setvbuf

associate a buffer with a file

Synopsis:

#include <stdio.h>
int setvbuf( FILE *fp,
             char *buf,
             int mode,
             size_t size );

Description:

The setvbuf() function can be used to associate a buffer with the file designated by fp. If this function is used, it must be called after the file has been opened, and before it has been read or written. The argument mode determines how the file fp will be buffered, as follows:

_IOFBF

causes input/output to be fully buffered.

_IOLBF

causes output to be line buffered (the buffer will be flushed when a new-line character is written, when the buffer is full, or when input is requested.

_IONBF

causes input/output to be completely unbuffered.

If the argument buf is not NULL, the array to which it points will be used instead of an automatically allocated buffer. The argument size specifies the size of the array.

Returns:

The setvbuf() function returns zero on success, or a non-zero value if an invalid value is given for mode or size.

See also:

fopen(), setbuf()

Examples:

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

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

  fp = fopen( "file", "r" );
  buf = malloc( 1024 );
  setvbuf( fp, buf, _IOFBF, 1024 );
}

Classification:

ANSI

Systems:

All (except DOS/PM)