Here it goes...
CLOCK
Syntax
#include <time.h>
clock_t clock(void);
Description
This function returns the number of clock ticks since an arbitrary time, actually, since the first call to clock, which itself returns zero. The number of tics per second is CLOCKS_PER_SEC.
Return Value
The number of tics.
Portability
ANSI, POSIX
Example
printf("%d seconds have elapsed\n", clock()/CLOCKS_PER_SEC);
SLEEP
Syntax
#include <unistd.h>
unsigned sleep(unsigned seconds);
Description
This function causes the program to pause for seconds seconds.
Return Value
The number of seconds that haven't passed (i.e. always zero)
Portability
not ANSI, POSIX
Example
sleep(5);