I am using Perl to do some prototyping.
I need an expression to replace e by [ee] if the string is exactly 2 chars and finishes by "e".
le -> l [ee]
me -> m [ee]
elle -> elle : no change
I cannot test the length of the string, I need one expression to do the whole job.
I tried:
`s/(?=^.{0,2}\z).*e\z%/[ee]/g` but this is replacing the whole string
`s/^[c|d|j|l|m|n|s|t]e$/[ee]/g` same result (I listed the possible letters that could precede my "e")
`^(?<=[c|d|j|l|m|n|s|t])e$/[ee]/g` but I have no match, not sure I can use ^ on a positive look behind
EDIT
Guys you're amazing, hours of search on the web and here I get answers minutes after I posted.
I tried all your solutions and they are working perfectly directly in my script, i.e. this one:
my $test2="le";
$test2=~ s/^(\S)e$/\1\[ee\]/g;
print "test2:".$test2."\n";
-> test2:l[ee]
But I am loading these regex from a text file (using Perl for proto, the idea is to reuse it with any language implementing regex):
In the text file I store for example (I used % to split the line between match and replace):
^(\S)e$% \1\[ee\]
and then I parse and apply all regex like that:
my $test="le";
while (my $row = <$fh>) {
chomp $row;
if( $row =~ /%/){
my #reg = split /%/, $row;
#if no replacement, put empty string
if($#reg == 0){
push(#reg,"");
}
print "reg found, reg:".$reg[0].", replace:".$reg[1]."\n";
push #regs, [ #reg ];
}
}
print "orgine:".$test."\n";
for my $i (0 .. $#regs){
my $p=$regs[$i][0];
my $r=$regs[$i][1];
$test=~ s/$p/$r/g;
}
print "final:".$test."\n";
This technique is working well with my other regex, but not yet when I have a $1 or \1 in the replace... here is what I am obtaining:
final:\1\ee\
PS: you answered to initial question, should I open another post ?
Something like s/(?i)^([a-z])e$/$1[ee]/
Why aren't you using a capture group to do the replacement?
`s/^([c|d|j|l|m|n|s|t])e$/\1 [ee]/g`
If those are the characters you need and if it is indeed one word to a line with no whitespace before it or after it, then this will work.
Here's another option depending on what you are looking for. It will match a two character string consisting of one a-z character followed by one 'e' on its own line with possible whitespace before or after. It will replace this will the single a-z character followed by ' [ee]'
`s/^\s*([a-z])e\s*$/\1 [ee]/`
^(\S)e$
Try this.Replace by $1 [ee].See demo.
https://regex101.com/r/hR7tH4/28
I'd do something like this
$word =~ s/^(\w{1})(e)$/$1$2e/;
You can use following regex which match 2 character and then you can replace it with $1\[$2$2\]:
^([a-zA-Z])([a-zA-Z])$
Demo :
$my_string =~ s/^([a-zA-Z])([a-zA-Z])$/$1[$2$2]/;
See demo https://regex101.com/r/iD9oN4/1
Related
I have a strings and need to extract only icnnumbers/numbers from them.
icnnumber:9876AB54321_IN
number:987654321FR
icnnumber:987654321YQ
I need to extract below data from above example.
9876AB54321
987654321FR
987654321YQ
Here is my regex, but its working for first line of data.
(icnnumber|number):(\w+)(?:_IN)
How can I have expression which would match for three set of data.
Given your strings to extract are only upper case and numeric, why use \w when that also matches _?
How about just matching:
#!/usr/bin/env perl
use strict;
use warnings;
while (<DATA>) {
m/number:([A-Z0-9]+)/;
print "$1\n";
}
__DATA__
icnnumber:9876AB54321_IN
number:987654321FR
icnnumber:987654321YQ
Another alternative to get only the values as a match using \K to reset the match buffer
\b(?:icn)?number:\K[^\W_]+
Regex demo | Perl demo
For example
my $str = 'icnnumber:9876AB54321_IN
number:987654321FR
icnnumber:987654321YQ';
while($str =~ /\b(?:icn)?number:\K[^\W_]+/g ) {
print $& . "\n";
}
Output
9876AB54321
987654321FR
987654321YQ
You may replace \w (that matches letters, digits and underscores) with [^\W_] that is almost the same, but does not match underscores:
(icnnumber|number):([^\W_]+)
See the regex demo.
If you want to make sure icnnumber and number are matched as whole words, you may add a word boundary at the start:
\b(icnnumber|number):([^\W_]+)
^^
You may even refactor the pattern a bit in order not to repeat number using an optional non-capturing group, see below:
\b((?:icn)?number):([^\W_]+)
^^^^^^^^
Pattern details
\b - a word boundary (immediately to the right, there must be start of string or a char other than letter, digit or _)
((?:icn)?number) - Group 1: an optional sequence of icn substring and then number substring
: - a : char
([^\W_]+) - Group 2: one or more letters or digits.
Just another suggestion maybe, but if your strings are always valid, you may consider just to split on a character class and pull the second index from the resulting array:
my $string= "number:987654321FR";
my #part = (split /[:_]/, $string)[1];
print #part
Or for the whole array of strings:
#Array = ("icnnumber:9876AB54321_IN", "number:987654321FR", "icnnumber:987654321YQ");
foreach (#Array)
{
my $el = (split /[:_]/, $_)[1];
print "$el\n"
}
Results in:
9876AB54321
987654321FR
987654321YQ
Regular expression can have 'icn' as an option and part of the interest is 11 characters after :.
my $re = qr/(icn)?number:(.{11})/;
Test code snippet
use strict;
use warnings;
use feature 'say';
my $re = qr/(icn)?number:(.{11})/;
while(<DATA>) {
say $2 if /$re/;
}
__DATA__
icnnumber:9876AB54321_IN
number:987654321FR
icnnumber:987654321YQ
Output
9876AB54321
987654321FR
987654321YQ
Already you got best and better answers here anyway I trying to solve your question right now.
Get the whole string,
my $str = do { local $/; <DATA> }; #print $str;
You can check the first grouping method upto _ or \b from the below line,
#arrs = ($str=~m/number\:((?:(?!\_).)*)(?:\b|\_)/ig);
(or)
You can check the non-words \W and _ for the first grouping here, and pushing the matches in the array
#arrs = ($str=~m/number\:([^\W\_]+)(?:\_|\b)/ig);
print the output
print join "\n", #arrs;
__DATA__
icnnumber:9876AB54321_IN
number:987654321FR
icnnumber:987654321YQ
I'm having difficulty writing a Perl program to extract the word following a certain word.
For example:
Today i'm not going anywhere except to office.
I want the word after anywhere, so the output should be except.
I have tried this
my $words = "Today i'm not going anywhere except to office.";
my $w_after = ( $words =~ /anywhere (\S+)/ );
but it seems this is wrong.
Very close:
my ($w_after) = ($words =~ /anywhere\s+(\S+)/);
^ ^ ^^^
+--------+ |
Note 1 Note 2
Note 1: =~ returns a list of captured items, so the assignment target needs to be a list.
Note 2: allow one or more blanks after anywhere
In Perl v5.22 and later, you can use \b{wb} to get better results for natural language. The pattern could be
/anywhere\b{wb}.+?\b{wb}(.+?\b{wb})/
"wb" stands for word break, and it will account for words that have apostrophes in them, like "I'll", that plain \b doesn't.
.+?\b{wb}
matches the shortest non-empty sequence of characters that don't have a word break in them. The first one matches the span of spaces in your sentence; and the second one matches "except". It is enclosed in parentheses, so upon completion $1 contains "except".
\b{wb} is documented most fully in perlrebackslash
First, you have to write parentheses around left side expression of = operator to force array context for regexp evaluation. See m// and // in perlop documentation.[1] You can write
parentheses also around =~ binding operator to improve readability but it is not necessary because =~ has pretty high priority.
Use POSIX Character Classes word
my ($w_after) = ($words =~ / \b anywhere \W+ (\w+) \b /x);
Note I'm using x so whitespaces in regexp are ignored. Also use \b word boundary to anchor regexp correctly.
[1]: I write my ($w_after) just for convenience because you can write my ($a, $b, $c, #rest) as equivalent of (my $a, my $b, my $c, my #rest) but you can also control scope of your variables like (my $a, our $UGLY_GLOBAL, local $_, #_).
This Regex to be matched:
my ($expect) = ($words=~m/anywhere\s+([^\s]+)\s+/);
^\s+ the word between two spaces
Thanks.
If you want to also take into consideration the punctuation marks, like in:
my $words = "Today i'm not going anywhere; except to office.";
Then try this:
my ($w_after) = ($words =~ /anywhere[[:punct:]|\s]+(\S+)/);
I have a file with submissions like this
%TRYYVJT128F93506D3<SEP>SOYKCDV12AB0185D99<SEP>Rainie Yang<SEP>Ai Wo Qing shut up (OT: Shotgun(Aka Shot Gun))
%TRYYVHU128F933CCB3<SEP>SOCCHZY12AB0185CE6<SEP>Tepr<SEP>Achète-moi
I am stripping everything but the song name by using this regex.
$line =~ s/.*>|([([\/\_\-:"``+=*].*)|(feat.*)|[?¿!¡\.;&\$#%#\\|]//g;
I want to make sure that the only strings printed are ones that contain only English characters, so in this case it would the first song title Ai Wo Quing shut up and not the next one because of the è.
I have tried this
if ( $line =~ m/[^a-zA-z0-9_]*$/ ) {
print $line;
}
else {
print "Non-english\n";
I thought this would match just the English characters, but it always prints Non-english. I feel this is me being rusty with regex, but I cannot find my answer.
Following from the comments, your problem would appear to be:
$line =~ m/[^a-zA-z0-9_]*$/
Specifically - the ^ is inside the brackets, which means that it's not acting as an 'anchor'. It's actually a negation operator
See: http://perldoc.perl.org/perlrecharclass.html#Negation
It is also possible to instead list the characters you do not want to match. You can do so by using a caret (^) as the first character in the character class. For instance, [^a-z] matches any character that is not a lowercase ASCII letter, which therefore includes more than a million Unicode code points. The class is said to be "negated" or "inverted".
But the important part is - that without the 'start of line' anchor, your regular expression is zero-or-more instances (of whatever), so will match pretty much anything - because it can freely ignore the line content.
(Borodin's answer covers some of the other options for this sort of pattern match, so I shan't reproduce).
It's not clear exactly what you need, so here are a couple of observations that speak to what you have written.
It is probably best if you use split to divide each line of data on <SEP>, which I presume is a separator. Your question asks for the fourth such field, like this
use strict;
use warnings;
use 5.010;
while ( <DATA> ) {
chomp;
my #fields = split /<SEP>/;
say $fields[3];
}
__DATA__
%TRYYVJT128F93506D3<SEP>SOYKCDV12AB0185D99<SEP>Rainie Yang<SEP>Ai Wo Qing shut up (OT: Shotgun(Aka Shot Gun))
%TRYYVHU128F933CCB3<SEP>SOCCHZY12AB0185CE6<SEP>Tepr<SEP>Achète-moi
output
Ai Wo Qing shut up (OT: Shotgun(Aka Shot Gun))
Achète-moi
Also, the word character class \w matches exactly [a-zA-z0-9_] (and \W matches the complement) so you can rewrite your if statement like this
if ( $line =~ /\W/ ) {
print "Non-English\n";
}
else {
print $line;
}
I have a question I am hoping someone could help with...
I have a variable that contains the content from a webpage (scraped using WWW::Mechanize).
The variable contains data such as these:
$var = "ewrfs sdfdsf cat_dog,horse,rabbit,chicken-pig"
$var = "fdsf iiukui aawwe dffg elephant,MOUSE_RAT,spider,lion-tiger hdsfds jdlkf sdf"
$var = "dsadp poids pewqwe ANTELOPE-GIRAFFE,frOG,fish,crab,kangaROO-KOALA sdfdsf hkew"
The only bits I am interested in from the above examples are:
#array = ("cat_dog","horse","rabbit","chicken-pig")
#array = ("elephant","MOUSE_RAT","spider","lion-tiger")
#array = ("ANTELOPE-GIRAFFE","frOG","fish","crab","kangaROO-KOALA")
The problem I am having:
I am trying to extract only the comma-separated strings from the variables and then store these in an array for use later on.
But what is the best way to make sure that I get the strings at the start (ie cat_dog) and end (ie chicken-pig) of the comma-separated list of animals as they are not prefixed/suffixed with a comma.
Also, as the variables will contain webpage content, it is inevitable that there may also be instances where a commas is immediately succeeded by a space and then another word, as that is the correct method of using commas in paragraphs and sentences...
For example:
Saturn was long thought to be the only ringed planet, however, this is now known not to be the case.
^ ^
| |
note the spaces here and here
I am not interested in any cases where the comma is followed by a space (as shown above).
I am only interested in cases where the comma DOES NOT have a space after it (ie cat_dog,horse,rabbit,chicken-pig)
I have a tried a number of ways of doing this but cannot work out the best way to go about constructing the regular expression.
How about
[^,\s]+(,[^,\s]+)+
which will match one or more characters that are not a space or comma [^,\s]+ followed by a comma and one or more characters that are not a space or comma, one or more times.
Further to comments
To match more than one sequence add the g modifier for global matching.
The following splits each match $& on a , and pushes the results to #matches.
my $str = "sdfds cat_dog,horse,rabbit,chicken-pig then some more pig,duck,goose";
my #matches;
while ($str =~ /[^,\s]+(,[^,\s]+)+/g) {
push(#matches, split(/,/, $&));
}
print join("\n",#matches),"\n";
Though you can probably construct a single regex, a combination of regexs, splits, grep and map looks decently
my #array = map { split /,/ } grep { !/^,/ && !/,$/ && /,/ } split
Going from right to left:
Split the line on spaces (split)
Leave only elements having no comma at the either end but having one inside (grep)
Split each such element into parts (map and split)
That way you can easily change the parts e.g. to eliminate two consecutive commas add && !/,,/ inside grep.
I hope this is clear and suits your needs:
#!/usr/bin/perl
use warnings;
use strict;
my #strs = ("ewrfs sdfdsf cat_dog,horse,rabbit,chicken-pig",
"fdsf iiukui aawwe dffg elephant,MOUSE_RAT,spider,lion-tiger hdsfds jdlkf sdf",
"dsadp poids pewqwe ANTELOPE-GIRAFFE,frOG,fish,crab,kangaROO-KOALA sdfdsf hkew",
"Saturn was long thought to be the only ringed planet, however, this is now known not to be the case.",
"Another sentence, although having commas, should not confuse the regex with this: a,b,c,d");
my $regex = qr/
\s #From your examples, it seems as if every
#comma separated list is preceded by a space.
(
(?:
[^,\s]+ #Now, not a comma or a space for the
#terms of the list
, #followed by a comma
)+
[^,\s]+ #followed by one last term of the list
)
/x;
my #matches = map {
$_ =~ /$regex/;
if ($1) {
my $comma_sep_list = $1;
[split ',', $comma_sep_list];
}
else {
[]
}
} #strs;
$var =~ tr/ //s;
while ($var =~ /(?<!, )\b[^, ]+(?=,\S)|(?<=,)[^, ]+(?=,)|(?<=\S,)[^, ]+\b(?! ,)/g) {
push (#arr, $&);
}
the regular expression matches three cases :
(?<!, )\b[^, ]+(?=,\S) : matches cat_dog
(?<=,)[^, ]+(?=,) : matches horse & rabbit
(?<=\S,)[^, ]+\b(?! ,) : matches chicken-pig
I am looking to do a 2-step regular expression look-up in Perl, I have text that looks like this:
here is some text 9337 more text AA 2214 and some 1190 more BB stuff 8790 words
I also have a hash with the following values:
%my_hash = ( 9337 => 'AA', 2214 => 'BB', 8790 => 'CC' );
Here's what I need to do:
Find a number
Look up the text code for the number using my_hash
Check if the text code appears within 50 characters of the identified number, and if true print the result
So the output I'm looking for is:
Found 9337, matches 'AA'
Found 2214, matches 'BB'
Found 1190, no matches
Found 8790, no matches
Here's what I have so far:
while ( $text =~ /(\d+)(.{1,50})/g ) {
$num = $1;
$text_after_num = $2;
$search_for = $my_hash{$num};
if ( $text_after_num =~ /($search_for)/ ) {
print "Found $num, matches $search_for\n";
}
else {
print "Found $num, no matches\n";
}
This sort of works, except that the only correct match is 9337; the code doesn't match 2214. I think the reason is that the regular expression match on 9337 is including 50 characters after the number for the second-step match, and then when the regex engine starts again it is starting from a point after the 2214. Is there an easy way to fix this? I think the \G modifier can help me here, but I don't quite see how.
Any suggestions or help would be great.
You have a problem with greediness. The 1,50 will consume as much as it can. Your regex should be /(\d+)(.+?)(?=($|\d))/
To explain, the question mark will make the multiple match non-greedy (it will stop as soon as the next pattern is matched - the next pattern gets precedence). The ?= is a lookahead operator to say "check if the next element is a digit. If so, match but do not consume." This allows the first digit to get picked up by the beginning of the regex and be put into the next matched pattern.
[EDIT]
I added an optional end value to the lookahead so that it wouldn't die on the last match.
Just use :
/\b\d+\b/g
Why match everything if you don't need to? You should use other functions to determine where the number is :
/(?=9337.{1,50}AA)/
This will fail if AA is further than 50 chars away from the end of 9337. Of course you will have to interpolate your variables to match your hashe's keys and values. This was just an example for your first key/value pair.