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Full Discussion: stack problem
Top Forums UNIX for Dummies Questions & Answers stack problem Post 18454 by mastaCow on Thursday 28th of March 2002 12:26:27 PM
Old 03-28-2002
stack problem

Hi,
I'm a complete beginner at all this business so any help is appreciated.

I have a script (not written by me) which I need to modify. My problems is....

tail -1c $file

.... I understand this will return the final character of the $file variable. I need to make it return the first character of the $file variable. I've already tried first, top, front etc. but non seem to work.

And please don't ask what version of unix i'm running - all I do is boot up windows and use a program called Exceed.

Cheers for any help.
mastaCow
 

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Padre::Document::Perl::Beginner(3pm)			User Contributed Perl Documentation		      Padre::Document::Perl::Beginner(3pm)

NAME
Padre::Document::Perl::Beginner - naive implementation of some beginner specific error checking SYNOPSIS
use Padre::Document::Perl::Beginner; my $beginner = Padre::Document::Perl::Beginner->new; if (not $beginner->check($data)) { warn $beginner->error; } DESCRIPTION
This is a naive implementation. It needs to be replaced by one using PPI. In Perl 5 there are lots of pitfalls the unaware, especially the beginner can easily fall in. While some might expect the Perl compiler itself would catch those it does not (yet ?) do it. So we took the initiative and added a beginners mode to Padre in which these extra issues are checked. Some are real problems that would trigger an error anyway we just make them a special case with a more specific error message. (e.g. "use warning;" without the trailing s) Others are valid code that can be useful in the hands of a master but that are poisonous when written by mistake by someone who does not understand them. (e.g. "if ($x = /value/) { }" ). This module provides a method called "check" that can check a Perl script (provided as parameter as a single string) and recognize problematic code. Examples See <http://padre.perlide.org/ticket/52> and <http://www.perlmonks.org/?node_id=728569> Cases o split /,/, @data; Here @data is in scalar context returning the number of elements. Spotted in this form: split /,/, @ARGV; o use warning; s is missing at the end. o map { $_; } (@items),$extra_item; is the same as map { $_; } (@items,$extra_item); but you usually want (map { $_; } (@items)),$extra_item; which means: map all @items and them add $extra_item without mapping it. o Warn about Perl-standard package names being reused package DB; o $x = chomp $y; print chomp $y; o map { s/foo/bar/; } (@items); This returns an array containing true or false values (s/// - return value). Use map { s/foo/bar/; $_; } (@items); to actually change the array via s///. o <@X> o if ($x = /bla/) { } o Pipe | in open() not at the end or the beginning. o open($ph, "| something |"); o Regular expression starting with a quantifier such as /+.../ o } else if { o } elseif { o close; HOW TO ADD ANOTHER ONE
Please feel free to add as many checks as you like. This is done in three steps: Add the test Add one (or more) tests for this case to t/75-perl-beginner.t The test should be successful when your supplied sample fails the check and returns the correct error message. As texts of error messages may change, try to match a good part which allows identification of the message but don't match the very exact text. Tests could use either one-liners written as strings within the test file or external support files. There are samples for both ways in the test script. Add the check Add the check to the check-sub of this file (Document/Perl/Beginner.pm). There are plenty samples here. Remember to add a sample (and maybe short description) what would fail the test. Run the test script to match your test case(s) to the new check. Add the configuration option Go to Config.pm, look for the beginner error checks configuration and add a new setting for your new check there. It defaults to 1 (run the check), but a user could turn it off by setting this to 0 within the Padre configuration file. COPYRIGHT &; LICENSE Copyright 2008-2012 The Padre development team as listed in Padre.pm. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of the license can be found in the LICENSE file included with this module. perl v5.14.2 2012-06-27 Padre::Document::Perl::Beginner(3pm)

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