1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)freopen.c 8.1 (Berkeley) 6/4/93
33 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.21 2008/04/17 22:17:54 jhb Exp $
34 */
35
36 #include "namespace.h"
37 #include <sys/types.h>
38 #include <sys/stat.h>
39 #include <fcntl.h>
40 #include <errno.h>
41 #include <unistd.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include "un-namespace.h"
45 #include "libc_private.h"
46 #include "local.h"
47
48 /*
49 * Re-direct an existing, open (probably) file to some other file.
50 * ANSI is written such that the original file gets closed if at
51 * all possible, no matter what.
52 */
53 FILE *
freopen(const char * __restrict file,const char * __restrict mode,FILE * fp)54 freopen(const char * __restrict file, const char * __restrict mode, FILE *fp)
55 {
56 int f;
57 int dflags, flags, isopen, oflags, sverrno, wantfd;
58
59 if ((flags = __sflags(mode, &oflags)) == 0) {
60 sverrno = errno;
61 fclose(fp);
62 errno = sverrno;
63 return (NULL);
64 }
65
66 FLOCKFILE(fp);
67
68 if (!__sdidinit)
69 __sinit();
70
71 /*
72 * If the filename is a NULL pointer, the caller is asking us to
73 * re-open the same file with a different mode. We allow this only
74 * if the modes are compatible.
75 */
76 if (file == NULL) {
77 /* See comment below regarding freopen() of closed files. */
78 if (fp->pub._flags == 0) {
79 FUNLOCKFILE(fp);
80 errno = EINVAL;
81 return (NULL);
82 }
83 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) {
84 sverrno = errno;
85 fclose(fp);
86 FUNLOCKFILE(fp);
87 errno = sverrno;
88 return (NULL);
89 }
90 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
91 (oflags & O_ACCMODE)) {
92 fclose(fp);
93 FUNLOCKFILE(fp);
94 errno = EINVAL;
95 return (NULL);
96 }
97 if (fp->pub._flags & __SWR)
98 __sflush(fp);
99 if ((oflags ^ dflags) & O_APPEND) {
100 dflags &= ~O_APPEND;
101 dflags |= oflags & O_APPEND;
102 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) {
103 sverrno = errno;
104 fclose(fp);
105 FUNLOCKFILE(fp);
106 errno = sverrno;
107 return (NULL);
108 }
109 }
110 if (oflags & O_TRUNC)
111 ftruncate(fp->pub._fileno, (off_t)0);
112 if (!(oflags & O_APPEND))
113 _sseek(fp, (fpos_t)0, SEEK_SET);
114 if (oflags & O_CLOEXEC)
115 _fcntl(fileno(fp), F_SETFD, FD_CLOEXEC);
116
117 f = fp->pub._fileno;
118 isopen = 0;
119 wantfd = -1;
120 goto finish;
121 }
122
123 /*
124 * There are actually programs that depend on being able to "freopen"
125 * descriptors that weren't originally open. Keep this from breaking.
126 * Remember whether the stream was open to begin with, and which file
127 * descriptor (if any) was associated with it. If it was attached to
128 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
129 * should work. This is unnecessary if it was not a Unix file.
130 */
131 if (fp->pub._flags == 0) {
132 fp->pub._flags = __SEOF; /* hold on to it */
133 isopen = 0;
134 wantfd = -1;
135 } else {
136 /* flush the stream; ANSI doesn't require this. */
137 if (fp->pub._flags & __SWR)
138 __sflush(fp);
139 /* if close is NULL, closing is a no-op, hence pointless */
140 isopen = fp->_close != NULL;
141 if ((wantfd = fp->pub._fileno) < 0 && isopen) {
142 (*fp->_close)(fp->_cookie);
143 isopen = 0;
144 }
145 }
146
147 /* Get a new descriptor to refer to the new file. */
148 f = _open(file, oflags, DEFFILEMODE);
149 if (f < 0 && isopen) {
150 /* If out of fd's close the old one and try again. */
151 if (errno == ENFILE || errno == EMFILE) {
152 (*fp->_close)(fp->_cookie);
153 isopen = 0;
154 f = _open(file, oflags, DEFFILEMODE);
155 }
156 }
157 sverrno = errno;
158
159 finish:
160 /*
161 * Finish closing fp. Even if the open succeeded above, we cannot
162 * keep fp->_base: it may be the wrong size. This loses the effect
163 * of any setbuffer calls, but stdio has always done this before.
164 */
165 if (isopen)
166 (*fp->_close)(fp->_cookie);
167 if (fp->pub._flags & __SMBF)
168 free((char *)fp->_bf._base);
169 fp->pub._w = 0;
170 fp->pub._r = 0;
171 fp->pub._p = NULL;
172 fp->_bf._base = NULL;
173 fp->_bf._size = 0;
174 fp->pub._lbfsize = 0;
175 if (HASUB(fp))
176 FREEUB(fp);
177 fp->_ub._size = 0;
178 if (HASLB(fp))
179 FREELB(fp);
180 fp->_lb._size = 0;
181 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
182
183 if (f < 0) { /* did not get it after all */
184 fp->pub._flags = 0; /* set it free */
185 FUNLOCKFILE(fp);
186 errno = sverrno; /* restore in case _close clobbered */
187 return (NULL);
188 }
189
190 /*
191 * If reopening something that was open before on a real file, try
192 * to maintain the descriptor. Various C library routines (perror)
193 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
194 */
195 if (wantfd >= 0 && f != wantfd) {
196 if (oflags & O_CLOEXEC) {
197 if (_fcntl(f, F_DUP2FD_CLOEXEC, wantfd) >= 0) {
198 _close(f);
199 f = wantfd;
200 }
201 } else {
202 if (_dup2(f, wantfd) >= 0) {
203 _close(f);
204 f = wantfd;
205 }
206 }
207 }
208
209 fp->pub._flags = flags;
210 fp->pub._fileno = f;
211 fp->_cookie = fp;
212 fp->_read = __sread;
213 fp->_write = __swrite;
214 fp->_seek = __sseek;
215 fp->_close = __sclose;
216 /*
217 * When opening in append mode, even though we use O_APPEND,
218 * we need to seek to the end so that ftell() gets the right
219 * answer. If the user then alters the seek pointer, or
220 * the file extends, this will fail, but there is not much
221 * we can do about this. (We could set __SAPP and check in
222 * fseek and ftell.)
223 */
224 if (oflags & O_APPEND)
225 _sseek(fp, (fpos_t)0, SEEK_END);
226 FUNLOCKFILE(fp);
227 return (fp);
228 }
229