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32 .\" @(#)fopen.3 8.1 (Berkeley) 6/4/93
33 .\" $FreeBSD: src/lib/libc/stdio/fopen.3,v 1.20 2007/01/09 00:28:06 imp Exp $
42 .Nd stream open functions
48 .Fn fopen "const char * restrict path" "const char * restrict mode"
50 .Fn fdopen "int fildes" "const char *mode"
52 .Fn freopen "const char * restrict path" "const char * restrict mode" "FILE * restrict stream"
57 opens the file whose name is the string pointed to by
59 and associates a stream with it.
63 points to a string beginning with one of the following
64 sequences (Additional characters may follow these sequences.):
65 .Bl -tag -width indent
67 Open file for reading.
68 The stream is positioned at the beginning of the file.
70 Open file for writing.
71 Creates the file if it does not already exist,
72 truncates the file if it does.
75 Creates the file if it does not already exist.
76 Seeks to end of the file.
77 Subsequent writes to the file will always end up at the then current
78 end of file, irrespective of any intervening
83 Additional flags may modify the primary mode as follows:
84 .Bl -tag -width indent
86 The file will be opened for both reading and writing.
87 For example 'r+' or 'w+'.
89 The open will fail if the file already exists (C11).
93 The underlying descriptor will automatically be closed on any
95 (glibc compatibility).
98 On UNIX systems file reading and writing is always in binary
99 mode so this flag has no effect.
104 string can also include the letter ``b'' either as a third character or
105 as a character between the characters in any of the two-character strings
107 This is strictly for compatibility with
109 and has no effect; the ``b'' is ignored.
111 Any created files will have mode
124 as modified by the process'
128 Reads and writes may be intermixed on read/write streams in any order,
129 and do not require an intermediate seek as in previous versions of
131 This is not portable to other systems, however;
134 a file positioning function intervene between output and input, unless
135 an input operation encounters end-of-file.
139 function associates a stream with the existing file descriptor,
142 of the stream must be compatible with the mode of the file descriptor.
143 When the stream is closed via
151 opens the file whose name is the string pointed to by
153 and associates the stream pointed to by
156 The original stream (if it exists) is closed.
159 argument is used just as in the
168 attempts to re-open the file associated with
171 The new mode must be compatible with the mode that the stream was originally
173 .Bl -bullet -offset indent
175 Streams originally opened with mode
177 can only be reopened with that same mode.
179 Streams originally opened with mode
181 can be reopened with the same mode, or mode
184 Streams originally opened with mode
186 can be reopened with the same mode, or mode
189 Streams originally opened with mode
194 can be reopened with any mode.
197 The primary use of the
200 is to change the file associated with a
202 .Dv ( stderr , stdin ,
206 Upon successful completion
216 is returned and the global variable
218 is set to indicate the error.
239 may also fail and set
241 for any of the errors specified for the routine
247 may also fail and set
249 for any of the errors specified for the routine
255 may also fail and set
257 for any of the errors specified for the routine
263 may also fail and set
265 for any of the errors specified for the routines