Sets the internal buffer to use for stream operations. It should be at leastBUFSIZ characters long.

Ifbuffer is not null, equivalent tosetvbuf(stream, buffer,_IOFBF,BUFSIZ).

Ifbuffer is null, equivalent tosetvbuf(stream,NULL,_IONBF,0), which turns off buffering.

[edit]Parameters

[edit]Return value

None.

[edit]Notes

IfBUFSIZ is not the appropriate buffer size,setvbuf can be used to change it.

setvbuf should also be used to detect errors, sincesetbuf does not indicate success or failure.

This function may only be used afterstream has been associated with an open file, but before any other operation (other than a failed call tosetbuf/setvbuf).

A common error is setting the buffer of stdin or stdout to an array whose lifetime ends before the program terminates:

int main(void){char buf[BUFSIZ];    setbuf(stdin, buf);}// lifetime of buf ends, undefined behavior

[edit]Example

#include <stdio.h>#include <threads.h> int main(void){    setbuf(stdout,NULL);// unbuffered stdoutputchar('a');// 'a' appears immediately if stdout is unbufferedthrd_sleep(&(struct timespec){.tv_sec=1},NULL);// sleep 1 secputchar('b');}

ab

[edit]References

[edit]See also

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