{{keywords>wiki library source code example reference}}
====== setvbuf ======
<code c>
    int setvbuf(FILE *stream, char *buffer, int mode, size_t size); 
</code>
Controls buffering for stream stream. mode is _IOFBF for full buffering, _IOLBF for line buffering, _IONBF for no buffering. Non-null buf specifies buffer of size size to be used; otherwise, a buffer is allocated. Returns non-zero on error. Call must be before any other operation on stream.
<code c>
    _IOLBF   File will buffered line by line
    _IONBF   Input/Output will not be buffered
    _IOFBF   Input/Output will fully buffered
</code>

===== C Sourcecode Example =====
<code c>
/* 
 * setvbuf example code
 * http://code-reference.com/c/stdio.h/setvbuf
 */

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */


int main ( void )
{
  FILE *stream_not_buffered, *stream_full_buffered, *stream_line_buffered;
  stream_full_buffered=fopen ("test.txt","w");
  stream_not_buffered=fopen("test2.txt","w");
  stream_line_buffered=fopen("test3.txt","w");
  
/* case 1 full buffered */
  setvbuf ( stream_full_buffered , NULL , _IOFBF , 2000L );

  fputs("Buffered input for setvbuf full buffered", stream_full_buffered);
  fflush(stream_full_buffered);
  fclose(stream_full_buffered);


/* case 2 not buffered */
  setvbuf ( stream_not_buffered , NULL , _IONBF , BUFSIZ );

  fputs("input for setvbuf not buffered", stream_not_buffered);
  fflush(stream_not_buffered);
  fclose(stream_not_buffered);


/* case 3 line buffered */
  setvbuf ( stream_line_buffered , NULL , _IOLBF , 80 );

  fputs("Buffered input for setvbuf line buffered", stream_line_buffered);
  fflush(stream_line_buffered);
  fclose(stream_line_buffered);


  return 0;
}

</code>


    output: ./setvbuf
    
==== content of test.txt ===
<code c>
Buffered input for setvbuf full buffered
</code>
==== content of test2.txt ===
<code c>
input for setvbuf not buffered
</code>
==== content of test3.txt ===
<code c>
Buffered input for setvbuf line buffered
</code>


see also  [[c:stdio.h:setbuf|]]