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- grep a matches.txt # find lines containing 'a'
- grep ab matches.txt # find lines containing 'abc'
- grep '^ab$' matches.txt # find lines starting with 'abc'
- grep "[hat]" matches.txt # find lines containing h, a or t
- grep -E "[abc]{3,4}" matches.txt # find strings with 3 or 4 successive combination of a, b or c
- grep -E -n -o "[abc]{3,4}" matches.txt # show line numbers and matches only
- ip addr | egrep "([0-9]{1,3}\.){3}[0-9]{1,3}" # find IP addresses
- ip addr | egrep "([[:xdigit:]]{2}:){5}[[:xdigit:]]{2}" # find MAC Addresses
- grep "[[:punct:]]" matches.txt # find punctuation
- grep "[linux]{3,5}" regex.examples # find l,i,n,u, or x in a pattern between 3 to 5 characters
- egrep "[linux]{3,5}" regex.examples # did it work now?
- grep '[[:alpha:]]' regex.examples # find lettes
- fgrep '[[:alpha:]]' regex.examples # find the single quote enclosed string explicitly
- grep "[[:blank:]]" matches.txt # find space or tab
- grep "[[:space:]]" matches.txt # find all whitespace
- grep "[[:blank:]]$" matches.txt # find space or tab at the line’s end
- grep "[[:space:]]$" matches.txt # find whitespace at the line’s end
- grep -i uuid /etc/fstab # find the 'uuid' string
- sed -e 's/UUID/uuid' /etc/fstab | grep uuid # case sensitive
- sed 's/UUID/UUID UUID/' /etc/fstab | sed 's/UUID/uuid/' # replace only the first match of UUID
- sed 's/UUID/UUID UUID/' /etc/fstab | sed 's/UUID/uuid/g' # replace all matches of UUID
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