Question

I have a requirement to start my application at certain time. I don’t want to be put in the corn job. My executable is an application and like to start on 2011-Jan-20
So I have to run it as
./app –date 2011-Jan-20

Here problem is, how I will calculates the time difference from current and date supplied in command line option.

I don’t want to write won function. Is there any in build function are available for such type of time difference. ( c and Linux)

Answer 1

You can calculate the difference between the start time and now in milliseconds and then wait for that many milliseconds by passing that number as a timeout argument to select() or epoll().

To calculate the difference, one way is to first convert your date string to struct tm using strptime() and then pass it to mktime() which is going to give you a number of seconds since unix epoch 1970-01-01 00:00:00. Then get the current time by using gettimeofday() or clock_gettime(), they also report time passed since unix epoch. Convert the start time and the current time to seconds and subtract the values.