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Full Discussion: What "set +u" does?
Top Forums UNIX for Advanced & Expert Users What "set +u" does? Post 302149324 by gus2000 on Wednesday 5th of December 2007 03:39:14 PM
Old 12-05-2007
Using "set -u" can be nasty. It's a way to force you to declare all your variables before using them, which is good programming practice. Referencing any unset variable will force the script to exit.

Unfortuantely this means you cannot even test if a variable is set without making the shell blow up. In these cases I usually see some piece of code framed by "set +u" and "set -u" again, which is ugly. If you have "set -u" active, then you should reference any external variables of unknown state like this:

Code:
VALUE=${unknownvar:-}

The shell uses the above syntax to return a default value when "unknownvar" is not set or is null. Since the default value is omited, it returns null but does NOT cause the shell to exit.
 

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Mason::Manual::Intro(3pm)				User Contributed Perl Documentation				 Mason::Manual::Intro(3pm)

NAME
Mason::Manual::Intro - Getting started with Mason DESCRIPTION
A few quick examples to get your feet wet with Mason. See Mason::Manual::Setup for how to use Mason to generate web sites. EXAMPLE 1 Hello world (from command-line) After installing Mason, you should have a "mason" command in your installation path (e.g. "/usr/local/bin"). Try this: % mason Hello! The local time is <% scalar(localtime) %>. ^D (where '^D' means ctrl-D or EOF). You should see something like Hello! The local time is Wed Mar 2 17:11:54 2011. The "mason" command reads in a Mason component (template), runs it, and prints the result to standard output. Notice that the tag <% scalar(localtime) %> was replaced with the value of its expression. This is called a substitution tag and is a central piece of Mason syntax. EXAMPLE 2 Email generator (from script) The command line is good for trying quick things, but eventually you're going to want to put your Mason components in files. In a test directory, create a directory "comps" and create a file "email.mc" with the following: <%class> has 'amount'; has 'name'; </%class> Dear <% $.name %>, We are pleased to inform you that you have won $<% sprintf("%.2f", $.amount) %>! Sincerely, The Lottery Commission <%init> die "amount must be a positive value!" unless $.amount > 0; </%init> In addition to the substitution tag we've seen before, we declare two attributes, "amount" and "name", to be passed into the component; and we declare a piece of initialization code to validate the amount. In the same test directory, create a script "test.pl" with the following: 1 #!/usr/local/bin/perl 2 use Mason; 3 my $interp = Mason->new(comp_root => 'comps', data_dir => 'data'); 4 print $interp->run('/email', name => 'Joe', amount => '1500')->output; Line 3 creates a Mason interpreter, the main Mason object. It specifies two parameters: a component root, indicating the directory hierarchy where your components will live; and a data directory, which Mason will use for internal purposes such as class generation and caching. Line 4 runs the template - notice that the ".mc" extension is added automatically - passing values for the "name" and "amount" attributes. Run "test.pl", and you should see Dear Joe, We are pleased to inform you that you have won $1500.00! Sincerely, The Lottery Commission SEE ALSO
Mason::Manual::Tutorial, Mason::Manual AUTHOR
Jonathan Swartz <swartz@pobox.com> COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by Jonathan Swartz. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. perl v5.14.2 2012-05-02 Mason::Manual::Intro(3pm)
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