defined(lint)
372fe8fb19SBen Gras #if 0
382fe8fb19SBen Gras static char sccsid[] = "@(#)freopen.c	8.1 (Berkeley) 6/4/93";
392fe8fb19SBen Gras #else
40*f14fb602SLionel Sambuc __RCSID("$NetBSD: freopen.c,v 1.19 2012/03/27 15:05:42 christos Exp $");
41b7061124SArun Thomas #endif
422fe8fb19SBen Gras #endif /* LIBC_SCCS and not lint */
432fe8fb19SBen Gras 
442fe8fb19SBen Gras #include <sys/types.h>
45b7061124SArun Thomas #include <sys/stat.h>
46b7061124SArun Thomas 
472fe8fb19SBen Gras #include <assert.h>
482fe8fb19SBen Gras #include <errno.h>
492fe8fb19SBen Gras #include <fcntl.h>
502fe8fb19SBen Gras #include <unistd.h>
512fe8fb19SBen Gras #include <stdio.h>
522fe8fb19SBen Gras #include <stdlib.h>
532fe8fb19SBen Gras #include <wchar.h>
542fe8fb19SBen Gras #include <limits.h>
552fe8fb19SBen Gras #include "reentrant.h"
562fe8fb19SBen Gras #include "local.h"
57b7061124SArun Thomas 
582fe8fb19SBen Gras /*
592fe8fb19SBen Gras  * Re-direct an existing, open (probably) file to some other file.
602fe8fb19SBen Gras  * ANSI is written such that the original file gets closed if at
612fe8fb19SBen Gras  * all possible, no matter what.
62b7061124SArun Thomas  */
63b7061124SArun Thomas FILE *
freopen(const char * file,const char * mode,FILE * fp)64*f14fb602SLionel Sambuc freopen(const char *file, const char *mode, FILE *fp)
65b7061124SArun Thomas {
662fe8fb19SBen Gras 	int f;
672fe8fb19SBen Gras 	int flags, isopen, oflags, sverrno, wantfd;
68b7061124SArun Thomas 
692fe8fb19SBen Gras 	_DIAGASSERT(file != NULL);
702fe8fb19SBen Gras 	_DIAGASSERT(mode != NULL);
712fe8fb19SBen Gras 	_DIAGASSERT(fp != NULL);
72b7061124SArun Thomas 
732fe8fb19SBen Gras 	if ((flags = __sflags(mode, &oflags)) == 0) {
742fe8fb19SBen Gras 		(void) fclose(fp);
75*f14fb602SLionel Sambuc 		return NULL;
7651d9144eSBen Gras 	}
7751d9144eSBen Gras 
782fe8fb19SBen Gras 	if (!__sdidinit)
792fe8fb19SBen Gras 		__sinit();
8051d9144eSBen Gras 
812fe8fb19SBen Gras 	/*
822fe8fb19SBen Gras 	 * There are actually programs that depend on being able to "freopen"
832fe8fb19SBen Gras 	 * descriptors that weren't originally open.  Keep this from breaking.
842fe8fb19SBen Gras 	 * Remember whether the stream was open to begin with, and which file
852fe8fb19SBen Gras 	 * descriptor (if any) was associated with it.  If it was attached to
862fe8fb19SBen Gras 	 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
872fe8fb19SBen Gras 	 * should work.  This is unnecessary if it was not a Unix file.
882fe8fb19SBen Gras 	 */
892fe8fb19SBen Gras 	if (fp->_flags == 0) {
902fe8fb19SBen Gras 		fp->_flags = __SEOF;	/* hold on to it */
912fe8fb19SBen Gras 		isopen = 0;
922fe8fb19SBen Gras 		wantfd = -1;
93b7061124SArun Thomas 	} else {
942fe8fb19SBen Gras 		/* flush the stream; ANSI doesn't require this. */
952fe8fb19SBen Gras 		if (fp->_flags & __SWR)
962fe8fb19SBen Gras 			(void)__sflush(fp);
972fe8fb19SBen Gras 		/* if close is NULL, closing is a no-op, hence pointless */
982fe8fb19SBen Gras 		isopen = fp->_close != NULL;
992fe8fb19SBen Gras 		if ((wantfd = __sfileno(fp)) == -1 && isopen) {
1002fe8fb19SBen Gras 			(void) (*fp->_close)(fp->_cookie);
1012fe8fb19SBen Gras 			isopen = 0;
1022fe8fb19SBen Gras 		}
103b7061124SArun Thomas 	}
104b7061124SArun Thomas 
1052fe8fb19SBen Gras 	/* Get a new descriptor to refer to the new file. */
1062fe8fb19SBen Gras 	f = open(file, oflags, DEFFILEMODE);
1072fe8fb19SBen Gras 	if (f < 0 && isopen) {
1082fe8fb19SBen Gras 		/* If out of fd's close the old one and try again. */
1092fe8fb19SBen Gras 		if (errno == ENFILE || errno == EMFILE) {
1102fe8fb19SBen Gras 			(void) (*fp->_close)(fp->_cookie);
1112fe8fb19SBen Gras 			isopen = 0;
1122fe8fb19SBen Gras 			f = open(file, oflags, DEFFILEMODE);
1132fe8fb19SBen Gras 		}
1142fe8fb19SBen Gras 	}
1152fe8fb19SBen Gras 	sverrno = errno;
116b7061124SArun Thomas 
1172fe8fb19SBen Gras 	/*
1182fe8fb19SBen Gras 	 * Finish closing fp.  Even if the open succeeded above, we cannot
1192fe8fb19SBen Gras 	 * keep fp->_base: it may be the wrong size.  This loses the effect
1202fe8fb19SBen Gras 	 * of any setbuffer calls, but stdio has always done this before.
1212fe8fb19SBen Gras 	 */
1222fe8fb19SBen Gras 	if (isopen && f != wantfd)
1232fe8fb19SBen Gras 		(void) (*fp->_close)(fp->_cookie);
1242fe8fb19SBen Gras 	if (fp->_flags & __SMBF)
1252fe8fb19SBen Gras 		free((char *)fp->_bf._base);
1262fe8fb19SBen Gras 	fp->_w = 0;
1272fe8fb19SBen Gras 	fp->_r = 0;
1282fe8fb19SBen Gras 	fp->_p = NULL;
1292fe8fb19SBen Gras 	fp->_bf._base = NULL;
1302fe8fb19SBen Gras 	fp->_bf._size = 0;
1312fe8fb19SBen Gras 	fp->_lbfsize = 0;
1322fe8fb19SBen Gras 	if (HASUB(fp))
1332fe8fb19SBen Gras 		FREEUB(fp);
1342fe8fb19SBen Gras 	WCIO_FREE(fp);
1352fe8fb19SBen Gras 	_UB(fp)._size = 0;
1362fe8fb19SBen Gras 	FREELB(fp);
1372fe8fb19SBen Gras 
1382fe8fb19SBen Gras 	if (f < 0) {			/* did not get it after all */
1392fe8fb19SBen Gras 		fp->_flags = 0;		/* set it free */
1402fe8fb19SBen Gras 		errno = sverrno;	/* restore in case _close clobbered */
141*f14fb602SLionel Sambuc 		return NULL;
1422fe8fb19SBen Gras 	}
1432fe8fb19SBen Gras 
1442fe8fb19SBen Gras 	if (oflags & O_NONBLOCK) {
1452fe8fb19SBen Gras 		struct stat st;
1462fe8fb19SBen Gras 		if (fstat(f, &st) == -1) {
1472fe8fb19SBen Gras 			sverrno = errno;
1482fe8fb19SBen Gras 			(void)close(f);
1492fe8fb19SBen Gras 			errno = sverrno;
150*f14fb602SLionel Sambuc 			return NULL;
1512fe8fb19SBen Gras 		}
1522fe8fb19SBen Gras 		if (!S_ISREG(st.st_mode)) {
1532fe8fb19SBen Gras 			(void)close(f);
1542fe8fb19SBen Gras 			errno = EFTYPE;
155*f14fb602SLionel Sambuc 			return NULL;
1562fe8fb19SBen Gras 		}
1572fe8fb19SBen Gras 	}
1582fe8fb19SBen Gras 
1592fe8fb19SBen Gras 	/*
1602fe8fb19SBen Gras 	 * If reopening something that was open before on a real file, try
1612fe8fb19SBen Gras 	 * to maintain the descriptor.  Various C library routines (perror)
1622fe8fb19SBen Gras 	 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
1632fe8fb19SBen Gras 	 */
1642fe8fb19SBen Gras 	if (wantfd >= 0 && f != wantfd) {
1652fe8fb19SBen Gras 		if (dup2(f, wantfd) >= 0) {
1662fe8fb19SBen Gras 			(void) close(f);
1672fe8fb19SBen Gras 			f = wantfd;
1682fe8fb19SBen Gras 		}
1692fe8fb19SBen Gras 	}
1702fe8fb19SBen Gras 
1712fe8fb19SBen Gras 	/*
1722fe8fb19SBen Gras 	 * File descriptors are a full int, but _file is only a short.
1732fe8fb19SBen Gras 	 * If we get a valid file descriptor that is greater or equal to
1742fe8fb19SBen Gras 	 * USHRT_MAX, then the fd will get sign-extended into an
1752fe8fb19SBen Gras 	 * invalid file descriptor.  Handle this case by failing the
1762fe8fb19SBen Gras 	 * open. (We treat the short as unsigned, and special-case -1).
1772fe8fb19SBen Gras 	 */
1782fe8fb19SBen Gras 	if (f >= USHRT_MAX) {
1792fe8fb19SBen Gras 		(void)close(f);
1802fe8fb19SBen Gras 		errno = EMFILE;
1812fe8fb19SBen Gras 		return NULL;
1822fe8fb19SBen Gras 	}
1832fe8fb19SBen Gras 
1842fe8fb19SBen Gras 	fp->_flags = flags;
1852fe8fb19SBen Gras 	fp->_file = f;
1862fe8fb19SBen Gras 	fp->_cookie = fp;
1872fe8fb19SBen Gras 	fp->_read = __sread;
1882fe8fb19SBen Gras 	fp->_write = __swrite;
1892fe8fb19SBen Gras 	fp->_seek = __sseek;
1902fe8fb19SBen Gras 	fp->_close = __sclose;
1912fe8fb19SBen Gras 
1922fe8fb19SBen Gras 	/*
1932fe8fb19SBen Gras 	 * When reopening in append mode, even though we use O_APPEND,
1942fe8fb19SBen Gras 	 * we need to seek to the end so that ftell() gets the right
1952fe8fb19SBen Gras 	 * answer.  If the user then alters the seek pointer, or
1962fe8fb19SBen Gras 	 * the file extends, this will fail, but there is not much
1972fe8fb19SBen Gras 	 * we can do about this.  (We could set __SAPP and check in
1982fe8fb19SBen Gras 	 * fseek and ftell.)
1992fe8fb19SBen Gras 	 */
2002fe8fb19SBen Gras 	if (oflags & O_APPEND)
201*f14fb602SLionel Sambuc 		(void) __sseek((void *)fp, (off_t)0, SEEK_END);
202*f14fb602SLionel Sambuc 	return fp;
203b7061124SArun Thomas }
204