1 /*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * 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. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)freopen.c 5.6 (Berkeley) 2/24/91";
39 #endif /* LIBC_SCCS and not lint */
40
41 #include <sys/types.h>
42 #include <sys/stat.h>
43 #include <fcntl.h>
44 #include <errno.h>
45 #include <unistd.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include "local.h"
49
50 /*
51 * Re-direct an existing, open (probably) file to some other file.
52 * ANSI is written such that the original file gets closed if at
53 * all possible, no matter what.
54 */
55 FILE *
freopen(file,mode,fp)56 freopen(file, mode, fp)
57 const char *file, *mode;
58 register FILE *fp;
59 {
60 register int f;
61 int flags, isopen, oflags, sverrno, wantfd;
62
63 if ((flags = __sflags(mode, &oflags)) == 0) {
64 (void) fclose(fp);
65 return (NULL);
66 }
67
68 if (!__sdidinit)
69 __sinit();
70
71 /*
72 * There are actually programs that depend on being able to "freopen"
73 * descriptors that weren't originally open. Keep this from breaking.
74 * Remember whether the stream was open to begin with, and which file
75 * descriptor (if any) was associated with it. If it was attached to
76 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
77 * should work. This is unnecessary if it was not a Unix file.
78 */
79 if (fp->_flags == 0) {
80 fp->_flags = __SEOF; /* hold on to it */
81 isopen = 0;
82 wantfd = -1;
83 } else {
84 /* flush the stream; ANSI doesn't require this. */
85 if (fp->_flags & __SWR)
86 (void) __sflush(fp);
87 /* if close is NULL, closing is a no-op, hence pointless */
88 isopen = fp->_close != NULL;
89 if ((wantfd = fp->_file) < 0 && isopen) {
90 (void) (*fp->_close)(fp->_cookie);
91 isopen = 0;
92 }
93 }
94
95 /* Get a new descriptor to refer to the new file. */
96 f = open(file, oflags, DEFFILEMODE);
97 if (f < 0 && isopen) {
98 /* If out of fd's close the old one and try again. */
99 if (errno == ENFILE || errno == EMFILE) {
100 (void) (*fp->_close)(fp->_cookie);
101 isopen = 0;
102 f = open(file, oflags, DEFFILEMODE);
103 }
104 }
105 sverrno = errno;
106
107 /*
108 * Finish closing fp. Even if the open succeeded above, we cannot
109 * keep fp->_base: it may be the wrong size. This loses the effect
110 * of any setbuffer calls, but stdio has always done this before.
111 */
112 if (isopen)
113 (void) (*fp->_close)(fp->_cookie);
114 if (fp->_flags & __SMBF)
115 free((char *)fp->_bf._base);
116 fp->_w = 0;
117 fp->_r = 0;
118 fp->_p = NULL;
119 fp->_bf._base = NULL;
120 fp->_bf._size = 0;
121 fp->_lbfsize = 0;
122 if (HASUB(fp))
123 FREEUB(fp);
124 fp->_ub._size = 0;
125 if (HASLB(fp))
126 FREELB(fp);
127 fp->_lb._size = 0;
128
129 if (f < 0) { /* did not get it after all */
130 fp->_flags = 0; /* set it free */
131 errno = sverrno; /* restore in case _close clobbered */
132 return (NULL);
133 }
134
135 /*
136 * If reopening something that was open before on a real file, try
137 * to maintain the descriptor. Various C library routines (perror)
138 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
139 */
140 if (wantfd >= 0 && f != wantfd) {
141 if (dup2(f, wantfd) >= 0) {
142 (void) close(f);
143 f = wantfd;
144 }
145 }
146
147 fp->_flags = flags;
148 fp->_file = f;
149 fp->_cookie = fp;
150 fp->_read = __sread;
151 fp->_write = __swrite;
152 fp->_seek = __sseek;
153 fp->_close = __sclose;
154 return (fp);
155 }
156