Perl and epoch time question

Question

How can I take the current epoch time from perl and find the epoch time from 6 months ago?

I need to compare the create date of a file to see if it 6 months or older.

How is the difference between two numbers calculated? How can X seconds (or milliseconds, etc) be converted into days (or months)? (To be 100% accurate you'd need a Date module that understands leap-days and whatnot. However, for "6 months", basic math is A-OK.) — , Jun 29 '11 at 04:35
I just need a rough calculation, does not need nano seconds and what not. I just need to see if the file is older than 6 months, if it is we delete it. — AtomicPorkchop, Jun 29 '11 at 04:41
@pst: For "a week" or "N days", basic math is OK, but the number of days in six months varies depending on the start/end date. — Dave Sherohman, Jun 29 '11 at 09:24

score 4 · Answer 1 · answered Jun 29 '11 at 04:47

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The difference can be calculated using DateTime:

use DateTime;

my $dt = DateTime->now;  # or if you have epoch: DateTime->from_epoch( 'epoch' => $epoch );
$dt->subtract( DateTime::Duration->new( 'months' => 6 ) );

answered Jun 29 '11 at 04:47

Alan Haggai Alavi

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Oo I like that solution, do you happen to know if DateTime is a core module? – AtomicPorkchop Jun 29 '11 at 05:04
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_[Solignis](http://stackoverflow.com/users/386901/solignis)_: `DateTime` is not a core module. You can check if a module is in core using `corelist`. Example: `corelist DateTime`. – Alan Haggai Alavi Jun 29 '11 at 05:11
_[Solignis](http://stackoverflow.com/users/386901/solignis)_: You are welcome. :-) – Alan Haggai Alavi Jun 29 '11 at 06:51

score 1 · Answer 2 · answered Jun 29 '11 at 04:35

1

The Date::Calc package has functions for that. Use Date_to_Time and Time_to_Date to convert to/from epoch time, and use Add_Delta_YM to add -6 months.

answered Jun 29 '11 at 04:35

Ted Hopp

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Bah! I cannot get that module on Windows. – AtomicPorkchop Jun 29 '11 at 04:45
Depending on how much error you can tolerate, you can compute epoch time minus six months by subtracting (365 * 24 * 60 * 60 * 500) from now. (Those should probably be long values.) The 500 (instead of 1000) at the end is for half a year instead of a full year. This is likely to be off by a day or two. – Ted Hopp Jun 29 '11 at 05:01

score 0 · Answer 3 · answered Jun 29 '11 at 04:56

0

Rough and ready?

perl -le '$sixm = 30.5*6; for ( glob("*") ) { print "delete $_" if -M > $sixm }'

answered Jun 29 '11 at 04:56

Ashley

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Perl and epoch time question

3 Answers3