How to inverse match with regex

Question

I m using RegexBuddy but I m in trouble anyway with this thing     I m processing line by line a file  I built a  line model  to match what I want   Now i d like to do an inverse match    i e  I want to match lines where there is a string of 6 letters  but only if these six letters are not Andrea  how should I do that     EDIT  I ll write the program that uses this regex  I don t know yet if in python or php  I m doing this thing first to learn some regex    There are different types of line  I wanted to use regex to select the type i m interested in  Once I got these lines I ve to apply an other filter just to do not match a known value  I need all the others  not that  The    not-wanted  is working pretty fine  thank you   -   I hope this clarifies the question

User · Answer

Updated with feedback from Alan Moore  In PCRE and similar variants  you can actually create a regex that matches any line not containing a value          Andrea        This is called a tempered greedy token   The downside is that it doesn t perform well

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In perl you can do   process  line  if   line      Andrea

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For Python Java           some text        http   www lisnichenko com articles javapython-inverse-regex html

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Negative lookahead assertion     Andrea    This is not exactly an inverted match  but it s the best you can directly do with regex  Not all platforms support them though

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If you want to do this in RegexBuddy  there are two ways to get a list of all lines not matching a regex   On the toolbar on the Test panel  set the test scope to  Line by line    When you do that  an item List All Lines without Matches will appear under the List All button on the same toolbar    If you don t see the List All button  click the Match button in the main toolbar    On the GREP panel  you can turn on the  line-based  and the  invert results  checkboxes to get a list of non-matching lines in the files you re grepping through

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is useful in practice  Although strictly speaking  looking ahead is not regular expression as defined mathematically   You can write an invert regular expression manually   Here is a program to calculate the result automatically  Its result is machine generated  which is usually much more complex than hand writing one  But the result works

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I just came up with this method which may be hardware intensive but it is working   You can replace all characters which match the regex by an empty string    This is a oneliner   notMatched   re sub regex      string   I used this because I was forced to use a very complex regex and couldn t figure out how to invert every part of it within a reasonable amount of time    This will only return you the string result  not any match objects

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What language are you using   The capabilities and syntax of the regex implementation matter for this   You could use look-ahead   Using python as an example  import re  not andrea   re compile     Andrea  w 6    re IGNORECASE    To break that down      Andrea  means  match if the next 6 characters are not  Andrea    if so then   w means a  word character  - alphanumeric characters   This is equivalent to the class  a-zA-Z0-9     w 6  means exactly 6 word characters   re IGNORECASE means that you will exclude  Andrea    andrea    ANDREA       Another way is to use your program logic - use all lines not matching Andrea and put them through a second regex to check for 6 characters   Or first check for at least 6 word characters  and then check that it does not match Andrea

User · Answer

If you want to do this in RegexBuddy  there are two ways to get a list of all lines not matching a regex   On the toolbar on the Test panel  set the test scope to  Line by line    When you do that  an item List All Lines without Matches will appear under the List All button on the same toolbar    If you don t see the List All button  click the Match button in the main toolbar    On the GREP panel  you can turn on the  line-based  and the  invert results  checkboxes to get a list of non-matching lines in the files you re grepping through

User · Answer

Andrea   6    Assuming your regexp engine supports negative lookaheads    Edit    or maybe you d prefer to use  A-Za-z  6  in place of   6   Edit  again   Note that lookaheads and lookbehinds are generally not the right way to  inverse  a regular expression match  Regexps aren t really set up for doing negative matching  they leave that to whatever language you are using them with

[regex] How to "inverse match" with regex?

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