setbuf()

Associate a buffer with a stream

Synopsis:

#include <stdio.h>

void setbuf( FILE *fp, 
             char *buffer );

Arguments:

fp: The stream that you want to associate with a buffer.
buffer: NULL, or a pointer to the buffer; see below.

Library:

libc

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

Description:

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

If buffer is NULL, all input/output for the stream is completely unbuffered. If buffer isn't NULL, then it must point to an array that's at least BUFSIZ characters long, and all input/output is fully buffered.

Note:

The setbuf() function doesn't have a way to notify you if an error occurred; you should use setvbuf() instead.
(QNX Neutrino 6.6 or later) As a QNX Neutrino extension, you can use the STDIO_DEFAULT_BUFSIZE environment variable to override BUFSIZ as the default buffer size for stream I/O. The value of STDIO_DEFAULT_BUFSIZE must be greater than that of BUFSIZ. For more information, see “Adjusting the buffer size” in the entry for fopen().

Examples:

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

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

    buffer = (char *)malloc( BUFSIZ );
    if( buffer == NULL ) {
        return EXIT_FAILURE;
    }

    fp = fopen( "some_file", "r" );

    setbuf( fp, buffer );

    /* . */
    /* . */
    /* . */

    fclose( fp );

    free( buffer );

    return EXIT_SUCCESS;
}

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	Yes