13 Regular Expression with Grep Command RHCSA - Tech Arkit

1. Check Grep version

grep -V



2. Search single word in single file / multifles

grep string *



3. Search Multiple words in single file / multiple files

grep -E 'word1|word2'



4. Seach text which is not maching to string

grep -v "String" fileName



5. Print the matching string and its before lines

grep ens33 -A 4



6. Print the matching string and its after lines and its around lines

grep enss33 -B 4

grep ens33 -C 4



7. Search a string Recursively

grep -r string fileName



8. Grep the string with highlighted in color

grep --color=auto string file Name

export GREP_COLOR='1;30;43'



9. display the lines which does not matches all the given strings

grep -v -e "a" -e "b" -e "c" filename.txt



10. Get the count of given string from file

grep -c string filename



11. Search for files which are matching to the given string

grep -l this demo*



12. Beginning of line ^ using cap symble

grep "^Nov 10" messages.1



13. End of the line  $ using dollar symble

grep "terminating.$" messages



? The preceding item is optional and matched at most once.

* The preceding item will be matched zero or more times.

+ The preceding item will be matched one or more times.

n The preceding item is matched exactly n times.

n, The preceding item is matched n or more times.

,m The preceding item is matched at most m times.

n,m The preceding item is matched at least n times, but not more than m times.



From the above output you can come to know when all the messages has got interrupt. Just like ^ matches the beginning of the line only if it is the first character, $ matches the end of the line only if it is the last character in a regular expression.







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