How to negate specific word in regex

Question

I know that I can negate group of chars as in   bar  but I need a regular expression where negation applies to the specific word - so in my example how do I negate an actual bar  and not  any chars in bar

User · Answer

If it s truly a word  bar that you don t want to match  then          bbar b       The above will match any string that does not contain bar that is on a word boundary  that is to say  separated from non-word characters  However  the period dot     used in the above pattern will not match newline characters unless the correct regex flag is used      s       bbar b       Alternatively          bbar b   s S      Instead of using any special flag  we are looking for any character that is either white space or non-white space  That should cover every character   But what if we would like to match words that might contain bar  but just not the specific word bar       bbar b  b  A-Za-z-  bar a-z-   b        bbar b  Assert that the next input is not bar on a word boundary   b  A-Za-z-  bar a-z-   b Matches any word on a word boundary that contains bar    See Regex Demo

User · Answer

The accepted answer is  nice but is really a work-around for the lack of a simple sub-expression negation operator in regexes   This is why grep --invert-match exits   So in  nixes  you can accomplish the desired result using pipes and a second regex   grep  something I want    grep --invert-match  but not these ones    Still a workaround  but maybe easier to remember

User · Answer

The following regex will do what you want  as long as negative lookbehinds and lookaheads are supported   matching things properly  the only problem is that it matches individual characters  i e  each match is a single character rather than all characters between two consecutive  bar s   possibly resulting in a potential for high overhead if you re working with very long strings   b   ar     lt  b a a   r     lt  ba r   bar

User · Answer

Solution         STRING1   STRING2   STRING3       xxxxxx OK  xxxSTRING1xxx KO  is whether it is desired   xxxSTRING2xxx KO  is whether it is desired   xxxSTRING3xxx KO  is whether it is desired

User · Answer

A great way to do this is to use negative lookahead         bar          The negative lookahead construct is the pair of parentheses  with the opening parenthesis followed by a question mark and an exclamation point  Inside the lookahead  is any regex pattern

User · Answer

Unless performance is of utmost concern  it s often easier just to run your results through a second pass  skipping those that match the words you want to negate    Regular expressions usually mean you re doing scripting or some sort of low-performance task anyway  so find a solution that is easy to read  easy to understand and easy to maintain

User · Answer

I wish to complement the accepted answer and contribute to the discussion with my late answer    ChrisVanOpstal shared this regex tutorial which is a great resource for learning regex   However  it was really time consuming to read through   I made a cheatsheet for mnemonic convenience     This reference is based on the braces         and    leading each class  and I find it easy to recall   Regex       single character                 negate           capturing group                       backreferences and named group      repetition                                greedy v s  lazy      anchor                     b           non printable         n     t     r     f     v      shorthand             d     w     s

User · Answer

You could either use a negative look-ahead or look-behind          bar          lt  bar        Or use just basics         b   b       a  a       r         These all match anything that does not contain bar

User · Answer

Just thought of something else that could be done  It s very different from my first answer  as it doesn t use regular expressions  so I decided to make a second answer post   Use your language of choice s split   method equivalent on the string with the word to negate as the argument for what to split on  An example using Python    gt  gt  gt  text    barbarasdbarbar 1234egb ar bar32 sdfbaraadf   gt  gt  gt  text split  bar             asd         1234egb ar     32 sdf    aadf     The nice thing about doing it this way  in Python at least  I don t remember if the functionality would be the same in  say  Visual Basic or Java   is that it lets you know indirectly when  bar  was repeated in the string due to the fact that the empty strings between  bar s are included in the list of results  though the empty string at the beginning is due to there being a  bar  at the beginning of the string   If you don t want that  you can simply remove the empty strings from the list

User · Answer

I came across this forum thread while trying to identify a regex for the following English statement      Given an input string  match everything unless this input string is exactly  bar   for example I want to match  barrier  and  disbar  as well as  foo     Here s the regex I came up with     bar      bar        My English translation of the regex is  match the string if it starts with  bar  and it has at least one other character  or if the string does not start with  bar

User · Answer

I had a list of file names  and I wanted to exclude certain ones  with this sort of behavior  Ruby    files        mydir states rb          don t match these    countries rb      mydir states bkp rb      match these    mydir city states rb     excluded     states    countries      set my rgx here  result   WankyAPI filter files  my rgx     I didn t write WankyAPI    assert result      mydir city states rb    mydir states bkp rb     Here s my solution   excluded rgx   excluded map  e  e       join      my rgx                excluded rgx             rb     My assumptions for this application    The string to be excluded is at the beginning of the input  or immediately following a slash  The permitted strings end with  rb  Permitted filenames don t have a   character before the  rb

User · Answer

Extracted from this comment by bkDJ       bar       The nice property of this solution is that it s possible to clearly negate  exclude  multiple words       bar  foo  banana

[regex] How to negate specific word in regex?

Examples related to regex