Replacing a “time” column with values in minutes since time "0" [closed] - perl

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I think it won't be a straightforward thing to solve, but here it is. I have a file in the following format:
"2004-04-19 12:25:00" 44 44
"2004-04-19 12:26:30" 36 36
"2004-04-19 12:27:15" 34 34
and I need a file with exact same content, except that the first row of the first column is 0, and remaining values of the first column are times in minutes since time 0 (since first time). Times should be rounded 3 digit after decimal (dot), like this:
0.000 44 44
1.500 36 36
2.250 34 34

Answer 1

I am as disappointed as the others who downvoted your question with your reluctance to even attempt to do this for yourself before asking for free help. If you always do this then you will never learn the language and will always have to rely on other people to do it for you. However, I would prefer that you got your solution from Stack Overflow, as I am sure you will only go elsewhere and ask the same question
This will do as you ask. It expects the path to the input file as a parameter on the command line, and sends the output to STDOUT
To write the output to a file you would redirect it on the command line, like this
$perl fractional_minutes.pl mydata.txt > mydata_new.txt
and if you want to write back to the same file then you will need to use Perl's in-place option, like this
$perl -i.bak fractional_minutes.pl mydata.txt
which will save the old file as mydata.txt.bak
use strict;
use warnings;
use Time::Piece;
use Time::Seconds qw/ ONE_MINUTE /;
my $t0;
while ( <> ) {
s{^"([^"]*)"}{
my $t = Time::Piece->strptime($1, '%Y-%m-%d %H:%M:%S');
$t0 = $t if not defined $t0;
sprintf('%.3f', ($t - $t0) / ONE_MINUTE);
}e;
print;
}
output
0.000 44 44
1.500 36 36
2.250 34 34

Answer 2

With GNU awk for mktime() and gensub():
$ cat tst.awk
BEGIN { FS="\"" }
{ mins=mktime(gensub(/[-:]/," ","g",$2)) / 60 }
NR==1 { startMins=mins }
{ printf "%.3f%s\n", (mins-startMins), $3 }
$ awk -f tst.awk file
0.000 44 44
1.500 36 36
2.250 34 34

Answer 3

Here is a solution that uses Time::Moment:
#!/usr/bin/perl
use strict;
use warnings;
use Time::Moment;
my #times = map {
Time::Moment->from_string($_ . 'Z', lenient => 1)
} ('2004-04-19 12:25:00',
'2004-04-19 12:26:30',
'2004-04-19 12:27:15');
my $first = $times[0];
foreach my $time (#times) {
printf "%.3f\n", ($time->rd - $first->rd) / (1/60/24);
}
Output:
0.000
1.500
2.250