regex - w3toppers.com

What is “The Best” U.S. Currency RegEx?

here’s some stuff from the makers of Regex Buddy. These came from the library so i’m confident they have been thoroughly tested. Number: Currency amount (cents mandatory) Optional thousands separators; mandatory two-digit fraction Match; JGsoft: ^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*\.[0-9]{2}$ Number: Currency amount (cents optional) Optional thousands separators; optional two-digit fraction Match; JGsoft: ^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*(?:\.[0-9]{2})?$ Number: Currency amount US & … Read more

Extract a regular expression match

Use the new stringr package which wraps all the existing regular expression operates in a consistent syntax and adds a few that are missing: library(stringr) str_locate(“aaa12xxx”, “[0-9]+”) # start end # [1,] 4 5 str_extract(“aaa12xxx”, “[0-9]+”) # [1] “12”

(grep) Regex to match non-ASCII characters?

This will match a single non-ASCII character: [^\x00-\x7F] This is a valid PCRE (Perl-Compatible Regular Expression). You can also use the POSIX shorthands: [[:ascii:]] – matches a single ASCII char [^[:ascii:]] – matches a single non-ASCII char [^[:print:]] will probably suffice for you.**

Negative matching using grep (match lines that do not contain foo)

grep -v is your friend: grep –help | grep invert -v, –invert-match select non-matching lines Also check out the related -L (the complement of -l). -L, –files-without-match only print FILE names containing no match

Escape function for regular expression or LIKE patterns

To address the question at the top: Assuming standard_conforming_strings = on, like it’s default since Postgres 9.1. Regular expression escape function Let’s start with a complete list of characters with special meaning in regular expression patterns: !$()*+.:<=>?[\]^{|}- Wrapped in a bracket expression most of them lose their special meaning – with a few exceptions: – … Read more

Random string that matches a regexp [duplicate]

Welp, just musing, but the general question of generating random inputs that match a regex sounds doable to me for a sufficiently relaxed definition of random and a sufficiently tight definition of regex. I’m thinking of the classical formal definition, which allows only ()|* and alphabet characters. Regular expressions can be mapped to formal machines … Read more

MongoDB Regex Search on Integer Value

If you are wanting to do a pattern match on numbers, the way to do it in mongo is use the $where expression and pass in a pattern match. > db.test.find({ $where: “/^123.*/.test(this.example)” }) { “_id” : ObjectId(“4bfc3187fec861325f34b132”), “example” : 1234 }

How do I use regular expressions in bash scripts?

It was changed between 3.1 and 3.2: This is a terse description of the new features added to bash-3.2 since the release of bash-3.1. Quoting the string argument to the [[ command’s =~ operator now forces string matching, as with the other pattern-matching operators. So use it without the quotes thus: i=”test” if [[ $i … Read more

Regular expression negative lookahead

A negative lookahead says, at this position, the following regex can not match. Let’s take a simplified example: a(?!b(?!c)) a Match: (?!b) succeeds ac Match: (?!b) succeeds ab No match: (?!b(?!c)) fails abe No match: (?!b(?!c)) fails abc Match: (?!b(?!c)) succeeds The last example is a double negation: it allows b followed by c. The … Read more

A Regex that will never be matched by anything

Leverage negative lookahead: >>> import re >>> x=r'(?!x)x’ >>> r=re.compile(x) >>> r.match(”) >>> r.match(‘x’) >>> r.match(‘y’) this RE is a contradiction in terms and therefore will never match anything. NOTE: In Python, re.match() implicitly adds a beginning-of-string anchor (\A) to the start of the regular expression. This anchor is important for performance: without it, the … Read more