I have been pondering on this for quite awhile and still can't figure it out. The regex look ahead/behinds. Anyway, I'm not sure which to use in my situation, I am still having trouble grasping the concept. Let me give you an example.
I have a name....My Business,LLC (Milwaukee,WI)_12345678_12345678
What I want to do is if there is a comma in the name, no matter how many, remove it. At the same time, if there is not a comma in the name, still read the line. The one-liner I have is listed below.
s/(.*?)(_)(\d+_)(\d+$)/$1$2$3$4/gi;
I want to remove any comma from $1(My Business,LLC (Milwaukee,WI)). I could call out the comma in regex as a literal string((.?),(.?),(.*?)(_.*?$)) if it was this EXACT situation everytime, however it is not.
I want it to omit commas and match 'My Business, LLC_12345678_12345678' or just 'My Business_12345678_12345678', even though there is no comma.
In any situation I want it to match the line, comma or not, and remove any commas(if any) no matter how many or where.
If someone can help me understand this concept, it will be a breakthrough!!
Use the /e modifier of Perl so that you can pass your function during the replace in s///
$str = 'My Business,LLC (Milwaukee,WI)_12345678_12345678';
## modified your regex as well using lookahead
$str =~ s/(.*?)(?=_\d+_\d+$)/funct($1)/ge;
print $str;
sub funct{
my $val = shift;
## replacing , with empty, use anything what you want!
$val =~ s/,//g;
return $val;
}
Using funct($1) in substitute you are basically calling the funct() function with parameter $1
Related
I have a string coming in from raw data. I can't guarantee that there might or might not be an extra comma. I thought I might be able to remove it like this:
$value = "cat, dog, fish, ";
$value =~ s/,//r;
Sadly that doesn't work. Of course I could do a loop to check the last char of the string one by one, but I would like to learn how to do it with the Regex backslash method.
Can someone help me please?
Try this
$value =~ s/,\s*$//;
The pattern ,\s*$ matches a comma (,) followed by zero or more space-chars (\s*), followed by the end of the line/input ($).
s/,// removes the first comma. So,
$value = reverse(reverse($value) =~ s/,//r);
Not sure why you are specifying /r in your code but not using the return value. If in fact you are using it, add it back.
s/.*\K,//
Ah, if there may not be a trailing comma that you don't want, this won't work; it will always delete the last comma. Use Bart's answer then.
The accepted answer removes a comma followed by zero or more white space characters at the end of a string. But you asked about removing the last comma. Either is consistent with your example, but if you really want to remove the last comma, one way is:
$value =~ s/,([^,]*$)/$1/
This will, for example, change "foo,bar,baz" to "foo,barbaz", and in your example"cat, dog, fish, "to"cat, dog, fish "` (leaving the trailing space).
The reverse trick in choruba's answer also works.
If nothing else, this shows the importance of a precise problem statement.
Using positive look ahead,
$value =~ s/,(?=[^,]*\z)//;
I suggest this pattern: ,*\s*$. It matches all commas (if any) and all white spaces (if any) and the end of the string.
A full example:
use 5.18.2;
use strict ;
use warnings ;
use Data::Dumper;
my $data = "cat, dog, fish,,,,,,,,,,,,, ";
$data =~ s/,*\s*$// ;
print $data;
I have this code in perl where I want to extract the value of 'EUR_AF', in this case '0.39'.
Sometimes 'EUR_AF' ends with ';', sometimes it doesn't.
Alternatively, 'EUR_AF' may end with '=0' instead of '=0.39;' or '=0.39'.
How do I make the code handle that? Can't seem to find it online...I could of course wrap everything in an almost endless if-elsif-else statement, but that seems overkill.
Example text:
AVGPOST=0.9092;AN=2184;RSQ=0.5988;ERATE=0.0081;AC=144;VT=SNP;THETA=0.0045;AA=A;SNPSOURCE=LOWCOV;LDAF=0.0959;AF=0.07;ASN_AF=0.05;AMR_AF=0.10;AFR_AF=0.11;EUR_AF=0.039
Code: $INFO =~ m/\;EUR\_AF\=(.*?)(;)/
I did find that: $INFO =~ m/\;EUR\_AF\=(.*?0)/ handles the cases of EUR_AF=0, but how to handle alternative scenarios efficiently?
Extract one value:
my ($eur_af) = $s =~ /(?:^|;)EUR_AF=([^;]*)/;
my ($eur_af) = ";$s" =~ /;EUR_AF=([^;]*)/;
Extract all values:
my %rec = split(/[=;]/, $s);
my $eur_af = $rec{EUR_AF};
This regex should work for you: (?<=EUR_AF=)\d+(\.\d+)?
It means
(?<=EUR_AF=) - look for a string preceeded by EUR_AF=
\d+(\.\d+)? - consist of a digit, optionally a decimal digit
EDIT: I originally wanted the whole regex to return the correct result, not only the capture group. If you want the correct capture group edit it to (?<=EUR_AF=)(\d+(?:\.\d+)?)
I have found the answer. The code:
$INFO =~ m/(?:^|;)EUR_AF=([^;]*)/
seems to handle the cases where EUR_AF=0 and EUR_AF=0.39, ending with or without ;. The resulting $INFO will be 0 or 0.39.
How would I go about removing all characters before a "_" in perl? So if I had a string that was "124312412_hithere" it would replace the string as just "hithere". I imagine there is a very simple way to do this using regex, but I am still new dealing with that so I need help here.
Remove all characters up to and including "_":
s/^[^_]*_//;
Remove all characters before "_":
s/^[^_]*(?=_)//;
Remove all characters before "_" (assuming the presence of a "_"):
s/^[^_]*//;
This is a bit more verbose than it needs to be, but would be probably more valuable for you to see what's going on:
my $astring = "124312412_hithere";
my $find = "^[^_]*_";
my $replace = "_";
$astring =~ s/$find/$replace/;
print $astring;
Also, there's a bit of conflicting requirements in your question. If you just want hithere (without the leading _), then change it to:
$astring =~ s/$find//;
I know it's slightly different than what was asked, but in cases like this (where you KNOW the character you are looking for exists in the string) I prefer to use split:
$str = '124312412_hithere';
$str = (split (/_/, $str, 2))[1];
Here I am splitting the string into parts, using the '_' as a delimiter, but to a maximum of 2 parts. Then, I am assigning the second part back to $str.
There's still a regex in this solution (the /_/) but I think this is a much simpler solution to read and understand than regexes full of character classes, conditional matches, etc.
You can try out this: -
$_ = "124312412_hithere";
s/^[^_]*_//;
print $_; # hithere
Note that this will also remove the _(as I infer from your sample output). If you want to keep the _ (as it seems doubtful what you want as per your first statement), you would probably need to use look-ahead as in #ikegami's answer.
Also, just to make it little more clear, any substitution and matching in regex is applied by default on $_. So, you don't need to bind it to $_ explicitly. That is implied.
So, s/^[^_]*_//; is essentially same as - $_ =~ s/^[^_]*_//;, but later one is not really required.
I think this question is repeated, but searching wasn't helpful for me.
my $pattern = "javascript:window.open\('([^']+)'\);";
$mech->content =~ m/($pattern)/;
print $1;
I want to have an external $pattern in the regular expression. How can I do this? The current one returns:
Use of uninitialized value $1 in print at main.pm line 20.
$1 was empty, so the match did not succeed. I'll make up a constant string in my example of which I know that it will match the pattern.
Declare your regular expression with qr, not as a simple string. Also, you're capturing twice, once in $pattern for the open call's parentheses, once in the m operator for the whole thing, therefore you get two results. Instead of $1, $2 etc. I prefer to assign the results to an array.
my $pattern = qr"javascript:window.open\('([^']+)'\);";
my $content = "javascript:window.open('something');";
my #results = $content =~ m/($pattern)/;
# expression return array
# (
# q{javascript:window.open('something');'},
# 'something'
# )
When I compile that string into a regex, like so:
my $pattern = "javascript:window.open\('([^']+)'\);";
my $regex = qr/$pattern/;
I get just what I think I should get, following regex:
(?-xism:javascript:window.open('([^']+)');)/
Notice that it it is looking for a capture group and not an open paren at the end of 'open'. And in that capture group, the first thing it expects is a single quote. So it will match
javascript:window.open'fum';
but not
javascript:window.open('fum');
One thing you have to learn, is that in Perl, "\(" is the same thing as "(" you're just telling Perl that you want a literal '(' in the string. In order to get lasting escapes, you need to double them.
my $pattern = "javascript:window.open\\('([^']+)'\\);";
my $regex = qr/$pattern/;
Actually preserves the literal ( and yields:
(?-xism:javascript:window.open\('([^']+)'\);)
Which is what I think you want.
As for your question, you should always test the results of a match before using it.
if ( $mech->content =~ m/($pattern)/ ) {
print $1;
}
makes much more sense. And if you want to see it regardless, then it's already implicit in that idea that it might not have a value. i.e., you might not have matched anything. In that case it's best to put alternatives
$mech->content =~ m/($pattern)/;
print $1 || 'UNDEF!';
However, I prefer to grab my captures in the same statement, like so:
my ( $open_arg ) = $mech->content =~ m/($pattern)/;
print $open_arg || 'UNDEF!';
The parens around $open_arg puts the match into a "list context" and returns the captures in a list. Here I'm only expecting one value, so that's all I'm providing for.
Finally, one of the root causes of your problems is that you do not need to specify your expression in a string in order for your regex to be "portable". You can get perl to pre-compile your expression. That way, you only care what instructions the characters are to a regex and not whether or not you'll save your escapes until it is compiled into an expression.
A compiled regex will interpolate itself into other regexes properly. Thus, you get a portable expression that interpolates just as well as a string--and specifically correctly handles instructions that could be lost in a string.
my $pattern = qr/javascript:window.open\('([^']+)'\);/;
Is all that you need. Then you can use it, just as you did. Although, putting parens around the whole thing, would return the whole matched expression (and not just what's between the quotes).
You do not need the parentheses in the match pattern. It will match the whole pattern and return that as $1, which I am guess is not matching, but I am only guessing.
$mech->content =~ m/$pattern/;
or
$mech->content =~ m/(?:$pattern)/;
These are the clustering, non-capturing parentheses.
The way you are doing it is correct.
The solutions have been already given, I'd like to point out that the window.open call might have multiple parameters included in "" and grouped by comma like:
javascript:window.open("http://www.javascript-coder.com","mywindow","status=1,toolbar=1");
There might be spaces between the function name and parentheses, so I'd use a slighty different regex for that:
my $pattern = qr{
javascript:window.open\s*
\(
([^)]+)
\)
}x;
print $1 if $text =~ /$pattern/;
Now you have all parameters in $1 and can process them afterwards with split /,/, $stuff and so on.
It reports an uninitialized value because $1 is undefined. $1 is undefined because you have created a nested matching group by wrapping a second set of parentheses around the pattern. It will also be undefined if nothing matches your pattern.
I'm really getting my butt kicked here. I can not figure out how to write a search and replace that will properly find this string.
String:
$QData{"OrigFrom"} $Text{"wrote"}:
Note: That is the actual STRING. Those are NOT variables. I didn't write it.
I need to replace that string with nothing. I've tried escaping the $, {, and }. I've tried all kinds of combinations but it just can't get it right.
Someone out there feel like taking a stab at it?
Thanks!
No one likes quotemeta? Let Perl figure it out so you don't strain you eyes with all those backslashes. :)
my $string = 'abc $QData{"OrigFrom"} $Text{"wrote"}: def';
my $escaped = quotemeta '$QData{"OrigFrom"} $Text{"wrote"}:';
$string =~ s/$escaped/Ponies!/;
print $string;
I originally thought that wrapping your regex in \Q/\E (the quotemeta start and end escapes) would be all that you needed to do, but it turns out that $ (and #) are not
allowed inside \Q...\E sequences (see http://search.cpan.org/perldoc/perlre#Escape_sequences).
So what you need to do is escape the $ characters separately, but you can wrap everything else in \Q ... \E:
/\$\QQData{"OrigFrom"} \E\$\QText{"wrote"}:\E/
regex using escape character \ would be
s/\$QData\{"OrigFrom"\} \$Text\{"wrote"\}://;
full test code:
#!/sw/bin/perl
$_='$QData{"OrigFrom"} $Text{"wrote"}:';
s/\$QData\{"OrigFrom"\} \$Text\{"wrote"\}://;
print $_."\n";
outputs nothing but newline.