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

Hi all, Here is the format of my text from which i need to grab some part of the text.

 
BEGIN hi
abc
def
ghi
jkl
END

BEGIN hello
abc
pqr
stu
mno
END

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As, you see above, each and every BEGIN has its own END, I want a snippet of the code from BEGIN hi to "its" END (not the end of "BEGIN hello"). The code i have written is shown below. But its pulling the lines from desired BEGIN to the END of the "other" BEGIN.

open DATA, "</hello.txt";
my @hello = <DATA>;
foreach my $k (@hello)
     {
if ($k=~/BEGIN ps7_slcr/../END/)
{
print $k;
}

    }

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Any solution? Thanks in Advance, Uday Sagar.

Replies are listed 'Best First'.
Re: Reading particular line which repeats itself many times in text
by choroba (Cardinal) on Jan 27, 2012 at 11:58 UTC
    If you want to use $k instead of $_, you have to use it everywhere: 
    if ($k =~ /BEGIN/ .. $k =~ /END/)

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Re: Reading particular line which repeats itself many times in text
by toolic (Bishop) on Jan 27, 2012 at 13:26 UTC
    Additionally, if your posted data actually had the string "ps7_slcr" in it, and if you were using warnings, you would have gotten warning messages of the type: 
    Use of uninitialized value $_ in pattern match (m//)

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Re: Reading particular line which repeats itself many times in text
by chessgui (Scribe) on Jan 28, 2012 at 08:30 UTC
    I don't know whether there is a fancy regular expression for this but in case where there are blocks I always use split (I consider it safer). 
    my @begin_blocks=split /BEGIN $name/,$string_containing_blocks;

my $block=$begin_blocks[1];

$block=~s/END\s*$//;

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    If there is no match '' is returned (since @begin_blocks now has only the zero index element: the string itself). This won't work if BEGIN blocks can contain the string 'BEGIN' inside them. If this is necessary you can use an escape sequence: replace all 'BEGIN'-s inside the block with 'BEGIN_'. If such a coding is used the search looks like this (add one line for decoding BEGIN_): 
    my @begin_blocks=split /BEGIN $name/,$string_containing_blocks;

my $block=$begin_blocks[1];

$block=~s/END\s*$//;

$block=~s/BEGIN_/BEGIN/g;

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      Monks, Thanks for your replies. I have solved the problem by putting together the concepts of non greedy quantifier(?) and storing the whole file (using File::Slurp) in a scalar variable. Here is the code.

      use File::Slurp;
local $/ = undef;
open FILE, "my_text.txt" or die "Couldn't open file: $!";
binmode FILE;
$string = <FILE>;
close FILE;

if ($string=~/BEGIN hi(.*?)END/s)
{
print ${1}."\n";
}

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