Finding the second line an item appears on

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Finding the second line an item appears on by Abigail-II (Bishop) on Oct 27, 2003 at 16:56 UTC
You're almost there: `#!/usr/bin/perl use strict; use warnings; my $count; do {$_ = <DATA>; print} until /formulae/ && ++ $count == 2; __DATA__ One line two line formulae blue line red line formulae more line more line formulae final line` [download] That will print: `One line two line formulae blue line red line formulae` [download] Abigail	[reply] [d/l] [select]
Re: Finding the second line an item appears on by dreadpiratepeter (Priest) on Oct 27, 2003 at 16:42 UTC
`my $cnt=0; while (my $line = <>) { $cnt++ if $line =~ /formulae/; last if $cnt>1; } if ($cnt>1) { # got what we wanted } else { # word didn't appear twice }` [download] I'm sure it can be done more succinctly, but this should make obvious what is going on. UPDATE: ops! thanks Albannach. fixed code above. -pete "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."	[reply] [d/l]
Re: Finding the second line an item appears on by hardburn (Abbot) on Oct 27, 2003 at 17:03 UTC
Copy-and-paste your search to the line just below it: `do { $_ = <> } until /formulae/; do { $_ = <> } until /formulae/;` [download] Sure, it isn't fancy, but it doesn't rely on any counter variables, either. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer `:(){ :\|:&};:` Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]
Re: Finding the second line an item appears on by monktim (Friar) on Oct 27, 2003 at 18:48 UTC
The other answers look good if formulae is guaranteed to exist on at most 1 line at a time. If it can appear twice on the same line, this will work. `use strict; my $i; while (<DATA>) { my @m = ($_ =~ /formulae/g); $i += @m; } print "Found $i matches\n"; __DATA__ message one message two formulae formulae message threee` [download]	[reply] [d/l]
Re: second match... by Anonymous Monk on Oct 27, 2003 at 17:18 UTC
`while(<>){print&&(/formula/.../formula/)=~/E0$/&&last}` [download]	[reply] [d/l]
Re: Finding the second line an item appears on by Anonymous Monk on Oct 27, 2003 at 16:44 UTC
Many ways of doing this, for instance, this is rather inelegant but shows the logic clearly: `my $count = 0; while (<>) { if (/formulae/) { $count++; } if ($count == 2) { print "Found 2nd\n"; } }` [download] Or you can just change your do-loop a bit: `$count = 0; do {$count++; $_ = <> } until ((/formulae/) && ($count == 2))` [download]	[reply] [d/l] [select]
Re: Re: Finding the second line an item appears on by dreadpiratepeter (Priest) on Oct 27, 2003 at 16:52 UTC
Your second example doesn't work. It will match the third line, if it contains formulae, otherwise it will fail. -pete "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."	[reply]
Re: Finding the second line an item appears on by Art_XIV (Hermit) on Oct 27, 2003 at 16:47 UTC
This is a bit brute force, but I'm sure one of the other monks has a more elegant way... `my @matches; while (<FILE>) { push @matches, $_ if /formulae/; last if scalar @matches == 2; }` [download] You'd be out of luck with this one, though, if 'formulae' could occur more than once per line and still have to stop.	[reply] [d/l]


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