I use regular expressions for sorting data into groups. The lines look somewhat like:
testword test
test testword
tes.w. tes.
tes tes.w.
tes.w othertexttobefound
sometexttobefound testword somemoretextwhichdoesnotmatter
The word test is to be found as well as othertexttobefound and sometexttobefound.
Now I am trying to tell my parser that it is supposed to plainly ignore testword and its derivatives while searching and focus on the rest of my data entries. The "good words" and the "bad words" can be anywhere in each line.
I have tried [^w] which is fine for the beginning of strings, but in my versions not for the other cases. Also (?:w) didn't do the trick. I cannot use lookarounds as these would keep the whole line from being detected.
After long searches on the internet I am hoping for help here!
After much appreciated help from Naxos84, I am adding some German real life examples:
sozialabgabe sozialarbeiter
soz.abg. sozialarbeiter
sozarbeiter soz.abg.
sozialarbeiter otherirrelevantstuff
otherirrelevantstuff soz abg
otherirrelevantstuff sozabg
otherirrelevantstuff sozialabgabe
If I search with:
sozial["^\ab"]|soz["^\ab"]|sometexttobefound|othertexttobefound
Lines 6 and 7 get marked as well, but I don't want those.
What am I doing wrong?
A link:
regexr
To find all the matches you want: any occurence of "test" and "sometexttobefound" and "othertexttobefound you can try the following regex:
test[^\w]|sometexttobefound|othertexttobefound
This regex means:
Find every "test" that is not followed by a word OR sometexttobefound OR othertexttobefound
I tried this regex with the follow text (I added a few 'test's)
testword test
test testword
tes.w. testtes.
tes tes.w. test
tes.w othertexttobefound
sometexttobefound testword somemoretextwhichdoesnotmatter
at regexr (when using the global flag)
If you also want to find things like "tes" I guess you should add it. (I'm not a regex expert)
Like:
test[^\w]|tes[^\w]|sometexttobefound|othertexttobefound
If you want to get all words from the text except from some special words, you could use:
#words = grep{$_ ne 'testword'} split /\P{L}+/, $str;
(if $str is your complete string)
See perl docs for \P{...}. Instead of \P{L}, you could also use \W, but those are locale-dependent.
But if you need to use regexps only, then you could use
#words = $str =~ /\b(?!testword)\p{L}+\b/g;
But again, \b is locale-dependent again, so you might want to use \b{...} or rebuild the word boundary matches with \p{L}:
#words = $str =~ /
(?:(?<=\p{L})(?!\p{L})|(?<!\p{L})(?=\p{L}))
(?!testword)\p{L}+
(?:(?<=\p{L})(?!\p{L})|(?<!\p{L})(?=\p{L}))
/gx;
Related
Working with Windows PowerShell, I am trying to replace all occurrences of a certain word pattern in a big string, by appending a suffix.
$string = "The string that contains several occurrences of ab_abcde, ab_abcde_FOO, ab_vwxyz, ab_vwxyz_BAR, etc"
I want to append the suffix "_XXX" to each one of these matched words in $string
Since I expect all my matches to start with either ab_abcde or ab_vwxyz, I have tried:
$string -replace "(ab_abcde|ab_vwxyz)(.?)\s+", '$1$2_XXX'
and a million other variations, to no avail.
I have spent all day hunting at SO, but haven't found a solution that works well. I would appreciate a little assistance.
PS: Since my $string is actually the output of mysqldump, some of my search words will be wrapped in between grave-accent(`) like so: `ab_abcde`, and I would like to match them. I am not sure how much complexity this might bring, considering that this is also the PowerShell escape character.
Thank you.
Something like
$string -replace "((?:ab_abcde|ab_vwxyz)\w*)", '$1_XXX'
Regex Demo
Like this?
$string = "The string that contains several occurrences of ab_abcde, ab_abcde_FOO, ab_vwxyz, ab_vwxyz_BAR, etc"
$string -replace '(ab_abcde.*?\b|ab_vwxyz.*?\b)', '$1_XXX'
The string that contains several occurrences of ab_abcde_XXX, ab_abcde_FOO_XXX, ab_vwxyz_XXX, ab_vwxyz_BAR_XXX, etc
Edit: updated after additional comments posted.
Here's my example. If I want to use a regex to replace tabs in the code with spaces, but wanted to preserve tab characters in the middle or end of a line of code, I would use this as my search string to capture each tab character at the start of a line: ^(\t)+
Now, how could I write a search string that replaces each captured group with four spaces? I'm thinking there must be some way to do this with backreferences?
I've found I can work around this by running similar regex-replacements (like s/^\t/ /g, s/^ \t/ /g, ...) multiple times until no more matches are found, but I wonder if there's a quicker way to do all the necessary replacements at once.
Note: I used sed format in my example, but I'm not sure if this is possible with sed. I'm wondering if sed supports this, and if not, is there a platform that does? (e.g., there's a Python/Java/bash extended regex lib that supports this.)
With perl and other languages that support this feature (Java, PCRE(PHP, R, libboost), Ruby, Python(the new regex module), .NET), you can use the \G anchor that matches the position after the last match or the start of the string:
s/(?:\G|^)\t/ /gm
This works in Perl. Maybe sed too, I don't know sed.
It relies on doing an eval, basically a callback.
It takes the length of $1 then cats ' ' that many times.
Perl sample.
my $str = "
\t\t\tThree
\t\tTwo
\tOne
None";
$str =~ s/^(\t+)/ ' ' x length($1) /emg;
print "$str\n";
Output
Three
Two
One
None
Just another idea that came to me, this could also be solved with positive lookbehind:
s/(?<=^[\t]*)\t/ /gm
It's ugly, but it works.
sed ':a
s/^\(\t*\)\t/\1 /
ta' YourFile
Use recursive action on 1 regex with sed, it's a workaround
I have this string
asp.net somedomain.com
I need to strip out the domain dot extension part only except in certain cases. So I want this:
asp.net somedomain
Any time there is vb.net, asp.net etc.. I do not want to strip out the extension.
I tried this in perl with no effect.
$company =~ s/(?=\w+)(?!=asp|vb|c#)\.[a-zA-Z]{2,6}\b/\1/g;
My logic is stuff before the dot must be one or more alpha and not asp or vb or c#.
You can use a Negative LookBehind. You were almost there, but using LookAheads.
RegExp: (?<!asp|vb|c\#)\.[a-zA-Z]{2,6}\b
Replace with nothing
Explained demo here: http://regex101.com/r/tG5rO1
To workaround the variable length RegEx error use this: (?<!asp)(?<!vb|c\#)\.[a-z]{2,6}\b
Edit: separate LookBehind group for different length excluded word
This will only find TLD's that don't match your criteria.
Update:
To take care of special cases: don't match words ending in excluded word and match any combination of excluded word (eg. vB VB vb Vb)
RegExp: \b(?<!\b[aA][sS][pP])(?<!\b[vV][bB]|\b[cC]\#)\.[a-zA-Z]{2,6}\b
Explained demo: http://regex101.com/r/bR3kJ8
Or: \b(?<!\basp)(?<!\bvb|\bc\#)\.[a-z]{2,6}\b
When used with case insensitive RegEx modifier i
Update #2
Safer as it cares only about .net TLD and excluded words for it:
/(^|\s)(?!(?:visual)?(?:basic|studio|asp|v[bs]|c\#)\.net)(\w+)(?:\.com?\.[a-z]{2}|\.[a-z]{2,6})\b/\1\2/gi
Needs replacement as opposed with previous variants.
Explained demo: http://regex101.com/r/kL5mQ5
Just match the last one:
my $s = q{asp.net somedomain.com};
my ($company) = ($s =~ / ([A-Za-z]{2,}) [.] (?:[A-Za-z]{2,}) \z /x);
print $company, "\n";
Or, split on space and dot:
my $s = q{asp.net somedomain.com};
my ($company) = split /[.]/, (split ' ', $s)[-1];
print $company, "\n";
How much work you want to put into the pattern depends on how much variation there is in your input. The examples above are based on the sample input your provided.
I'm creating a method to modify page titles into a good string for to use URL rewriting.
Example: "Latest news", would be "latest-news"
The problem is the page titles are out of my control and some are similar to the following:
Football & Rugby News!. Ideally this would become football-rugby-news.
I've done some work to get this to football-&-rugby-news!
Is there a possible regex to identify unwanted characters in there and the extra '-' ?
Basically, I need numbers and letters separated by a single '-'.
I only have basic knowledge of regex, and the best I could come up with was:
[^a-z0-9-]
I'm not sure if I'm being clear enough here.
Try a 'replace all' with something like this.
[^a-zA-Z0-9\\-]+
Replace the matches with a dash.
Alternative regex:
[^a-zA-Z0-9]+
This one will avoid multiple dashes if a dash itself is found near other unwanted characters.
This Perl script also does what you're looking for. Of course you'd have to feed it the string by some other means than just hardcoding it; I merely put it in there for the example.
#!/usr/bin/perl
use strict;
use warnings;
my $string = "Football & Rugby News!";
$string = lc($string); # lowercase
my $allowed = qr/a-z0-9-\s/; # all permitted characters
$string =~ s/[^$allowed]//g; # remove all characters that are NOT in $allowed
$string =~ s/\s+/-/g; # replace all kinds of whitespace with '-'
print "$string\n";
prints
football-rugby-news
being a regex beginner, I need some help writing a regex. It should match a particular pattern, lets say "ABC". But the pattern shouldn't be matched when it is used in comment (' being the comment sign). So XYZ ' ABC
shouldn't match. x("teststring ABC") also shouldn't match. But ABC("teststring ' xxx") has to match to end, that is xxx not being cut off.
Also does anybody know a free Regex application that you can use to "debug" your regex? I often have problems recognizing whats wrong with my tries. Thanks!
Some will swear by RegexBuddy. I've never used the debugger, but I advise you to steer away from the regex generator it provides. It's just a bad idea.
You may be able to pull this off with whatever regex flavor you're using, but in general I think you're going to find it easier and more maintainable to do this the "hard" way. Regular expressions are for regular languages, and nested anything usually means that regexes aren't a good idea. Modern extensions to regex syntax means it may be doable, but it's not going to be pretty, and you sure won't remember what happened in the morning. And one place where regular expressions fail quite spectacularly (even with modern non-regular extensions) is parsing nested structures - trying to parse any mixture comments, quoted strings, and parenthesis quickly devolves into an incomprehensible and unmaintainable mess. Don't get me wrong - I'm a fan of regular expressions in the right places. This isn't one of them.
On the topic of good regex tools, I really like RegexBuddy, but it's not free.
Other than that, a regex is the wrong tool for the job if you need to check inside string delimiters and all sorts too. You need a finite-state machine.
Odd that lots of people recommend their favorite tools, but nobody provides a solution for the problem at hand. (I'm the developer of RegexBuddy, so I'll refrain from recommending any tools.)
There's no good way of matching Y unless it's part of XYZ with a single regular expression. What you can do is write a regex that matches both Y and XYZ: Y|XYZ. Then use a bit of extra code to process the matches for Y, and ignore those for XYZ. One way to do that is with a capturing group: (Y)|XYZ. Now you can process the matches of the first capturing group. When XYZ matches, the capturing group doesn't match anything.
To do this for your VB-style comments, you can use the regex:
'.*|(ABC)
This regex matches a single quote and everything up to the end of the line, or ABC. This regex will match all comments (whether those include ABC or not). The capturing group will match all occurrences of ABC, except those in comments.
If you want your regex to both skip comments and strings, you can add strings to your regex:
'.*|"[^"\r\n]*"|(ABC)
I find the best 'debugger' for regexes is just messing around in an interactive environment trying lots of small bits out. For Python, ipython is great; for Ruby, irb, for command-line type stuff, sed...
Just try out little pieces at a time, make sure you understand them, then add an extra little bit. Rinse and repeat.
For NET development you might as well try RegexDesigner, this tool can generate code(VB/C#) for you. It is a very good tool for us Regex starters.
link text
Here is my solution to this problem:
1. Find a store all your comments in hash
2. Do your regexp replacement
3. Bring comments back to file
Save your time :-)
string fileTextWithComments = "Some tetx file contents";
Dictionary<string, string> comments = new Dictionary<string, string>();
// 1. Find a store all your comments in hash
Regex rc = new Regex("(?:/\\*(?:[^*]|(?:\\*+[^*/]))*\\*+/)|(?://.*)");
MatchCollection matches = rc.Matches(fileTextWithComments);
int index = 0;
foreach (Match match in matches)
{
string key = string.Format("/*Comment#{0}*/", index++);
comments.Add(key, match.Value);
fileTextWithComments = fileTextWithComments.Replace(match.Value, key);
}
// 2. Do your regexp replacement
Regex r = new Regex("YOUR REGEXP PATTERN");
fileTextWithComments = r.Replace(fileTextWithComments, "NEW STRING");
// 3. Bring comments back to file :-)
foreach (string key in comments.Keys)
{
string comment = comments[key];
fileTextWithComments = fileTextWithComments.Replace(key, comment);
}
Could you clarify? I read it thrice, and I think you want to match a given pattern when it appears as a literal. As in not as part of a comment or a string.
What your asking for is pretty tricky to do as a single regexp. Because you want to skip strings. Multiple strings in one line would complicate matters.
I wouldn't even try to do it in one regexp. Instead, I'd pass each line through a filter first, to remove strings, and then comments in that order. And then try and match your pattern.
In Perl because of it's regexp processing power. Assuming #lines is a list of lines you want to match, and $pattern is the pattern you want to match.
#matches =[];
for (#lines){
$line = $_;
$line ~= s/"[^"]*?(?<!\)"//g;
$line ~= s/'.*//g;
push #matches, $_ if $line ~= m/$pattern/;
}
The first substitution finds any pattern that starts with a double quotation mark and ends with the first unescaped double quote. Using the standard escape character of a backspace.
The next strips comments. If the pattern still matches, it adds that line to the list of matches.
It's not perfect because it can't tell the difference between "a\\" and "a\" The first is usually a valid string, the later is not. Either way these substitutions will continue to look for another ", if one isn't found the string isn't thrown out. We could use another substitution to replace all double backslashes with something else. But this will cause problems if the pattern you're looking for contains a backslash.
You can use a zero width look-behind assertion if you only have single line comments, but if you're using multi-line comments, it gets a little trickier.
Ultimately, you really need to solve this kind of issue with some sort of parser, given that the definition of a comment is really driven by a grammar.
This answer to a different but related question looks good too...
If you have Emacs, there is a built-in regex tool called "regexp-builder". I don't really understand the specifics of your regex question well enough to suggest an answer to that.
RegEx1: (-user ")(.*?)"
Subject: report -user "test user" -date 1/4/13 -day monday -daterange "1/4/13 1/20/13" -
Result: -user "test user"
Regex2: (-daterange ")(.*?)"
Subject: report -user "test user" -date 1/4/13 -day monday -daterange "1/4/13 1/20/13" -
Result: -daterange "1/4/13 1/20/13"
RegEx3: (-date )(.*?)( -)
Subject: report -user "test user" -date 1/4/13 -day monday -daterange "1/4/13 1/20/13" -
Result: -date 1/4/13 -
RegEx4: (-day )(.*?)( -)
Subject: report -user "test user" -date 1/4/13 -day monday -daterange "1/4/13 1/20/13" -
Result: -day monday -
Search for the quoted value first if not found, search for the no quotes parameter. This expects only one occurrence of the parameter. It also expects the command to either; use quotes to encapsulate a string with no quotes inside, or; use any character other than a quote in the first position, have no occurrence of ' -' until the next parameter, and have a trailing ' -' (add it onto the string before the regex).