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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 | * %sccs.include.redist.c% | |
586c39b1 DF |
9 | */ |
10 | ||
2ce81398 | 11 | #if defined(LIBC_SCCS) && !defined(lint) |
cb631443 | 12 | static char sccsid[] = "@(#)freopen.c 5.6 (Berkeley) %G%"; |
411867e7 | 13 | #endif /* LIBC_SCCS and not lint */ |
586c39b1 | 14 | |
41e01b3e | 15 | #include <sys/types.h> |
411867e7 | 16 | #include <sys/stat.h> |
cb631443 | 17 | #include <fcntl.h> |
411867e7 | 18 | #include <errno.h> |
cb631443 | 19 | #include <unistd.h> |
41e01b3e | 20 | #include <stdio.h> |
411867e7 KB |
21 | #include <stdlib.h> |
22 | #include "local.h" | |
2de31004 | 23 | |
411867e7 KB |
24 | /* |
25 | * Re-direct an existing, open (probably) file to some other file. | |
26 | * ANSI is written such that the original file gets closed if at | |
27 | * all possible, no matter what. | |
28 | */ | |
2de31004 | 29 | FILE * |
411867e7 | 30 | freopen(file, mode, fp) |
d25ccb19 | 31 | const char *file, *mode; |
411867e7 | 32 | register FILE *fp; |
2de31004 | 33 | { |
411867e7 KB |
34 | register int f; |
35 | int flags, isopen, oflags, sverrno, wantfd; | |
36 | ||
37 | if ((flags = __sflags(mode, &oflags)) == 0) { | |
38 | (void) fclose(fp); | |
41e01b3e S |
39 | return (NULL); |
40 | } | |
41 | ||
411867e7 KB |
42 | if (!__sdidinit) |
43 | __sinit(); | |
44 | ||
45 | /* | |
46 | * There are actually programs that depend on being able to "freopen" | |
47 | * descriptors that weren't originally open. Keep this from breaking. | |
48 | * Remember whether the stream was open to begin with, and which file | |
49 | * descriptor (if any) was associated with it. If it was attached to | |
50 | * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) | |
51 | * should work. This is unnecessary if it was not a Unix file. | |
52 | */ | |
53 | if (fp->_flags == 0) { | |
54 | fp->_flags = __SEOF; /* hold on to it */ | |
55 | isopen = 0; | |
56 | wantfd = -1; | |
57 | } else { | |
58 | /* flush the stream; ANSI doesn't require this. */ | |
59 | if (fp->_flags & __SWR) | |
1dcadafa | 60 | (void) __sflush(fp); |
411867e7 KB |
61 | /* if close is NULL, closing is a no-op, hence pointless */ |
62 | isopen = fp->_close != NULL; | |
63 | if ((wantfd = fp->_file) < 0 && isopen) { | |
64 | (void) (*fp->_close)(fp->_cookie); | |
65 | isopen = 0; | |
66 | } | |
67 | } | |
68 | ||
69 | /* Get a new descriptor to refer to the new file. */ | |
70 | f = open(file, oflags, DEFFILEMODE); | |
71 | if (f < 0 && isopen) { | |
72 | /* If out of fd's close the old one and try again. */ | |
73 | if (errno == ENFILE || errno == EMFILE) { | |
74 | (void) (*fp->_close)(fp->_cookie); | |
75 | isopen = 0; | |
76 | f = open(file, oflags, DEFFILEMODE); | |
77 | } | |
78 | } | |
79 | sverrno = errno; | |
80 | ||
81 | /* | |
82 | * Finish closing fp. Even if the open succeeded above, we cannot | |
83 | * keep fp->_base: it may be the wrong size. This loses the effect | |
84 | * of any setbuffer calls, but stdio has always done this before. | |
85 | */ | |
86 | if (isopen) | |
87 | (void) (*fp->_close)(fp->_cookie); | |
88 | if (fp->_flags & __SMBF) | |
89 | free((char *)fp->_bf._base); | |
90 | fp->_w = 0; | |
91 | fp->_r = 0; | |
92 | fp->_p = NULL; | |
93 | fp->_bf._base = NULL; | |
94 | fp->_bf._size = 0; | |
95 | fp->_lbfsize = 0; | |
96 | if (HASUB(fp)) | |
97 | FREEUB(fp); | |
98 | fp->_ub._size = 0; | |
99 | if (HASLB(fp)) | |
100 | FREELB(fp); | |
101 | fp->_lb._size = 0; | |
102 | ||
103 | if (f < 0) { /* did not get it after all */ | |
104 | fp->_flags = 0; /* set it free */ | |
105 | errno = sverrno; /* restore in case _close clobbered */ | |
41e01b3e | 106 | return (NULL); |
411867e7 KB |
107 | } |
108 | ||
109 | /* | |
110 | * If reopening something that was open before on a real file, try | |
111 | * to maintain the descriptor. Various C library routines (perror) | |
112 | * assume stderr is always fd STDERR_FILENO, even if being freopen'd. | |
113 | */ | |
114 | if (wantfd >= 0 && f != wantfd) { | |
115 | if (dup2(f, wantfd) >= 0) { | |
116 | (void) close(f); | |
117 | f = wantfd; | |
118 | } | |
119 | } | |
41e01b3e | 120 | |
411867e7 KB |
121 | fp->_flags = flags; |
122 | fp->_file = f; | |
123 | fp->_cookie = fp; | |
124 | fp->_read = __sread; | |
125 | fp->_write = __swrite; | |
126 | fp->_seek = __sseek; | |
127 | fp->_close = __sclose; | |
128 | return (fp); | |
2de31004 | 129 | } |