In Perl, localtime takes a Unix timestamp and gives back year/month/day/hour/min/sec etc. I'm looking for the opposite of localtime: I have the parts, and I'd like to build a unix timestamp from them.
You can use the timelocal function in the Time::Local CPAN module.
NAME
Time::Local - efficiently compute time
from local and GMT time
SYNOPSIS
$time = timelocal($sec,$min,$hour,$mday,$mon,$year);
$time = timegm($sec,$min,$hour,$mday,$mon,$year);
DESCRIPTION
This module provides functions that
are the inverse of built-in perl
functions localtime() and gmtime().
They accept a date as a six-element
array, and return the corresponding
time(2) value in seconds since the
system epoch (Midnight, January 1,
1970 GMT on Unix, for example). This
value can be positive or negative,
though POSIX only requires support for
positive values, so dates before the
system's epoch may not work on all
operating systems.
It is worth drawing particular
attention to the expected ranges for
the values provided. The value for the
day of the month is the actual day (ie
1..31), while the month is the number of months since January (0..11). This
is consistent with the values returned
from localtime() and gmtime().
Note: POSIX::mktime is a just a wrapper around your C library's mktime() function. Time::Local is a pure-Perl implementation, and always returns results matching Perl's localtime. Also, Time::Local offers gmtime, while mktime only works in local time. (Well, you could try changing $ENV{TZ}, but that doesn't work on some systems.)
POSIX::mktime
DateTime on CPAN might of of some use. It also has a lot of time manipulation/translation methods.
Just create the DateTime using your parts and call $datetime->formatter("%s") ;
Related
I am looking to convert timestamps such as the following
2019-01-01T02:15:00+00:00
Into Australian Eastern Standard Time in Perl.
I have over 10,000 of these timestamps, any help would be really appreciated
I need to input them into a mysql DB with a format of YYYY-MM-DD hh:mm:ss
You would use the standard Perl module Time::Piece. It provides the standard strptime and strftime functions. The first allows you to parse a timestamp with a template and the second outputs a timestamp based on the same kind of template. To change timezones you would add or subtract the number of seconds difference.
$t = Time::Piece->strptime("2020-11-04T01:46:00", "%Y-%m-%dT%H:%M:%S");
$t += $offset;
print $t->strftime("%Y-%m-%dT%H:%M:%S");
Or if your current time is the current locale and you're always converting from GMT:
$t = Time::Piece->strptime("2020-11-04T01:46:00", "%Y-%m-%dT%H:%M:%S");
$l = localtime $t->epoch;
print $l->strftime("%Y-%m-%dT%H:%M:%S");
Now if you need to do something more complicated than that (daylight savings time, leap seconds), there is the DateTime module but it is correspondingly far more complicated to use.
See also How can I parse dates and convert time zones in Perl?
HTH
Executing a simple Perl script
use Time::Piece;
my $t = Time::Piece->strptime('08:00 PM AST', "%I:%M %p %Z");
I got the following error: Error parsing time at /usr/local/lib/perl5/Time/Piece.pm line 469.
Is this a bug in the library or there is something wrong with the above code? When I remove AST time-zone from the input string, it works, but when time-zone is left, it fails.
I don't know what exact time-zone will be in input string, so I cannot adjust that part on my end. AST (see Wikipedia) is a proper abbreviation for Atlantic Time Zone, so it should work. But it does not!
The time zone field is ambiguous and cannot be parsed. For instance, CST is the abbreviation for China Standard Time, Central Standard Time, and Cuba Standard Time.
The module documentation says that the strptime method is from FreeBSD, where the %Z format accepts either the local time zone or GMT and nothing else. This may be true of strptime, but I can confirm only that, where I am located, GMT is acceptable while UTC and AST are not.
The solution I would recommend is to preprocess your time strings, replacing the time zone abbreviation with an unambiguous time zone offset. For instance AST (assuming you meant Atlantic Standard Time and not Arabia Standard Time) would be replaced with -0400, since it is four hours behind UTC. Then you can parse it with a %z format specifier and get the correct result.
use Date::Parse;
my $t = str2time('08:00 PM AST');
perl code:
#!/bin/env perl
use DateTime;
print DateTime->now;
OUTPUT:
2013-01-28T06:02:33
what's mean of 'T' letter in the output string ?
ISO8601 and RFC3339 both use "T" to join the date and the time, and DateTime's default stringifier apparently adopted that convention. If you want another format, you can use one of the DateTime::Format::* modules or ->strftime.
my $now = DateTime->now( time_zone => 'local' );
say $now->strftime('%Y-%m-%d %H:%M:%S');
It stands for "Time". You can read more at:
http://en.wikipedia.org/wiki/ISO_8601#Combined_date_and_time_representations
It's the separator between date and time in ISO 8601. It's always a T in this format.
The character [T] shall be used as time designator to indicate the start of the representation of the time of day
component in these expressions. The hyphen [-] and the colon [:] shall be used, in accordance with 4.4.4, as
separators within the date and time of day expressions, respectively, when required.
NOTE By mutual agreement of the partners in information interchange, the character [T] may be omitted in
applications where there is no risk of confusing a date and time of day representation with others defined in this
International Standard.
--Data elements and interchange
formats — Information interchange —
Representation of dates and times, ISO 8601:2004(E)
How can I determine the current date and time of various countries using a PERL script that executes on a server in the US? For example, getDTnow() should determine the current date and time on the server and use that to return the date and time of various countries.
P.S: It would be great if this can be done using only the built-in functions, without any external modules.
Conclusion: Date maths is [use swear word here] complicated and easy to get wrong. Other perl gurus on IRC, groups and other parts of the net confirmed what Ether had been advicing me - use DateTime. DVK's solution is also pretty neat for those of you who don't mind messing with the perl environment. (Note: Though on windows, the caveats section of the Time::Piece docs says one should be careful while 'Setting $ENV{TZ} in Threads on Win32').
DateTime is a wonderful library that can use standard timezones to do everything you desire and more:
use DateTime;
# returns local time in Italy
my $dt = DateTime->now(time_zone => 'Europe/Rome');
# prints time in desired format
print "The current date and time in Italy is: ", $dt->strftime('%Y-%m-%d %T');
You can control which timezone localtime returns in via TZ environmental variable:
local $ENV{TZ} = ":/usr/share/lib/zoneinfo/Asia/Tokyo";
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday) = localtime();
print "$sec,$min,$hour,$mday,$mon,$year,$wday,$yday\n"'
# Prints 40,58,4,12,0,111,3,11
local $ENV{TZ} = ":/usr/share/lib/zoneinfo/Europe/London";
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday) = localtime();
print "$sec,$min,$hour,$mday,$mon,$year,$wday,$yday\n"'
# Prints 41,58,19,11,0,111,2,10
Unfortunately, the path above is different on different Unixes (/usr/share/lib/zoneinfo on Solaris, /usr/share/zoneinfo on Linux). Since there appear to be no other variations, a slightly portable version would check which of the 2 directories exists and use that - but this obviously only works on Solaris and Linux and may be other unixes. No idea about Windows/MacOS/whatnot.
Valid locations for TZ can be found here: http://www.timezoneconverter.com/cgi-bin/tzref.tzc (but not all of them would necessarily be available on your system - check the above directory).
Please see http://en.wikipedia.org/wiki/Tz_database for more info on TZ database.
You could always store the variation from your timezone in a hash where the key is the timezone and the value is the adjustment from the current time. then when you pass the current time it should return the local time for that zone.
I extracted year, month, day, hour, minute, second, and millisecond data from human readable text (it wasn't in a timestamp format, but rather something like "X started at HH:MM:SS.SSS on DD MMM YYYY and ended at HH:MM:SS.SSSS on DD MMM YYYY"), so for each recorded event, I have each of the values.
However, I need to turn those into some kind of timestamp so I can do math on it - I want to determine how long the event lasted (end time - start time). I was hoping the time function would take parameters so I can create two arbitrary times, but that doesn't appear to be the case.
If possible, I would like to stick with functions available in the core Perl libraries or scripts that I can add to the project, since getting CPAN modules installed on the target machines would just make a headache for everyone, if it is even possible to get the modules through the security restrictions.
You want the CPAN module DateTime. Here's an introduction.
On a Debian GNU/Linux or Ubuntu system, simply run:
apt-get install libdatetime-perl
to install the module.
You can do it with Time:Local. It's basically the reverse of the built in "localtime" function, so you can generate a timestamp from a standard date.
In terms of built-ins these may be helpful:
POSIX (for mktime and strftime)
Time::Piece, Time::Local and Time::Seconds. These are all standard in Perl 5.10, but may not be available by default on earlier systems.
That said, time/date calculations are complex. If the only obstacle is a few headaches installing modules (rather than a company policy forbidding them), I would really recommend looking at CPAN.
Edit: I see from your comment on another post that there are company restrictions. You should update your original post, since there's a big difference between "headaches" and "security restrictions." In any case, DateTime and Date::Manip are worth looking at. Even if you don't install them, you can get a lot out of reading their source.
If you were only interested in comparing times,
my $ts1 = sprintf( '%4.4d%2.2d%2.2d%2.2d%2.2d%3.3d',
$year1, $month1, $mday1, $hour1, $min1, $sec1, $ms1 );
to
my $ts2 = sprintf( '%4.4d%2.2d%2.2d%2.2d%2.2d%3.3d',
$year2, $month2, $mday2, $hour2, $min2, $sec2, $ms2 );
using cmp would be sufficient.
To do arithmetic on these times, use Time::Local to get seconds since epoch and then add the $ms1/1000 to that value.
my $time1 = timelocal($sec1, $min1, $hour1, $mday1, $mon1, $year1) + $ms1/1000;
You can use POSIX::mktime to turn broken-up time into a timestamp. Be aware that the month is 0-based, and the year is 1900-based, so adjust accordingly. :-)
use POSIX qw(mktime);
$timestamp = mktime($sec, $min, $hour, $day, $month - 1, $year - 1900);