Regex – Grep regex NOT containing string


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 "1\.2\.3\.4.*Has exploded" syslog.log

It's just a list of patterns like the "1\.2\.3\.4.*Has exploded" part I am passing, in a loop, so I can't pass "-v" 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 "!*Has exploded" will match syslog lines for anything other than 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?

This is happening in a script like this;

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}
 grep "${patterns[$i]}" logfile.log

Best Solution

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}"