1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include "namespace.h"
39 #include <sys/types.h>
40 #include <sys/stat.h>
41 #include <fcntl.h>
42 #include <errno.h>
43 #include <limits.h>
44 #include <unistd.h>
45 #include <stdio.h>
46 #include <stdlib.h>
47 #include "un-namespace.h"
48 #include "libc_private.h"
49 #include "local.h"
50
51 /*
52 * Re-direct an existing, open (probably) file to some other file.
53 * ANSI is written such that the original file gets closed if at
54 * all possible, no matter what.
55 */
56 FILE *
freopen(const char * __restrict file,const char * __restrict mode,FILE * __restrict fp)57 freopen(const char * __restrict file, const char * __restrict mode,
58 FILE * __restrict fp)
59 {
60 int f;
61 int dflags, flags, isopen, oflags, sverrno, wantfd;
62
63 if ((flags = __sflags(mode, &oflags)) == 0) {
64 sverrno = errno;
65 (void) fclose(fp);
66 errno = sverrno;
67 return (NULL);
68 }
69
70 FLOCKFILE_CANCELSAFE(fp);
71
72 if (!__sdidinit)
73 __sinit();
74
75 /*
76 * If the filename is a NULL pointer, the caller is asking us to
77 * re-open the same file with a different mode. We allow this only
78 * if the modes are compatible.
79 */
80 if (file == NULL) {
81 /* See comment below regarding freopen() of closed files. */
82 if (fp->_flags == 0) {
83 errno = EINVAL;
84 fp = NULL;
85 goto end;
86 }
87 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
88 sverrno = errno;
89 fclose(fp);
90 errno = sverrno;
91 fp = NULL;
92 goto end;
93 }
94 /* Work around incorrect O_ACCMODE. */
95 if ((dflags & O_ACCMODE) != O_RDWR &&
96 (dflags & (O_ACCMODE | O_EXEC)) != (oflags & O_ACCMODE)) {
97 fclose(fp);
98 errno = EBADF;
99 fp = NULL;
100 goto end;
101 }
102 if (fp->_flags & __SWR)
103 (void) __sflush(fp);
104 if ((oflags ^ dflags) & O_APPEND) {
105 dflags &= ~O_APPEND;
106 dflags |= oflags & O_APPEND;
107 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
108 sverrno = errno;
109 fclose(fp);
110 errno = sverrno;
111 fp = NULL;
112 goto end;
113 }
114 }
115 if (oflags & O_TRUNC)
116 (void) ftruncate(fp->_file, (off_t)0);
117 if (!(oflags & O_APPEND))
118 (void) _sseek(fp, (fpos_t)0, SEEK_SET);
119 if (oflags & O_CLOEXEC)
120 (void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC);
121 f = fp->_file;
122 isopen = 0;
123 wantfd = -1;
124 goto finish;
125 }
126
127 /*
128 * There are actually programs that depend on being able to "freopen"
129 * descriptors that weren't originally open. Keep this from breaking.
130 * Remember whether the stream was open to begin with, and which file
131 * descriptor (if any) was associated with it. If it was attached to
132 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
133 * should work. This is unnecessary if it was not a Unix file.
134 */
135 if (fp->_flags == 0) {
136 fp->_flags = __SEOF; /* hold on to it */
137 isopen = 0;
138 wantfd = -1;
139 } else {
140 /* flush the stream; ANSI doesn't require this. */
141 if (fp->_flags & __SWR)
142 (void) __sflush(fp);
143 /* if close is NULL, closing is a no-op, hence pointless */
144 isopen = fp->_close != NULL;
145 if ((wantfd = fp->_file) < 0 && isopen) {
146 (void) (*fp->_close)(fp->_cookie);
147 isopen = 0;
148 }
149 }
150
151 /* Get a new descriptor to refer to the new file. */
152 f = _open(file, oflags, DEFFILEMODE);
153 /* If out of fd's close the old one and try again. */
154 if (f < 0 && isopen && wantfd > STDERR_FILENO &&
155 (errno == ENFILE || errno == EMFILE)) {
156 (void) (*fp->_close)(fp->_cookie);
157 isopen = 0;
158 wantfd = -1;
159 f = _open(file, oflags, DEFFILEMODE);
160 }
161 sverrno = errno;
162
163 finish:
164 /*
165 * Finish closing fp. Even if the open succeeded above, we cannot
166 * keep fp->_base: it may be the wrong size. This loses the effect
167 * of any setbuffer calls, but stdio has always done this before.
168 *
169 * Leave the existing file descriptor open until dup2() is called
170 * below to avoid races where a concurrent open() in another thread
171 * could claim the existing descriptor.
172 */
173 if (fp->_flags & __SMBF)
174 free((char *)fp->_bf._base);
175 fp->_w = 0;
176 fp->_r = 0;
177 fp->_p = NULL;
178 fp->_bf._base = NULL;
179 fp->_bf._size = 0;
180 fp->_lbfsize = 0;
181 if (HASUB(fp))
182 FREEUB(fp);
183 fp->_ub._size = 0;
184 if (HASLB(fp))
185 FREELB(fp);
186 fp->_lb._size = 0;
187 fp->_orientation = 0;
188 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
189 fp->_flags2 = 0;
190
191 if (f < 0) { /* did not get it after all */
192 if (isopen)
193 (void) (*fp->_close)(fp->_cookie);
194 fp->_flags = 0; /* set it free */
195 errno = sverrno; /* restore in case _close clobbered */
196 fp = NULL;
197 goto end;
198 }
199
200 /*
201 * If reopening something that was open before on a real file, try
202 * to maintain the descriptor. Various C library routines (perror)
203 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
204 */
205 if (wantfd >= 0) {
206 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) :
207 _dup2(f, wantfd)) >= 0) {
208 (void)_close(f);
209 f = wantfd;
210 } else
211 (void)_close(fp->_file);
212 }
213
214 /*
215 * File descriptors are a full int, but _file is only a short.
216 * If we get a valid file descriptor that is greater than
217 * SHRT_MAX, then the fd will get sign-extended into an
218 * invalid file descriptor. Handle this case by failing the
219 * open.
220 */
221 if (f > SHRT_MAX) {
222 fp->_flags = 0; /* set it free */
223 errno = EMFILE;
224 fp = NULL;
225 goto end;
226 }
227
228 fp->_flags = flags;
229 fp->_file = f;
230 fp->_cookie = fp;
231 fp->_read = __sread;
232 fp->_write = __swrite;
233 fp->_seek = __sseek;
234 fp->_close = __sclose;
235 /*
236 * When opening in append mode, even though we use O_APPEND,
237 * we need to seek to the end so that ftell() gets the right
238 * answer. If the user then alters the seek pointer, or
239 * the file extends, this will fail, but there is not much
240 * we can do about this. (We could set __SAPP and check in
241 * fseek and ftell.)
242 */
243 if (oflags & O_APPEND) {
244 fp->_flags2 |= __S2OAP;
245 (void) _sseek(fp, (fpos_t)0, SEEK_END);
246 }
247 end:
248 FUNLOCKFILE_CANCELSAFE();
249 return (fp);
250 }
251