Regex testing for special characters, decimal except for hyphen, commas, alpha-numeric. Attempt ^(\+|-)?([0-9]+)$/  I'm trying to write a regex to match special characters, decimal except for commas, a hyphen, alpha-numeric.
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I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?
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#!/bin/bash INT=-5  if [[ "$INT" =~ ^-?[0-9]+$ ]]; then  echo "INT is an integer."  else  echo "INT is not an integer." &gt;&amp;2  exit 1  fi   What does the leading ~ do in the starting regular expression?
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What is the best possible way to check if a string can be represented as a number in Python?   The function I currently have right now is:  def is_number(s):     try:         float(s)         return True     except ValueError:         return False   Which, not only is ugly and slow, seems clunky. However I haven't found a better method because calling float in the main function is even worse.
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Does Java have a built-in way to escape arbitrary text so that it can be included in a regular expression? For example, if my users enter "$5", I'd like to match that exactly rather than a "5" after the end of input.
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Is it possible to detect a valid regular expression with another regular expression?  If so please give example code below.
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I've been retagging posts matching [special] -character -[character] is:question  The sidebar gives this helpful description of my query:     results found not containing   and not containing   tagged with       not       search options   questions only   It looks like there are some words missing there...
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I'm trying to get a regex that will match:  somefile_1.txt somefile_2.txt somefile_{anything}.txt   but not match:  somefile_16.txt   I tried  somefile_[^(16)].txt   with no luck (it includes even the "16" record)
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I was writing some Unit tests last week for a piece of code that generated some SQL statements.  I was trying to figure out a regex to match SELECT, INSERT and UPDATE syntax so I could verify that my methods were generating valid SQL, and after 3-4 hours of searching and messing around with various regex editors I gave up.  I managed to get partial matches but because a section in quotes can contain any characters it quickly expands to match the whole statement.  Any help would be appreciated, I'm not very good with regular expressions but I'd like to learn more about them.  By the way it's C# RegEx that I'm after.  Clarification  I don't want to need access to a database as this is part of a Unit test and I don't wan't to have to maintain a database to test my code. which may live longer than the project.
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Assume I have created a compiled re:  x = re.compile('^\d+$')   Is there a way to extract the pattern string (^\d+$) back from the x?
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Why do PHP regexes have the surrounding delimiters? It seems like it would be more clear if any pattern modifiers were passed in as a parameter to whatever function was being used.
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What is the most efficient way of testing an input string whether it contains a numeric value (or conversely Not A Number)? I guess I can use Double.Parse or a regex (see below) but I was wondering if there is some built in way to do this, such as javascript's NaN() or IsNumeric() (was that VB, I can't remember?).  public static bool IsNumeric(this string value) {     return Regex.IsMatch(value, "^\\d+$"); }
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I want to check if a variable has a valid year using a regular expression. Reading the  I understand I could use the operator =~  Looking at the example below, I would expect to see "not OK" but I see "OK". What am I doing wrong?  i="test" if [ $i=~"200[78]" ] then   echo "OK" else   echo "not OK" fi
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I'm trying to format numbers. Examples:  1     =&gt; 1 12    =&gt; 12 123   =&gt; 123 1234  =&gt; 1,234 12345 =&gt; 12,345   It strikes as a fairly common thing to do but I can't figure out which filter I'm supposed to use.  Edit: If you've a generic Python way to do this, I'm happy adding a formatted field in my model.
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What is the easiest way to match non-ASCII characters in a regex? I would like to match all words individually in an input string, but the language may not be English, so I will need to match things like ü, ö, ß, and ñ. Also, this is in Javascript/jQuery, so any solution will need to apply to that.
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What mysql functions are there (if any) to trim leading zeros from an alphanumeric text field?    Field with value "00345ABC" would need to return "345ABC".
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That was an interview question that I was unable to answer:  How to check that a string is a palindrome using regular expressions?  p.s. There is already a question "" and it gives a lot of answers in different languages, but no answer that uses regular expressions.
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I'm developing an algorithm to parse a number out of a series of short-ish strings. These strings are somewhat regular, but there's a few different general forms and several exceptions. I'm trying to build a set of regexes that will handle the various forms and exceptions; I'll apply them one after another to see if I get a match.   One of these forms goes something like this:  X (Y) Z   Where:   X is a number I want to capture.  Z is static, pre-defined text. it's basically how I determine whether this particular form is applicable or not. Y is a a string of unknown length and content, surrounded by parenthesis.    Also: Y is optional; it doesn't always appear in a string with Z and X. So, I want to be able to extract the numbers from all of these strings:   10 Z 20 (foo) Z 30 (bar) Z   Right now, I have a regex that will capture the first one:  ([0-9]+) +Z   My problem is that I don't know how to construct a regex that will match a series of characters if and only if they're enclosed in parenthesis. Can this be done in a single regex?