All I'm saying is that ps on some systems invokes kernel mode code. I agree that spawning a process for this from C is a bad idea, but until the OP learns internals and systems calls he cannot get away from ps..

get the processid, and send signal-0 to that processid
if return value is equal to 0, process is available else its not available,

here there is no need to spawn a process with system call,

isn't this better ???

else,
if you dont accept what Jim said,

i believe you should read the kernal internal data structure- process table as such ... which is done by ps.

And the code should itself switch to kernal mode to become permissible to read the process table and its entries

not all ps implementations do so

Thanks, I'll try

i didnt mean it that way...

my intention was just to say.. read the kernel data structure - process table and its entries

the usage ps is just an example and not a standard

the unix programming faq contains sample programms for that. on linux it can be done by
searching /proc