Format
#include <stdio.h>
void setbuf(FILE *, char *buffer);Language Level: ANSI
Threadsafe: Yes.
Description
If the operating system supports user-defined buffers, setbuf() controls buffering for the specified stream. The setbuf() function only works in ILE C when using the integrated file system. 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 that is 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. stdout, stderr, and stdin do not support user-defined buffers.
The setvbuf() function is more flexible than the setbuf() function.
Return Value
There is no return value.
Example that uses setbuf()
This example opens the file setbuf.dat for writing. It then calls the setbuf() function 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>
int main(void)
{
char buf[BUFSIZ];
char string[] = "hello world";
FILE *stream;
memset(buf,'\0',BUFSIZ); /* initialize buf to null characters */
stream = fopen("setbuf.dat", "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 myfile.dat */
}Related Information