Grep regex NOT containing string

Question

I am passing a list of regex patterns to grep to check against a syslog file  They are usually matching an IP address and log entry  grep  quot 1  2  3  4  Has exploded quot  syslog log  It s just a list of patterns like the  quot 1  2  3  4  Has exploded quot  part I am passing  in a loop  so I can t pass  quot -v quot  for example  I am confused trying to do the inverse of the above  and NOT match lines with a certain IP address and error so  quot  1 2 3 4  Has exploded quot  will match syslog lines for anything other than 1 2 3 4 telling me it has exploded  I must be able to include an IP to NOT match  I have seen various similar posts on StackOverflow  However they use regex patterns that I can t seem to get to work with grep  Can anyone provide a working example for grep please  UPDATE  This is happening in a script like this  patterns 1   quot 1  2  3  4  Has exploded quot  patterns 2   quot 5  6  7  8  Has died quot  patterns 3   quot   9  10  11  12  Has exploded quot   for i in  1  3  do  grep  quot   patterns  i   quot  logfile log done

User · Accepted Answer

grep matches  grep -v does the inverse  If you need to  match A but not B  you usually use pipes   grep    PATT   file   grep -v    NOTPATT

User · Answer

lt  1  2  3  4   Has exploded   You need to run this with -P to have negative lookbehind  Perl regular expression   so the command is   grep -P     lt  1  2  3  4   Has exploded  test log   Try this   It uses negative lookbehind to ignore the line if it is preceeded by 1 2 3 4   Hope that helps

User · Answer

patterns 1   1  2  3  4  Has exploded  patterns 2   5  6  7  8  Has died  patterns 3     9  10  11  12  Has exploded   for i in  1  3   do grep    patterns  i    logfile log done   should be the the same as   egrep   1  2  3  4  Has exploded 5  6  7  8  Has died   logfile log   egrep -v  9  10  11  12  Has exploded

[regex] Grep regex NOT containing string

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