perl to open csv file with dynamic date in it? - perl

Question

How can I open a CSV file with a date that changes each day, where the date format is yyyy for year, dd for day and mmm for a 3 letter month.
This is as far as I've got
#!/usr/bin/perl
use strict;
use warnings;
#Set-up Input Files
#Inputfile
$INFILE = "C:\\DBR_%yyyy\\%b\\Failures_input%d%h\\.csv";
#Open input file for reading
open (INPUT,"$INFILE") or die " cannot open $INFILE ";

Answer 1

It is very unclear what you are asking for, and you don't mention %d and %h in your pattern.
If you want to open the latest CSV file then you need to do a nested search of the path, finding the latest date and time.
Here is something that may help. This code generates the path to the file that would be created for the current date and time. It uses the Time::Piece module, which is part of core Perl and shouldn't need installing. By default it overloads the localtime operator so that it returns a Time::Piece object in scalar context. That allows the module's utility methods to be applied directly.
use strict;
use warnings;
use Time::Piece;
my $failures_file = localtime->strftime('C:\DBR_%Y\%b\Failures_input%d%b.csv');
my $invoices_file = localtime->strftime('C:\%Y\%b\invoices%d%b.csv');
print $failures_file, "\n";
print $invoices_file, "\n";
output
C:\DBR_2014\Mar\Failures_input17Mar.csv
C:\2014\Mar\invoices17Mar.csv
However I think it is more likely that you want the name of the latest file with a path of that form, which is a little more complex (and a dreadful system design). Please verify your requirement and we will be able to help you further.

Answer 2

I wanted to write an answer about the localtime Perl function, but its documentation is so complete that it even includes stuff about the three-letter abbreviations.
A few remarks on your string literal for the filename:
You can use single forward slashes, even on Windows
You don't have to escape the dot with a backslash
You can "interpolate" variables into strings: "DBR_$yyyy" if $yyyy is a variable.

Answer 3

I second SzG's general recommendations.
The following shows how to add the date formatting to your filename using two core modules.
Using Time::Piece (in Perl core since version 5.8):
use Time::Piece;
use strict;
use warnings;
my $infile = localtime->strftime('C:\DBR_%Y\%b\Failures_input%d.csv');
Or using POSIX and strftime if you're working on an ancient box. To find the available specifiers, just google strftime:
use POSIX qw(strftime);
use strict;
use warnings;
my $infile = strftime 'C:\DBR_%Y\%b\Failures_input%d.csv', localtime;
Outputs:
C:\DBR_2014\Mar\Failures_input16.csv