1 /*
2 * Copyright (c) 1990 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are permitted
6 * provided that the above copyright notice and this paragraph are
7 * duplicated in all such forms and that any documentation,
8 * and/or other materials related to such
9 * distribution and use acknowledge that the software was developed
10 * by the University of California, Berkeley. The name of the
11 * University may not be used to endorse or promote products derived
12 * from this software without specific prior written permission.
13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16 */
17
18 /*
19 FUNCTION
20 <<fopen>>---open a file
21
22 INDEX
23 fopen
24 INDEX
25 _fopen_r
26
27 SYNOPSIS
28 #include <stdio.h>
29 FILE *fopen(const char *<[file]>, const char *<[mode]>);
30
31 FILE *fopen(
32 const char *<[file]>, const char *<[mode]>);
33
34 DESCRIPTION
35 <<fopen>> initializes the data structures needed to read or write a
36 file. Specify the file's name as the string at <[file]>, and the kind
37 of access you need to the file with the string at <[mode]>.
38
39 The alternate function <<_fopen_r>> is a reentrant version.
40 The extra argument <[reent]> is a pointer to a reentrancy structure.
41
42 Three fundamental kinds of access are available: read, write, and append.
43 <<*<[mode]>>> must begin with one of the three characters `<<r>>',
44 `<<w>>', or `<<a>>', to select one of these:
45
46 o+
47 o r
48 Open the file for reading; the operation will fail if the file does
49 not exist, or if the host system does not permit you to read it.
50
51 o w
52 Open the file for writing @emph{from the beginning} of the file:
53 effectively, this always creates a new file. If the file whose name you
54 specified already existed, its old contents are discarded.
55
56 o a
57 Open the file for appending data, that is writing from the end of
58 file. When you open a file this way, all data always goes to the
59 current end of file; you cannot change this using <<fseek>>.
60 o-
61
62 Some host systems distinguish between ``binary'' and ``text'' files.
63 Such systems may perform data transformations on data written to, or
64 read from, files opened as ``text''.
65 If your system is one of these, then you can append a `<<b>>' to any
66 of the three modes above, to specify that you are opening the file as
67 a binary file (the default is to open the file as a text file).
68
69 `<<rb>>', then, means ``read binary''; `<<wb>>', ``write binary''; and
70 `<<ab>>', ``append binary''.
71
72 To make C programs more portable, the `<<b>>' is accepted on all
73 systems, whether or not it makes a difference.
74
75 Finally, you might need to both read and write from the same file.
76 You can also append a `<<+>>' to any of the three modes, to permit
77 this. (If you want to append both `<<b>>' and `<<+>>', you can do it
78 in either order: for example, <<"rb+">> means the same thing as
79 <<"r+b">> when used as a mode string.)
80
81 Use <<"r+">> (or <<"rb+">>) to permit reading and writing anywhere in
82 an existing file, without discarding any data; <<"w+">> (or <<"wb+">>)
83 to create a new file (or begin by discarding all data from an old one)
84 that permits reading and writing anywhere in it; and <<"a+">> (or
85 <<"ab+">>) to permit reading anywhere in an existing file, but writing
86 only at the end.
87
88 RETURNS
89 <<fopen>> returns a file pointer which you can use for other file
90 operations, unless the file you requested could not be opened; in that
91 situation, the result is <<NULL>>. If the reason for failure was an
92 invalid string at <[mode]>, <<errno>> is set to <<EINVAL>>.
93
94 PORTABILITY
95 <<fopen>> is required by ANSI C.
96
97 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
98 <<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
99 */
100
101 #if defined(LIBC_SCCS) && !defined(lint)
102 static char sccsid[] = "%W% (Berkeley) %G%";
103 #endif /* LIBC_SCCS and not lint */
104
105 #define _DEFAULT_SOURCE
106 #include <_ansi.h>
107 #include <stdio.h>
108 #include <errno.h>
109 #include <unistd.h>
110 #include <sys/lock.h>
111 #include <sys/types.h>
112 #include <sys/stat.h>
113 #include <fcntl.h>
114 #include "local.h"
115
116 FILE *
fopen(const char * __restrict file,const char * __restrict mode)117 fopen (
118 const char *__restrict file,
119 const char *__restrict mode)
120 {
121 register FILE *fp;
122 register int f;
123 int flags, oflags;
124
125 if ((flags = __sflags (mode, &oflags)) == 0)
126 return NULL;
127 if ((fp = __sfp ()) == NULL)
128 return NULL;
129
130 if ((f = open (file, oflags, 0666)) < 0)
131 {
132 _newlib_sfp_lock_start ();
133 fp->_flags = 0; /* release */
134 #ifndef __SINGLE_THREAD__
135 __lock_close_recursive (fp->_lock);
136 #endif
137 _newlib_sfp_lock_end ();
138 return NULL;
139 }
140
141 _newlib_flockfile_start (fp);
142
143 fp->_file = f;
144 fp->_flags = flags;
145 fp->_cookie = (void *) fp;
146 fp->_read = __sread;
147 fp->_write = __swrite;
148 fp->_seek = __sseek;
149 fp->_close = __sclose;
150
151 if (fp->_flags & __SAPP)
152 fseek ( fp, 0, SEEK_END);
153
154 #ifdef __SCLE
155 if (__stextmode (fp->_file))
156 fp->_flags |= __SCLE;
157 #endif
158
159 _newlib_flockfile_end (fp);
160 return fp;
161 }
162
