setbuf(3S)setbuf(3S)NAMEsetbuf(), setvbuf(), setlinebuf() - assign buffering to a stream file
SYNOPSIS
Obsolescent Interface
DESCRIPTION
can be used after a stream has been opened but before it is read or
written. It causes the array pointed to by buf to be used instead of
an automatically allocated buffer. If buf is the NULL pointer
input/output will be completely unbuffered.
A constant defined in the header file, tells how big an array is
needed:
can be used after a stream has been opened but before it is read or
written. type determines how stream is to be buffered. Legal values
for type (defined in are:
causes input/output to be fully buffered.
causes output to be line buffered;
the buffer will be flushed when a newline is writ‐
ten, the buffer is full, or input is requested.
causes input/output to be completely unbuffered.
When an output stream is unbuffered, information is queued for writing
on the destination file or terminal as soon as written; when it is
buffered, many characters are saved up and written as a block. When
the output stream is line-buffered, each line of output is queued for
writing on the destination terminal as soon as the line is completed
(that is, as soon as a new-line character is written or terminal input
is requested). can also be used to explicitly write the buffer.
If buf is not the NULL pointer, the array it points to is used for
buffering instead of an automatically allocated buffer (from size spec‐
ifies the size of the buffer to be used. The constant in is suggested
as a good buffer size. If input/output is unbuffered, buf and size are
ignored.
By default, output to a terminal is line buffered and all other
input/output is fully buffered.
is used to change stream from block-buffered or unbuffered to line-
buffered. can be used any time the file descriptor is active.
Obsolescent Interface
assigns buffering to a stream file.
DIAGNOSTICS
If an illegal value for type or size is provided, return a non-zero
value. Otherwise, the value returned will be zero.
Note
A common source of error is allocating buffer space as an "automatic"
variable in a code block, then failing to close the stream in the same
block.
Allocating a buffer of size or bytes does not necessarily imply that
all of size or bytes are used for the buffer area.
AUTHOR
and were developed by HP.
SEE ALSOflockfile(3S), fopen(3S), getc(3S), malloc(3C), putc(3S), stdio(3S),
thread_safety(5), glossary(9).
STANDARDS CONFORMANCEsetbuf(3S)
