Perl and text

This is, of course, where Perl really shines. I’m including some information on command line options, see perldoc perlrun for more details, and a handful of other packages to read/write common representations of data.

command line

split lines automatically on white-space

Splitting text on the command line with -a creates @F automatically, which has all of the processed text. It must be used with either the -n or -p options, which both place a loop around your script. The difference being that -p executes your commands and prints the value of $_ afterward.

perl -nalE '{ print $F[3]; }' some_file

specify how to split each line with `-F`

Specifying -F implicitly sets -a and -n. To split using the semicolon try:

perl -F';' -lE '{ print $F[2]; }' some_file

read csv

use Text::CSV_XS;
use Text::Iconv;
my $csv_reader = Text::CSV_XS->new({auto_diag => 1, binary => 1});

write csv

use Text::CSV_XS;
use Text::Iconv;
my $csv_writer = Text::CSV_XS->new({
  binary => 1, auto_diag => 1, always_quote => 1, eol => "\n"
});

read xls

use Spreadsheet::ParseExcel;
my $parser   = Spreadsheet::ParseExcel->new();
my $workbook = $parser->parse($file);

read xlsx

use Spreadsheet::XLSX;
use Text::Iconv;
my $converter = Text::Iconv->new("utf-8", "windows-1251");
my $in_excel = Spreadsheet::XLSX->new($file, $converter);

write xlsx

use Excel::Writer::XLSX;
my $workbook = Excel::Writer::XLSX->new("$out_ext.xlsx");
$workbook->set_properties(
  title    => "data created by $prog_name on $now_time",
  author   => 'TS Wingo',
  comments => 'created with perl and Excel::Writer::XLSX'
);

Perl and seralizing data

JSON - for machines

use Cpanel::JSON::XS;
my $json = new Cpanel::JSON::XS;
print $json->pretty(1)->encode(\%data);

YAML - for humans

use YAML qw(Dump Bless);
print Dump(\%data);

Perl and dates/times

read dates and make a DateTime object

use DateTime;
use DateTime::Format::Strptime;

# some common ones I've (unfortuneately) encountered

# YYYY-MM-DD
my $strp_dt_iso    = DateTime::Format::Strptime->new(
  pattern => '%F', on_error => 'croak'
);

# MM/DD/YYYY HH:MM:SS AM/PM (12h time)  
my $strp_dt_us_12h = DateTime::Format::Strptime->new(
  pattern => '%m/%d/%Y %I:%M:%S %p', on_error => 'croak'
);

# MM/DD/YYYY
my $strp_dt_us     = DateTime::Format::Strptime->new(
  pattern => '%m/%d/%Y', on_error => 'croak'
);

# DD-Mos-YY (month = 3 letter abbreviation)
my $strp_dt_crazy  = DateTime::Format::Strptime->new(
  pattern => '%d-%B-%y', on_error => 'croak'
);

# parse
$dt = $strp_dt_us->parse_datetime($this_data{date});

get current time?

use Time::localtime;
# time
my $now_time       = ctime();
# date
my $now_timestamp  = sprintf("%d-%d-%d", eval(localtime->year() + 1900),
  eval(localtime->mon() + 1), localtime->mday());

file modified time

use Time::localtime;
use File::stat;
$date_string = ctime(stat($file)->mtime);