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C built-in function for a Bash script

Bash script
now=`date "+%s"`
The above Bash script convert today 's date to a number.

1) Are the year, month, date, hour, minutes, seconds
and thousands of a second involved in this conversion ?

2) What is the mathematical formular for this conversion ?

3) What is the C built-in function for the above Bash
script ?

This is a 32 bit unsigned integer representing the number of seconds since what is called the epoch, January the 1st, 1970 UTC.

Re: C built-in function for a Bash script

Quote:

Originally posted by Linh
Bash script
now=`date "+%s"`
The above Bash script convert today 's date to a number.

1) Are the year, month, date, hour, minutes, seconds
and thousands of a second involved in this conversion ?

No, just seconds. But you can get the nanoseconds part of the time since the epoch with: date "+%N"
Or in C using the gettimeofday() function.

Quote:

2) What is the mathematical formular for this conversion ?

None actually. It's the other way around: The system (kernel) base format for the current time is in "number of seconds since the epoch". All other time formats are conversions from this.

Quote:

3) What is the C built-in function for the above Bash
script ?

That is the time() function. This example below does the same as: date "+%s".

Code:

#include <stdio.h>

#include <time.h>



int main()

{

        printf("%ld\n", (long int)time(NULL));

        return 0;

}

jlliagre, and Hko. Thank you both for your help.