NAME

setbuf, setvbuf – assign buffering to a stream

SYNOPSIS

#include <stdio.h>

void setbuf( FILE *stream, char *buf );

void setvbuf( FILE *stream, char *buf, int type, size_t size);

DESCRIPTION

setvbuf() may 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. The argument type determines how stream shall be buffered, as follows:

• {_IOFBF} shall cause input/output to be fully buffered.
• {_IOLBF} shall cause input/output to be line buffered.
• {_IONBF} shall cause input/output to be unbuffered.

Currently setvbuf() supports only _IOFBF mode.
The size of the buffer may be not less than constant BUFSIZ, defined in the <stdio.h> header. It is typically a good buffer size.

setbuf() equivalent to:
setvbuf(stream, buf, _IOFBF, BUFSIZ) – if buf is not a null pointer
or to:
setvbuf(stream, buf, _IONBF, BUFSIZ) – if buf is a null pointer.

RETURN VALUES

Upon successful completion, setvbuf() shall return 0. Otherwise, it shall return a non-zero value and set errno to indicate the error.
The setbuf() function does not return a value.

ERRORS

The setvbuf function fails if:

[ENOTSUP]

Buffer size size is less than BUFSIZ, or type is not equal to _IOFBF.

SEE ALSO

fopen(), getc(), malloc(), putc()

NOTES

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.