Perl greedy regexp - regex
I have the following string:
$foo = "'fdsfdsf', 'fsdfdsfdsfdsfds fdsf sdfd f sfs', 'fsdfsdfsd f' fdfsdfdsfdsfsf";
I want to get everything between ' ' but from first to last occurrence.
I have tried to search my string by /.*('.*').*/ but only 'fdsfdsf' was taken, how to turn on greedy or something like that?
* is greedy (*? is the non-greedy version). The following regex works fine: /'(.*)'/.
I am going to go out on a limb and assume that you want to actually get each everything between single quotes within each comma-separated field.
#!/usr/bin/perl
use strict; use warnings;
my $foo = "'fdsfdsf', 'fsdfdsfdsfdsfds fdsf sdfd f sfs', 'fsdfsdfsd f' fdfsdfdsfdsfsf";
my #fields = map /'([^']*)'/, split ', ', $foo;
use YAML;
print Dump \#fields;
Output:
---
- fdsfdsf
- fsdfdsfdsfdsfds fdsf sdfd f sfs
- fsdfsdfsd f
Try
#result = $subject =~ m/'([^']*)'/g;
This will give you the strings enclosed in single quotes within each field in the string.
Of course, the quotes need to be balanced, and the regex match will be thrown off by escaped quotes in your string, so if those may occur, the pattern needs to be modified.
For example,
m/'((?:\\.|[^'])*)'/
would work if quotes can be escaped with backlashes.
Below seems to be working as well. Please check:
#res = $str =~ m/'([A-Z|a-z| ]*)'*/g;
Related
Perl regular expression to get 'This text':(
for example , if i have 'Sample text':( My $1 should be Sample text, so any string which is enclosed in ' ' and is before :(
The following will do the trick:
/'([^']*)':\(/
For example,
my $str = "'Sample text':(";
my ($match) = $str =~ /'([^']*)':\(/
or die("No match\n");
say $match; # Sample text
Here is the simplest code to answer the question:
#/usr/bin/perl
use strict;
"'Sample text':(" =~ /'(.*)':\(/;
print "$1\n"
I'm not adding anything new here but just some samples and a place for you to test it yourself and see perhaps how it works. There are two assumptions here: No escape characters, such as 'Sam\'ple text'. :( is directly after your string. If it's not, you'd want to do a lookahead instead. + requires at least one character in your string. So 'a':( would be valid but '':( would not. If you want to allow empty strings, use * instead of +. '([^']+)':\(
perl regex partial word match
I am trying to remove all words that contain two keys (in Perl). For example, the string garble variable10 variable1 vssx vddx xi_21_vssx vddx_garble_21 xi_blahvssx_grbl_2 Should become garble variable10 variable1 To just remove the normal, unappended/prepended keys is easy: $var =~ s/(vssx|vddx)/ /g; However I cannot figure out how to get it to remove the entire xi_21_vssx part. I tried: $var =~ s/\s.*(vssx|vddx).*\s/ /g Which does not work correctly. I do not understand why... it seems like \s should match the space, then .* matches anything up to one of the patterns, then the pattern, then .* matches anything preceding the pattern until the next space. I also tried replacing \s (whitespace) with \b (word boundary) but it also did it work. Another attempt: $var =~ s/ .*(vssx|vddx).* / /g $var =~ s/(\s.*vssx.*\s|\s.*vddx.*\s)/ /g As well as a few other mungings. Any pointers/help would be greatly appreciated. -John
I think the regex will just be $var =~ s/\S*(vssx|vddx)\S*/ /g;
You can use \s*\S*(?:vssx|vddx)\S*\s* The problem with your regex were: The .* should have been non-greedy. The .* in front of (vssx|vddx) mustn't match whitespace characters, so you have to use \S*. Note that there's no way to properly preserve the space between words - i.e. a vssx b will become ab. regex101 demo.
I am trying to remove all words that [...]
This type of problem lends itself well to grep, which can be used to find the elements in a list that match a condition. You can use split to convert your string to a list of words and then filter it like this:
use strict;
use warnings;
use 5.010;
my $string = 'garble variable10 variable1 vssx vddx xi_21_vssx vddx_garble_21 xi_blahvssx_grbl_2';
my #words = split ' ', $string;
my #filtered = grep { $_ !~ /(?:vssx|vddx)/ } #words;
say "#filtered";
Output:
garble variable10 variable1
Try this as the regex: \b[\w]*(vssx|vddx)[\w]*\b
Match string in Perl with space or with no-space in it
$search_buffer="this text has teststring in it, it has a Test String too";
#waitfor=('Test string','some other string');
foreach my $test (#waitfor)
{
eval ('if (lc $search_buffer =~ lc ' . $test . ') ' .
'{' .
' $prematch = $`;' .
' $match = $&; ' .
' $postmatch = ' . "\$';" .
'}');
print "prematch=$prematch\n";
print "match=$match\n"; #I want to match both "teststring" and "Test String"
print "postmatch=$postmatch\n";
}
I need to print both teststring and Test String, can you please help? thanks.
my $search_buffer="this text has teststring in it, it has a Test String too"; my $pattern = qr/test ?string/i; say "Match found: $1" while $search_buffer =~ /($pattern)/g;
That is a horrible piece of code you have there. Why are you using eval and trying to concatenate strings into code, remembering to interpolate some variables and forgetting about some? There is no reason to use eval in that situation at all.
I assume that you by using lc are trying to make the match case-insensitive. This is best done by using the /i modifier on your regex:
$search_buffer =~ /$test/i; # case insensitive match
In your case, you are trying to match some strings against another string, and you want to compensate for case and for possible whitespace inside. I assume that your strings are generated in some way, and not hard coded.
What you could do is simply to make use of the /x modifier, which will make literal whitespace inside your regex ignored.
Something that you should take into consideration is meta characters inside your strings. If you for example have a string such as foo?, the meta character ? will alter the meaning of your regex. You can disable meta characters inside a regex with the \Q ... \E escape sequence.
So the solution is
use strict;
use warnings;
use feature 'say';
my $s = "this text has teststring in it, it has a Test String too";
my #waitfor= ('Test string','some other string', '#test string');
for my $str (#waitfor) {
if ($s =~ /\Q$str/xi) {
say "prematch = $`";
say "match = $&";
say "postmatch = $'";
}
}
Output:
prematch = this text has teststring in it, it has a
match = Test String
postmatch = too
Note that I use
use strict;
use warnings;
These two pragmas are vital to learning how to write good Perl code, and there is no (valid) reason you should ever write code without them.
This would work for your specific example. test\s?string Basically it marks the space as optional [\s]?. The problem that I'm seeing with this is that it requires you to know where exactly there might be a space inside the string you're searching. Note: You might also have to use the case-insensitive flag which would be /Test[\s]?String/i
Text replacement with backslash in a variable in Perl
How can I replace the backslash inside the variable? $string = 'a\cc\ee'; $re = 'a\\cc'; $rep = "Work"; #doesnt work in variable $string =~ s/$re/$rep/og; print $string."\n"; #work with String $string =~ s/a\\cc/$rep/og; print $string."\n"; output: a\cc\ee Work\ee
Because you're using this inside of a regex -- you probably want quotemeta() or \Q and \E (see perldoc perlre) perl -E'say quotemeta( q[a/asf$## , d] )' # prints: a\/asf\$\#\#\ \,\ d # Or, with `\Q`, and `\E` $string =~ s/\Q$re\E/$rep/og; print $string."\n";
If you set $re = 'a\cc';, it would work. The backslash is not getting interpolated as you expect when you include it in the regex as a variable: it is being used literally in the substitution. Alternatively you could define the string with double quotes, but that's not a good practice. It's better to always use single quotes in your strings unless you explicitly want to interpolate something in the content -- it saves an infitesimal amount of processing, but it is a hint to the reader as to what you the programmer intended.
The problem is that you're using single quotes to define $re. That means that when you use it in the search pattern it looks for two slashes. Single quotes tell Perl not to interpolate the strings, but to use the raw characters instead. Each slash is taken literally and as an escape. Compare: $re0 = 'a\\cc'; $re1 = "a\\cc"; When you print them out you'll see: print $re0."\n".$re1."\n"; a\\cc a\cc On the other hand, when you use the string directly in the regex, it's interpolated, so you need one slash to act as an escape, and another to be what you're escaping.
How do I use Perl to intersperse characters between consecutive matches with a regex substitution?
The following lines of comma-separated values contains several consecutive empty fields: $rawData = "2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,Clear\n 2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,,,\n" I want to replace these empty fields with 'N/A' values, which is why I decided to do it via a regex substitution. I tried this first of all: $rawdata =~ s/,([,\n])/,N\/A/g; # RELABEL UNAVAILABLE DATA AS 'N/A' which returned 2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,N/A,Clear\n 2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,N/A,,N/A,\n Not what I wanted. The problem occurs when more than two consecutive commas occur. The regex gobbles up two commas at a time, so it starts at the third comma rather than the second when it rescans the string. I thought this could be something to do with lookahead vs. lookback assertions, so I tried the following regex out: $rawdata =~ s/(?<=,)([,\n])|,([,\n])$/,N\/A$1/g; # RELABEL UNAVAILABLE DATA AS 'N/A' which resulted in: 2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,N/A,Clear\n 2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,N/A,,N/A,,N/A,,N/A\n That didn't work either. It just shifted the comma-pairings by one. I know that washing this string through the same regex twice will do it, but that seems crude. Surely, there must be a way to get a single regex substitution to do the job. Any suggestions? The final string should look like this: 2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,N/A,N/A,Clear\n 2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,N/A,,N/A,N/A,N/A,N/A,N/A\n
EDIT: Note that you could open a filehandle to the data string and let readline deal with line endings:
#!/usr/bin/perl
use strict; use warnings;
use autodie;
my $str = <<EO_DATA;
2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,Clear
2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,,,
EO_DATA
open my $str_h, '<', \$str;
while(my $row = <$str_h>) {
chomp $row;
print join(',',
map { length $_ ? $_ : 'N/A'} split /,/, $row, -1
), "\n";
}
Output:
E:\Home> t.pl
2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,N/A,Clear
2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,N/A,N/A,N/A,N/A
You can also use:
pos $str -= 1 while $str =~ s{,(,|\n)}{,N/A$1}g;
Explanation: When s/// finds a ,, and replaces it with ,N/A, it has already moved to the character after the last comma. So, it will miss some consecutive commas if you only use
$str =~ s{,(,|\n)}{,N/A$1}g;
Therefore, I used a loop to move pos $str back by a character after each successful substitution.
Now, as #ysth shows:
$str =~ s!,(?=[,\n])!,N/A!g;
would make the while unnecessary.
I couldn't quite make out what you were trying to do in your lookbehind example, but I suspect you are suffering from a precedence error there, and that everything after the lookbehind should be enclosed in a (?: ... ) so the | doesn't avoid doing the lookbehind. Starting from scratch, what you are trying to do sounds pretty simple: place N/A after a comma if it is followed by another comma or a newline: s!,(?=[,\n])!,N/A!g; Example: my $rawData = "2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,Clear\n2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,,,\n"; use Data::Dumper; $Data::Dumper::Useqq = $Data::Dumper::Terse = 1; print Dumper($rawData); $rawData =~ s!,(?=[,\n])!,N/A!g; print Dumper($rawData); Output: "2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,Clear\n2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,,,\n" "2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,N/A,Clear\n2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,N/A,N/A,N/A,N/A\n"
You could search for (?<=,)(?=,|$) and replace that with N/A. This regex matches the (empty) space between two commas or between a comma and end of line.
The quick and dirty hack version:
my $rawData = "2008-02-06,8:00 AM,14.0,6.0,59,1027,-9999.0,West,6.9,-,N/A,,Clear
2008-02-06,9:00 AM,16,6,40,1028,12,WNW,10.4,,,,\n";
while ($rawData =~ s/,,/,N\/A,/g) {};
print $rawData;
Not the fastest code, but the shortest. It should loop through at max twice.
Not a regex, but not too complicated either:
$string = join ",", map{$_ eq "" ? "N/A" : $_} split (/,/, $string,-1);
The ,-1 is needed at the end to force split to include any empty fields at the end of the string.