reusable generic subroutines

[williey]

How do you create generic subroutines that are reusable in different scripts? I tried using "require" but it does not work out.

 

[vego]

And in your attempt, how did you "try" to require that did not work?

 

[williey]

This is the main script

use strict;
use warnings;
use DBI;

#  Subroutine : get_todays_date.pl
#
#  Syntax :    get_todays_date(format_type)  where format_type correlate to the 
#                                            below type code.
#
#  Description: return today's date in various formats.
#               new format can be added when needed.
#
#
# type   format       
# ----   ------
#   1    YYMMDD
#   2    MONTH-DD-YYYY
#       
#
#
#

require "test2.pl";

my $todays_date; 

$todays_date = get_todays_date(1);

print($todays_date);

$todays_date = get_todays_date(1);

print($todays_date);

The subroutine script

sub get_todays_date 
{
my ($date_format_type) = @_;

my $return_date;

# Date and time definition #

my ($second, $minute, $hour, $day, $month, $year, $weekday, $dayofyear, $isdst)=localtime;
my $yyyy = $year + 1900;
my $yy = substr($yyyy, 2,2);
my $mm = $month;
my $dd = $day;


my @months = ("January",
           "February",
           "March",
           "April",
           "May",
           "June",
           "July",
           "August",
           "September",
           "October",
           "November",
           "December");


if ($mm < 10)
{
  $mm = "0" . $mm;
}

if ($day < 10)
{
  $dd = "0" . $day;
}

if ($date_format_type == 1)
{ 
   $return_date = $yy . $mm . $ dd;
   return $return_date;
}
elsif ($date_format_type == 2)
{
   $return_date = uc(substr($months[$mm - 1], 0, 3)) . "-" . $dd . "-" . $yyyy;
   return $return_date;
}

}

 

[Nebbish]

Actually this is closely related to what I was about to ask about (and will in a different post). What you want is the Exporter module. Make a separate file named globalFunctions.pm (or whatever.pm), and do the following:

package globalFunctions;

use Exporter;
@ISA = ('Exporter');

@EXPORT = qw($string @array %hash &function);

$string = "hello, global string.";
@array = (1,2,3,4);
%hash = (
 "A" => "B",
);

sub function {
  print "this is my function that can be used anywhere.";
}

1;

Now, whenever you want to use these scalars, arrays, hashes, or functions, just put "use globalFunctions;" at the top of your script. A few warnings:

a) Make sure Perl knows where to find your globalFunctions.pm file. If you want to put it in your own private directory, put "use lib 'c:/directory/';" at the top of your script so Perl knows to look there. Check out @INC for more on where Perl looks for modules.

b) Make sure the 1; is at the end

c) Don't define the variables as "my" in your globalFunctions file.

d) Put whatever you want to export in the @EXPORT array, otherwise the exporter won't know to ship it out.

Hope that helps,

Nick

 

[williey]

Thanks for the tips.

Here is my revised code

#  Subroutine : get_todays_date.pl
#
#  Syntax :    get_todays_date(format_type)  where format_type correlate to the 
#                                            below type code.
#
#  Description: return today's date in various formats.
#               new format can be added when needed.
#
#
# type   format       
# ----   ------
#   1    YYMMDD
#   2    MONTH-DD-YYYY
#       
#
#
#


my $todays_date; 

$todays_date = get_todays_date(1);

print($todays_date);

$todays_date = get_todays_date(1);

print($todays_date);

package dateFunctions;

use Exporter
@ISA = ('Exporter');

@EXPORT = qw(&get_todays_date);


sub get_todays_date 
{
$date_format_type = @_;

$return_date;

# Date and time definition #

($second, $minute, $hour, $day, $month, $year, $weekday, $dayofyear, $isdst)=localtime;
$yyyy = $year + 1900;
$yy = substr($yyyy, 2,2);
$mm = $month;
$dd = $day;


@months = ("January",
           "February",
           "March",
           "April",
           "May",
           "June",
           "July",
           "August",
           "September",
           "October",
           "November",
           "December");


if ($mm < 10)
{
  $mm = "0" . $mm;
}

if ($day < 10)
{
  $dd = "0" . $day;
}

if ($date_format_type == 1)
{ 
   $return_date = $yy . $mm . $ dd;
   return $return_date;
}
elsif ($date_format_type == 2)
{
   $return_date = uc(substr($months[$mm - 1], 0, 3)) . "-" . $dd . "-" . $yyyy;
   return $return_date;
}

}

1;

when I try to execute the script, it cannot find the function. "Undefined subroutine &main::get_todays_date called at test1.pl line 30.

 

[Nebbish]

Williey,

You need to have your dateFunctions.pm in a location where Perl can find it, and you need to have "use dateFunctions;" at the top of whatever script wants to use it. That's what I was babbling about with the @INC and use lib 'c:/dir/'; stuff in my earlier post.

-Nick

 

[williey]

Thanks Nick.

Got it to run after I discover I was missing the ";" after
"use Exporter".

However, the dates returned at incorrect. With the following warning.
"Useless use of a variable in void context at dateFunctions.pm line 13."

package dateFunctions;

use Exporter;
@ISA = ('Exporter');

@EXPORT = qw(&get_todays_date);


sub get_todays_date 
{
$date_format_type = @_;

$return_date;     <------- line 13

# Date and time definition #

($second, $minute, $hour, $day, $month, $year, $weekday, $dayofyear, $isdst)=localtime;
$yyyy = $year + 1900;
$yy = substr($yyyy, 2,2);
$mm = $month;
$dd = $day;


@months = ("January",
           "February",
           "March",
           "April",
           "May",
           "June",
           "July",
           "August",
           "September",
           "October",
           "November",
           "December");


if ($mm < 10)
{
  $mm = "0" . $mm;
}

if ($day < 10)
{
  $dd = "0" . $day;
}

if ($date_format_type == 1)
{ 
   $return_date = $yy . $mm . $ dd;
   return $return_date;
}
elsif ($date_format_type == 2)
{
   $return_date = uc(substr($months[$mm - 1] , 0, 3)) . "-" . $dd . "-" . $yyyy;
   return $return_date;
}

}

1;

 

[mikevh]

willey, this works just fine with require, with a few small changes.

1. The months returned by localtime are numbered 0-11, not 1-12.

2. The file test2.pl must have a 1; as the last line of code. (The file, not the sub.)
Note the bolded changes below:

sub get_todays_date 
{
my ($date_format_type) = @_;

my $return_date;

# Date and time definition #

my ($second, $minute, $hour, $day, $month, $year, $weekday, $dayofyear, $isdst)=localtime;
my $yyyy = $year + 1900;
my $yy = substr($yyyy, 2,2);
[b]my $mm = $month + 1;[/b]
my $dd = $day;


my @months = ([b]undef,[/b]
           "January",
           "February",
           "March",
           "April",
           "May",
           "June",
           "July",
           "August",
           "September",
           "October",
           "November",
           "December");


if ($mm < 10)
{
  $mm = "0" . $mm;
}

if ($day < 10)
{
  $dd = "0" . $day;
}

if ($date_format_type == 1)
{ 
   $return_date = $yy . $mm . $ dd;
   return $return_date;
}
elsif ($date_format_type == 2)
{
   $return_date = uc(substr($months[[b]$mm[/b]], 0, 3)) . "-" . $dd . "-" . $yyyy;
   return $return_date;
}
} 
[b]1;[/b]

In your main program, add a "\n" at the end of your print statements so everything doesn't print on the same line, i.e.,

$todays_date = get_todays_date(1);

print($todays_date, [b]"\n"[/b]);

$todays_date = get_todays_date(2);

print($todays_date, [b]"\n"[/b]);

Here's the output:[
040916
SEP-16-2004

This looks like what you intended, no?

 

[williey]

Thanks Mike!
I got it the work with "require". So which is the better method? to use "require" or create a package instead?

 

[mikevh]

A big question. I think the documentation covers this more completely than I could hope to. See

perldoc perlmod
perldoc -f use
perldoc -f require

My point was that it wasn't necessary to make it a module in order to get it to work. The problem was caused by minor things in the test2.pl file, not the fact that it wasn't a module. Fix the problems in test2.pl, and it works fine with require.

Modules are certainly "cooler," and they are a sine qua non for Perl OO programming. Require is easier to use. It depends on what you want, and what you need.