Quite a simple one in theory but can't quite get it!
I want a regex in ant which matches anything as long as it has a slash on the end.
Below is what I expect to work
<regexp id="slash.end.pattern" pattern="*/"/>
However this throws back
java.util.regex.PatternSyntaxException: Dangling meta character '*' near index 0
*/
^
I have also tried escaping this to \*, but that matches a literal *.
Any help appreciated!
Your original regex pattern didn't work because * is a special character in regex that is only used to quantify other characters.
The pattern (.)*/$, which you mentioned in your comment, will match any string of characters not containing newlines, however it uses a possibly unnecessary capturing group. .*/$ should work just as well.
If you need to match newline characters, the dot . won't be enough. You could try something like [\s\S]*/$
On that note, it should be mentioned that you might not want to use $ in this pattern. Suppose you have the following string:
abc/def/
Should this be evaluated as two matches, abc/ and def/? Or is it a single match containing the whole thing? Your current approach creates a single match. If instead you would like to search for strings of characters and then stop the match as soon as a / is found, you could use something like this: [\s\S]*?/.
Related
I want to extract only a specific string if its match
example as an input string:
13.10.0/
13.10.1/
13.10.2/
13.10.3/
13.10.4.2/
13.10.4.4/
13.10.4.5/
I'm using this regex [0-9]+.[0-9]+.[0-9] to extract only digit.digit.digit from a string if its match
but in that case, this is the wrong output related to my regex :
13.10.0
13.10.1
13.10.2
13.10.3
13.10.4.2 (no need to match this string 13.10.4 )
13.10.4.4 (no need to match this string13.10.4 )
13.10.4.5(no need to match this string 13.10.4 )
the correct output that I need :
13.10.0
13.10.1
13.10.2
13.10.3
It's hard to say without knowing how you're passing these strings in -- are they lines in a file? An array of strings in a programming language?
If you're searching a file using grep or a similar tool, it will give you all lines that match anywhere, even if only part of the line matches.
Normally, you'd deal with this using anchors to specify the regex must start on the first character of the line, and end on the last (e.g. ^[0-9]+.[0-9]+.[0-9]$). ^ matches the start of the line, and $ matches at the end.
In your case, you've got slashes at the end of all the lines, so the easiest fix is to match that final slash, with ^[0-9]+.[0-9]+.[0-9]/.
You could also use lookahead or groups to match the slash without returning it -- but that depends a bit more on what tool you're running this regex in and how you're processing it.
If your strings are separated by whitespace (other than newlines), replacing ^ with (^|\s) (either the beginning of the string, or some whitespace character) may work -- but it will add a leading space to some of your results.
You may also need to set your regex tool to match multiple times in a line (e.g. the -o flag in grep). Again, it's hard to give useful advice about this without knowing what regular-expression tool you're using, or how you're processing the results.
I think you want:
^\d+\.\d+\.\d+$
Which is exactly 3 groups of digit(s) separates by (literal) dots.
Some tools (like grep) match all lines that contain your regex, and may have additional characters before/after.
Use $ character to match end of line after your regex. (Also note, that . matches any character, not literal dot)
[0-9]+\.[0-9]+\.[0-9]$
I am trying to regex the following string:
https://www.amazon.com/Tapps-Top-Apps-and-Games/dp/B00VU2BZRO/ref=sr_1_3?ie=UTF8&qid=1527813329&sr=8-3&keywords=poop
I want only B00VU2BZRO.
This substring is always going to be a 10 characters, alphanumeric, preceded by dp/.
So far I have the following regex:
[d][p][\/][0-9B][0-9A-Z]{9}
This matches dp/B00VU2BZRO
I want to match only B00VU2BZRO with no dp/
How do I regex this?
Here is one regex option which would produce an exact match of what you want:
(?<=dp\/)(.*)(?=\/)
Demo
Note that this solution makes no assumptions about the length of the path fragment occurring after dp/. If you want to match a certain number of characters, replace (.*) with (.{10}), for example.
Depending on your language/method of application, you have a couple of options.
Positive look behind. This will make your regex more complicated, but will make it match what you want exactly:
(<=dp/)[0-9A-Z]{10}
The construct (<=...) is called a positive look behind. It will not consume any of the string, but will only allow the match to happen if the pattern between the parens is matched.
Capture group. This will make the regex itself slightly simpler, but will add a step to the extraction process:
dp/([0-9A-Z]{10})
Anything between plain parens is a capture group. The entire pattern will be matched, including dp/, but most languages will give you a way of extracting the portion you are interested in.
Depending on your language, you may need to escape the forward slash (/).
As an aside, you never need to create a character class for single characters: [d][p][\/] can equally well be written as just dp\/.
I'm trying to mass update a web app, I need to create a regex that matches:
lang::id(ALLCHARACTERS]
Can someone assist me with this? I'm not good with regex. I'm pretty sure it can start like:
lang\:\:\(WHAT GOES HERE\]
Something like this would work:
lang::id\([^]]*]
This will match a literal lang::id\(, followed by zero or more of any character other than ], followed by a literal ].
Note that the only character that really needs to be escaped is the open parenthesis.
lang::id\(.*]
The . means any single character, and then * repeats it zero->N times. Make sure to escape the ( since it is used inside regex and is a special char for them, so escaping it with \ is needed, or the regex will probably complain about unbalanced parenthesis.
If you wanted it to not include all characters, you can add a smaller regex in place of the .*. This way you can break the regex down into smaller chunks which help make it easier to understand and develop for some complex rules.
I'm sure this is a simple question for someone at ease with regular expressions:
I need to match everything up until the character #
I don't want the string following the # character, just the stuff before it, and the character itself should not be matched. This is the most important part, and what I'm mainly asking. As a second question, I would also like to know how to match the rest, after the # character. But not in the same expression, because I will need that in another context.
Here's an example string:
topics/install.xml#id_install
I want only topics/install.xml. And for the second question (separate expression) I want id_install
First expression:
^([^#]*)
Second expression:
#(.*)$
[a-zA-Z0-9]*[\#]
If your string contains any other special characters you need to add them into the first square bracket escaped.
I don't use C#, but i will assume that it uses pcre... if so,
"([^#]*)#.*"
with a call to 'match'. A call to 'search' does not need the trailing ".*"
The parens define the 'keep group'; the [^#] means any character that is not a '#'
You probably tried something like
"(.*)#.*"
and found that it fails when multiple '#' signs are present (keeping the leading '#'s)?
That is because ".*" is greedy, and will match as much as it can.
Your matcher should have a method that looks something like 'group(...)'. Most matchers
return the entire matched sequence as group(0), the first paren-matched group as group(1),
and so forth.
PCRE is so important i strongly encourage you to search for it on google, learn it, and always have it in your programming toolkit.
Use look ahead and look behind:
To get all characters up to, but not including the pound (#): .*?(?=\#)
To get all characters following, but not including the pound (#): (?<=\#).*
If you don't mind using groups, you can do it all in one shot:
(.*?)\#(.*) Your answers will be in group(1) and group(2). Notice the non-greedy construct, *?, which will attempt to match as little as possible instead of as much as possible.
If you want to allow for missing # section, use ([^\#]*)(?:\#(.*))?. It uses a non-collecting group to test the second half, and if it finds it, returns everything after the pound.
Honestly though, for you situation, it is probably easier to use the Split method provided in String.
More on lookahead and lookbehind
first:
/[^\#]*(?=\#)/ edit: is faster than /.*?(?=\#)/
second:
/(?<=\#).*/
For something like this in C# I would usually skip the regular expressions stuff altogether and do something like:
string[] split = exampleString.Split('#');
string firstString = split[0];
string secondString = split[1];
For a text file, I want to match to the string that starts with "BEAM" and "FILE PATH". I would have used
^BEAM.*$
^FILE PATH.*$
if I were to match them separately. But now I have to concatenate those two matching patterns into one pattern.
Any idea on how to do this?
A pipe/bar character generally represents "or" with regexps. You could try:
^(BEAM|FILE PATH).*$
The accepted answer is right but you may have redundancy in your Regular Expression.
^ means match the start of a line
(BEAM|FILE PATH) - means the string "BEAM" or the string "FILE PATH"
.* means anything at all
$ means match the end of the line
So in effect, all you are saying is match my strings at the beginning of the line since you don't care what's at the end. You could do this with:
^(BEAM|FILE PATH)
There are two cases where this reduction wouldn't be valid:
If you doing some with the matched string, so you want to match the whole line to pass the data to something else.
You're using a Regular Expression function that wants to match a whole string rather than part of it. You can sometimes solve this by picking the a different Regular Expression function or method. For example in Python use search instead of match.
If the above post doesn't work, try escaping the () and | in different ways until you find one that works. Some regex engines treat these characters differently (special vs. non-special characters), especially if you are running the match in a shell (shell will look for special characters too):
^\(BEAM|FILE PATH\).*$
%\(BEAM\|FILE PATH\).*$
etc.