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Top Forums Shell Programming and Scripting if match found go to a particular line in perl Post 302180152 by era on Sunday 30th of March 2008 06:10:51 AM
Old 03-30-2008
Don't depend on me, I need to be going back to my day job soon.

There's a number of ways to do this, obviously. The old-fashioned variant would be to remember the previous line and print that when you see the terminator. The really brute Perl approach would be to slurp the whole file and substitute everything with an empty string except the line before the terminator. There's one in the Perl FAQ about that; perlfaq6 and scroll around for related questions. (The question about C comments further down the page has some hints, too.)

But the "previous line" solution is absolutely the simplest in this case, if you have no further requirements.

Code:
perl -ne 'BEGIN { $matching = 0; }
  $matching = 1 if (m/^\*Main Start/);
  next unless $matching;
  print $prev if (defined $prev && m/^\*Main End/);
  $prev = $_'

Not sure about the flow control you tried to describe. Are you supposed to remember everything from main start until main end and print that after the output from the last line before main end? (I guess this already qualifies as a pseudo-code implementation of what it takes. But then maybe I would consider a regex substitution over the whole file, or each *Main Start section, after all.)

Last edited by era; 03-30-2008 at 07:22 AM.. Reason: Add a Perl snippet for remembering previous line
 

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XML::LibXML::NodeList(3pm)				User Contributed Perl Documentation				XML::LibXML::NodeList(3pm)

NAME
XML::LibXML::NodeList - a list of XML document nodes DESCRIPTION
An XML::LibXML::NodeList object contains an ordered list of nodes, as detailed by the W3C DOM documentation of Node Lists. SYNOPSIS
my $results = $dom->findnodes('//somepath'); foreach my $context ($results->get_nodelist) { my $newresults = $context->findnodes('./other/element'); ... } API
new(@nodes) You will almost never have to create a new NodeList object, as it is all done for you by XPath. get_nodelist() Returns a list of nodes, the contents of the node list, as a perl list. string_value() Returns the string-value of the first node in the list. See the XPath specification for what "string-value" means. to_literal() Returns the concatenation of all the string-values of all the nodes in the list. get_node($pos) Returns the node at $pos. The node position in XPath is based at 1, not 0. size() Returns the number of nodes in the NodeList. pop() Equivalent to perl's pop function. push(@nodes) Equivalent to perl's push function. append($nodelist) Given a nodelist, appends the list of nodes in $nodelist to the end of the current list. shift() Equivalent to perl's shift function. unshift(@nodes) Equivalent to perl's unshift function. prepend($nodelist) Given a nodelist, prepends the list of nodes in $nodelist to the front of the current list. map($coderef) Equivalent to perl's map function. grep($coderef) Equivalent to perl's grep function. sort($coderef) Equivalent to perl's sort function. Caveat: Perl's magic $a and $b variables are not available in $coderef. Instead the two terms are passed to the coderef as arguments. reverse() Equivalent to perl's reverse function. foreach($coderef) Inspired by perl's foreach loop. Executes the coderef on each item in the list. Similar to "map", but instead of returning the list of values returned by $coderef, returns the original NodeList. reduce($coderef, $init) Equivalent to List::Util's reduce function. $init is optional and provides an initial value for the reduction. Caveat: Perl's magic $a and $b variables are not available in $coderef. Instead the two terms are passed to the coderef as arguments. perl v5.14.2 2012-06-20 XML::LibXML::NodeList(3pm)
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