setvbuf()

Arguments:

fp

The stream that you want to associate with a buffer.

buffer

NULL, or a pointer to the buffer; see below.

mode

How you want the stream to be buffered:

• _IOFBF — input and output are fully buffered.
• _IOLBF — output is line-buffered; that is, the buffer is flushed when a newline character is written, when the buffer is full, or when input is requested
  Note:

  When input is requested, the buffer is flushed only if it references a special file, such as a tty device.
• _IONBF — input and output are completely unbuffered.

size

The size of the buffer.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The setvbuf() function associates a buffer with the stream designated by fp. If you want to call setvbuf(), you must call it after opening the stream, but before doing any reading, writing, or seeking.

If buf isn't NULL, the buffer it points to is used instead of an automatically allocated buffer.

Returns:

0

Success.

EINVAL

The mode argument isn't valid.

ENOMEM

The buf argument is NULL, size isn't 0, and there isn't enough memory available to allocate a buffer.

Examples:

#include <stdio.h>
#include <stdlib.h>

int main( void )
{
    char *buf;
    FILE *fp;

    fp = fopen( "file", "r" );
    buf = malloc( 1024 );
    setvbuf( fp, buf, _IOFBF, 1024 );
    
    /* work with fp */
    ...
    
    fclose( fp );

    /* This is OUR buffer, so we have
     * to free it.  Do that AFTER
     * you've closed the file.
     */

    free( buf );
    return EXIT_SUCCESS;
}

Classification:

ANSI, POSIX 1003.1