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how to extract characters between 2 pipes

mauto
User

Aug 1, 2002, 9:07 AM

Post #1 of 11 (3614 views)

how to extract characters between 2 pipes	Can't Post

mhx
Enthusiast

Aug 1, 2002, 9:33 AM

Post #2 of 11 (3613 views)

Re: [mauto] how to extract characters between 2 pipes [In reply to]	Can't Post

Code

$str = '|abcdefg|hijk|abc|pqr|xyz'; 
($abc) = $str =~ /\|([^|]*)/; 
print $abc;

Hope this helps.

-- mhx

At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice. "I will take the Ring," he said, "though I do not know the way."

-- Frodo

mauto
User

Aug 1, 2002, 10:26 AM

Post #3 of 11 (3605 views)

Re: [mhx] how to extract characters between 2 pipes [In reply to]	Can't Post

mhx
Enthusiast

Aug 1, 2002, 12:38 PM

Post #4 of 11 (3603 views)

Re: [mauto] how to extract characters between 2 pipes [In reply to]	Can't Post

You could use the following:

Code

$str = '|abcdefg|hijk|abc|pqr|xyz'; 
$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//; 
print $count;

But that depends more or less upon what else you want to know about the string.

-- mhx

At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice. "I will take the Ring," he said, "though I do not know the way."

-- Frodo

Paul
Enthusiast

Aug 1, 2002, 6:47 PM

Post #5 of 11 (3601 views)

Re: [mhx] how to extract characters between 2 pipes [In reply to]	Can't Post

>>
$str = '|abcdefg|hijk|abc|pqr|xyz';
($abc) = $str =~ /\|([^|]*)/;
print $abc;
<<

I wouldn't use a regex for that.

Code

    my $str = '|abcdefg|hijk|abc|pqr|xyz';  
    my $abc = (split /\|/, $str, 3)[1];  
    print $abc;

mhx
Enthusiast

Aug 1, 2002, 9:51 PM

Post #6 of 11 (3599 views)

Re: [RedRum] how to extract characters between 2 pipes [In reply to]	Can't Post

In Reply To

I wouldn't use a regex for that.

Well, I would. Tongue

In Reply To

Code

my $abc = (split /\|/, $str, 3)[1];

If $str gets longer, this solution will get slower (it's just about the same for the given example, at least on my machine). The regex solution does not depend on the length of $str and it's IMHO also easier to read. Optimizing the regex to

Code

($abc) = $str =~ /^\|([^|]*)/;

even makes it faster than the split solution.

Besides, it's shorter. Wink

-- mhx

At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice. "I will take the Ring," he said, "though I do not know the way."

-- Frodo

mauto
User

Aug 2, 2002, 3:41 AM

Post #7 of 11 (3593 views)

Re: [RedRum] how to extract characters between 2 pipes [In reply to]	Can't Post

Code

$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//;

Thanks.

Can you explain the above regex in words, as i am a little confused ?

jryan
User

Aug 2, 2002, 3:33 PM

Post #8 of 11 (3588 views)

Re: [mauto] how to extract characters between 2 pipes [In reply to]	Can't Post

Code

 
my $text = q(|abcdefg|hijk|abc|pqr|xyz); 
sub bars_before{ substr($text, 0, index($text,shift)) =~ tr/|// } 
 
print bars_before('pqr');

mhx
Enthusiast

Aug 5, 2002, 5:12 AM

Post #9 of 11 (3575 views)

Re: [mauto] how to extract characters between 2 pipes [In reply to]	Can't Post

In Reply To

Can you explain the above regex in words, as i am a little confused?

Sure. The part in red captures the whole string before pqr:

Code

$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//;

That alone is a very basic regex. The .* matches zero or more arbitrary characters. The parentheses around .* capture the string that .* matched.

Code

$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//;

Putting parentheses around the regex makes the regex operator work in list context, returning a list of all matched substrings. The index operator [0] simply selects the first (and only) element of that list, which is the string holding everything before pqr.

Code

$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//;

Now, this string is used with the transliteration operator tr, which is normally used to replace certain characters. If no replacement characters are given, the operator simply counts the characters (in our case pipes) and returns the total count, which is then stored in $count.

You can have a look at [url=http://www.perldoc.com/perl5.8.0/pod/perlop.html#Regexp-Quote-Like-Operators]perldoc perlop for details.

Hope this helps.

-- mhx

At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice. "I will take the Ring," he said, "though I do not know the way."

-- Frodo

mauto
User

Aug 6, 2002, 5:14 AM

Post #10 of 11 (3565 views)

Re: [mhx] how to extract characters between 2 pipes [In reply to]	Can't Post

Code

$str = '|abcdefg|hijk|abc|pqr|xyz|abc_pqr|ghi';  
$count = ($str =~ /(.*)pqr/)[0] =~ tr/|//;  
print $count;

$count = 6

How can I modify the regex to ensure that only pqr is matched ?

mhx
Enthusiast

Aug 6, 2002, 6:25 AM

Post #11 of 11 (3562 views)

Re: [mauto] how to extract characters between 2 pipes [In reply to]	Can't Post

Code

$str = '|abcdefg|hijk|abc|pqr|xyz|abc_pqr|ghi'; 
$count = ($str =~ /(.*?\|)pqr/)[0] =~ tr/|//;

The explicit \| will ensure that the pqr is directly behind a pipe symbol.
The ? will ensure that the first occurrence of pqr is used, as it modifies the * quantifier to match as few as possible characters, instead of as many as possible, which is the default.

Hope this helps.

-- mhx

At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice. "I will take the Ring," he said, "though I do not know the way."

-- Frodo

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