Hi all, I am writing user- space driver. My intention is to print whatever string i am enter into terminal. Here i am using setbuf function to sent the data to the print after some fixed string length. I wrote below program for understand setbuf functionality. But i am getting unpredictable result for some output . can any one explain the why i am getting these result. root@desktop:/home/prabhu# cat a.c #include <stdio.h> main() { char buff2[]= "hello world"; char buf1[6]=""; setbuf(stdin, buf1); getchar(); printf ("%s",buf1); } root@desktop:/home/prabhu# cc a.c root@desktop:/home/prabhu# ./a.out a a root@desktop:/home/prabhu# ./a.out aa aa root@desktop:/home/prabhu# ./a.out aaa aaa root@desktop:/home/prabhu# ./a.out aaaa aaaa root@desktop:/home/prabhu# ./a.out aaaaa aaaaa hello worldroot@desktop:/home/prabhu# ./a.out aaaaaa aaaaaa ello worldroot@desktop:/home/prabhu# ./a.out aaaaaaa aaaaaaa llo worldroot@desktop:/home/prabhu# ./a.out aaaaaaaa aaaaaaaa lo worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaa aaaaaaaaa o worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaaa aaaaaaaaaa worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaaaa aaaaaaaaaaa Thanks, Prabhu