1 .\" Copyright (c) 1980, 1991 Regents of the University of California.
2 .\" All rights reserved.
4 .\" This code is derived from software contributed to Berkeley by
5 .\" the American National Standards Committee X3, on Information
6 .\" Processing Systems.
8 .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB)
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19 .\" This product includes software developed by the University of
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21 .\" 4. Neither the name of the University nor the names of its contributors
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38 .\" @(#)setbuf.3 6.10 (Berkeley) 6/29/91
40 .\" Converted for Linux, Mon Nov 29 14:55:24 1993, faith@cs.unc.edu
41 .\" Added section to BUGS, Sun Mar 12 22:28:33 MET 1995,
42 .\" Thomas.Koenig@ciw.uni-karlsruhe.de
43 .\" Correction, Sun, 11 Apr 1999 15:55:18,
44 .\" Martin Vicente <martin@netadmin.dgac.fr>
45 .\" Correction, 2000-03-03, Andreas Jaeger <aj@suse.de>
46 .\" Added return value for setvbuf, aeb,
48 .TH SETBUF 3 2016-03-15 "Linux" "Linux Programmer's Manual"
50 setbuf, setbuffer, setlinebuf, setvbuf \- stream buffering operations
55 .BI "void setbuf(FILE *" stream ", char *" buf );
57 .BI "void setbuffer(FILE *" stream ", char *" buf ", size_t " size );
59 .BI "void setlinebuf(FILE *" stream );
61 .BI "int setvbuf(FILE *" stream ", char *" buf ", int " mode \
66 Feature Test Macro Requirements for glibc (see
67 .BR feature_test_macros (7)):
74 Glibc 2.19 and earlier:
77 The three types of buffering available are unbuffered, block buffered, and
79 When an output stream is unbuffered, information appears on
80 the destination file or terminal as soon as written; when it is block
81 buffered many characters are saved up and written as a block; when it is
82 line buffered characters are saved up until a newline is output or input is
83 read from any stream attached to a terminal device (typically \fIstdin\fP).
86 may be used to force the block out early.
90 Normally all files are block buffered.
91 If a stream refers to a terminal (as
93 normally does), it is line buffered.
94 The standard error stream
96 is always unbuffered by default.
100 function may be used on any open stream to change its buffer.
103 argument must be one of the following three macros:
116 Except for unbuffered files, the
118 argument should point to a buffer at least
120 bytes long; this buffer will be used instead of the current buffer.
124 only the mode is affected; a new buffer will be allocated on the next read
128 function may be used only after opening a stream and before any other
129 operations have been performed on it.
131 The other three calls are, in effect, simply aliases for calls to
135 function is exactly equivalent to the call
138 setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
143 function is the same, except that the size of the buffer is up to the
144 caller, rather than being determined by the default
148 function is exactly equivalent to the call:
151 setvbuf(stream, NULL, _IOLBF, 0);
156 returns 0 on success.
157 It returns nonzero on failure
159 is invalid or the request cannot be honored).
164 The other functions do not return a value.
166 For an explanation of the terms used in this section, see
172 Interface Attribute Value
179 T} Thread safety MT-Safe
186 functions conform to C89 and C99.
191 .\" .BR setlinebuf ()
192 .\" functions are not portable to versions of BSD before 4.2BSD, and
193 .\" are available under Linux since libc 4.5.21.
194 .\" On 4.2BSD and 4.3BSD systems,
196 .\" always uses a suboptimal buffer size and should be avoided.
198 You must make sure that the space that
200 points to still exists by the time
202 is closed, which also happens at program termination.
203 For example, the following is invalid:
213 printf("Hello, world!\\n");