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Top Forums UNIX for Beginners Questions & Answers What is the meaning the $ special character? Post 303006460 by Scrutinizer on Thursday 2nd of November 2017 11:21:05 AM
Old 11-02-2017
Hi see here: The Open Group Base Specifications Issue 7, 2016 Edition

Quote:
In the shell command language, an entity that stores values. There are three types of parameters: variables (named parameters), positional parameters, and special parameters. Parameter expansion is accomplished by introducing a parameter with the '$' character.
Note:
See also XCU Parameters and Variables.

--
"Parameter expansion" is the way to get the value that is stored in a parameter ( for example a variable )

So for example if you have a variable foo and you give it the value bar
Code:
foo=bar

, then the variable foo contains the value bar.
Then, to get the content of the variable foo, you prepend a $ sign:
Code:
echo "$foo"
bar


Last edited by Scrutinizer; 11-02-2017 at 12:28 PM..
 

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Template::Plugin::URL(3pm)				User Contributed Perl Documentation				Template::Plugin::URL(3pm)

NAME
Template::Plugin::URL - Plugin to construct complex URLs SYNOPSIS
[% USE url('/cgi-bin/foo.pl') %] [% url(debug = 1, id = 123) %] # ==> /cgi/bin/foo.pl?debug=1&id=123 [% USE mycgi = url('/cgi-bin/bar.pl', mode='browse', debug=1) %] [% mycgi %] # ==> /cgi/bin/bar.pl?mode=browse&debug=1 [% mycgi(mode='submit') %] # ==> /cgi/bin/bar.pl?mode=submit&debug=1 [% mycgi(debug='d2 p0', id='D4-2k[4]') %] # ==> /cgi-bin/bar.pl?mode=browse&debug=d2%20p0&id=D4-2k%5B4%5D DESCRIPTION
The "URL" plugin can be used to construct complex URLs from a base stem and a hash array of additional query parameters. The constructor should be passed a base URL and optionally, a hash array reference of default parameters and values. Used from with a template, it would look something like the following: [% USE url('http://www.somewhere.com/cgi-bin/foo.pl') %] [% USE url('/cgi-bin/bar.pl', mode='browse') %] [% USE url('/cgi-bin/baz.pl', mode='browse', debug=1) %] When the plugin is then called without any arguments, the default base and parameters are returned as a formatted query string. [% url %] For the above three examples, these will produce the following outputs: http://www.somewhere.com/cgi-bin/foo.pl /cgi-bin/bar.pl?mode=browse /cgi-bin/baz.pl?mode=browse&debug=1 Note that additional parameters are separated by '"&"' rather than simply '"&"'. This is the correct behaviour for HTML pages but is, unfortunately, incorrect when creating URLs that do not need to be encoded safely for HTML. This is likely to be corrected in a future version of the plugin (most probably with TT3). In the mean time, you can set $Template::Plugin::URL::JOINT to "&" to get the correct behaviour. Additional parameters may be also be specified to the URL: [% url(mode='submit', id='wiz') %] Which, for the same three examples, produces: http://www.somewhere.com/cgi-bin/foo.pl?mode=submit&id=wiz /cgi-bin/bar.pl?mode=browse&id=wiz /cgi-bin/baz.pl?mode=browse&debug=1&id=wiz A new base URL may also be specified as the first option: [% url('/cgi-bin/waz.pl', test=1) %] producing /cgi-bin/waz.pl?test=1 /cgi-bin/waz.pl?mode=browse&test=1 /cgi-bin/waz.pl?mode=browse&debug=1&test=1 The ordering of the parameters is non-deterministic due to fact that Perl's hashes themselves are unordered. This isn't a problem as the ordering of CGI parameters is insignificant (to the best of my knowledge). All values will be properly escaped thanks to some code borrowed from Lincoln Stein's "CGI" module. e.g. [% USE url('/cgi-bin/woz.pl') %] [% url(name="Elrich von Benjy d'Weiro") %] Here the spaces and ""'"" character are escaped in the output: /cgi-bin/woz.pl?name=Elrich%20von%20Benjy%20d%27Weiro An alternate name may be provided for the plugin at construction time as per regular Template Toolkit syntax. [% USE mycgi = url('cgi-bin/min.pl') %] [% mycgi(debug=1) %] AUTHOR
Andy Wardley <abw@wardley.org> <http://wardley.org/> COPYRIGHT
Copyright (C) 1996-2007 Andy Wardley. All Rights Reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. SEE ALSO
Template::Plugin perl v5.14.2 2011-12-20 Template::Plugin::URL(3pm)
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