AT&T UNIX™PC Unix System V Users Manual - tenox

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SETBUF (3S) SETBUF (3S)
NAME setbuf - assign buffering to a stream
SYNOPSIS
#include
void setbuf (stream, buf)
FILE •stream;
char •buf;
int setvbuf (stream, buf, type, size)
FILE *stream;
char *buf;
int type, size;
DESCRIPTION
Setbuj is used after a stream has been opened but before it is read
or written. It causes the character array pointed to by buf to be
used instead of an automatically allocated buffer. If buf is a NULL
character pointer input/output will be completely unbuffered.
A constant BUFSIZ, defined in the header file, tells
how big an array is needed:
char buf[BUFSIZ] ;
Setbuf may be used after a stream has been opened but before it is
read or written. Type determines how stream will be buffered.
Legal values for type (defined in stdio.h) are:
_IOFBF causes input to be fully buffered.
_IOLBF causes output to be line buffered; the buffer will be
flushed when a new line is written, the buffer is full, or
input is requested.
JONBF causes input and output to be completely unbuffered.
A buffer is normally obtained from malloc(3C) at the time of the
first getc or putc(3S) on the file, except that the standard error
stream stderr is normally not buffered.
Output streams directed to terminals are always line-buffered
unless they are unbuffered.
SEE ALSO
fopen(3S), getc(3S), malloc(3C), putc(3S).
NOTE
A common source of error is allocating buffer space as an
"automatic" variable in a code block, and then failing to close the
stream in the same block.
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