setvbuf

int setvbuf ( FILE * stream, char * buffer, int mode, size_t size );

Change stream buffering

Parameters

stream

Pointer to a FILE object that identifies an open stream.

buffer

User allocated buffer. Must be at least size bytes long.
If set to NULL, the function automatically allocates a buffer of the specified size.

mode

Specifies a mode for file buffering:

_IOFBF	Full buffering: On output, data is written once the buffer is full. On Input the buffer is filled when an input operation is requested and the buffer is empty.
_IOLBF	Line buffering: On output, data is written when a newline character is inserted into the stream or when the buffer is full, whatever happens first. On Input, the buffer is filled up to the next newline character when an input operation is requested and the buffer is empty.
_IONBF	No buffering: No buffer is used. Each I/O operation is written as soon as possible. In this case, the buffer and size parameters are ignored.

size

Buffer size in bytes.
If the buffer argument is NULL, this determines the minimum size automatically allocated by the function for the buffer, otherwise it must be a value equal or lower to the size in bytes of the array specified as buffer.

Return Value

Example

/* setvbuf example */
#include <stdio.h>
int main ()
{
  FILE *pFile;
  pFile=fopen ("myfile.txt","w");
  setvbuf ( pFile , NULL , _IOFBF , 1024 );
  // File operations here
  fclose (pFile);
  return 0;
}

See also