Programming

Please do use tags, else it would be difficult to read your code.

Output that you get is logical.

"use CTRL \\ for exiting" ==> would be immediately printed once it encounters a "\n".
Yes, there is a "\n" in the printf, so its getting printed.

The next statement, "iiiiiiiiiiiiiis" now will be in the stdout buffer and would remain to be there, unless the buffer is full and the kernel explicitly flushes it out or there is a "\n" in the printf.

Neither of the conditions are satisfied here,
so when CTRL + \ is given to the running binary, the function 'suicide' is executed which prints the statement in the printf block and it has got a "\n".

So, the new statement - " hii u r in suicide ", is appended in the stdout buffer along with "iiiiiiiiiiiiiiiiis" and gets printed.

That counts as operating system dependent to me.

I always recommend sigaction to avoid ambiguity.

I perfectly agree with that !

I thought either of the semantics - old or new signal semantics is possible to be used in any of the flavors of unix/linux.

One more question, was that quote by 'Stevens' from some forum or was that from a book ?

If thats from forum - which forum is it from ?

From the Bible, "UNIX Network Programming" by the late W. Richard Stevens.