Syntax

#include <stdio.h>
void setbuf(FILE *stream, char *buffer);

setbuf controls buffering for the specified stream. The stream pointer must refer to an open file before any I/O or repositioning has been done.

If the buffer argument is NULL, the stream is unbuffered. If not, the buffer must point to a character array of length BUFSIZ, which is the buffer size defined in the <stdio.h> include file. The system uses the buffer, which you specify, for input/output buffering instead of the default system-allocated buffer for the given stream.

setvbuf is more flexible than setbuf.

Note: Streams are fully buffered by default, with the exceptions of stderr, which is line-buffered, and memory files, which are unbuffered.

There is no return value.

This example opens the file setbuf.dat for writing. It then calls setbuf to establish a buffer of length BUFSIZ. When string is written to the stream, the buffer buf is used and contains the string before it is flushed to the file.

#include <stdio.h>

#define FILENAME  "setbuf.dat"

int main(void)
{
   char buf[BUFSIZ];
   char string[] = "hello world";
   FILE *stream;

   memset(buf, '\0', BUFSIZ);           /* initialize buf to null characters  */
   stream = fopen(FILENAME, "wb");
   setbuf(stream, buf);                                   /* set up buffer    */
   fwrite(string, sizeof(string), 1, stream);
   printf("%s\n", buf);                   /* string is found in buf now       */
   fclose(stream);                  /* buffer is flushed out to output stream */
   return 0;

   /****************************************************************************
      The output file should contain:

      hello world

      The output should be:

      hello world
   ****************************************************************************/
}

• fclose
  
• fflush
  
• flushall
  
• fopen
  
• setvbuf

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