16. Self-Learning Linux path: Text Processing tool Egrep,fgrep

Egrep: Use an extended regular expression to build the pattern, which is equivalent to GREP-E

　　Meta characters :

　　　　　　Character Matching :

. : Any single character

　　　　　　　　　[]: Specify any single character in the range

　　　　　　　　[^]: Any single character outside the specified range

　　　　　　number of matches :

　　　　　　　　　 *: Matches its preceding character any time

　　　　　　　　　?: Match its preceding character 0 or 1 times

+: Match its preceding character 1 or more times

　　　　　　　　　{m}: Matches M-Times

　　　　　　　　　{m,n}: At least m times, up to N times

　　　　　　　　　{m,}: at least m times

　　　　　　　　　{0,n}: Up to N times

　　　　　　 anchoring :

　　　　　　　　　^: Beginning of the line

　　　　　　　　　$: End of line

　　　　　　　　　\<,\b: the first word

　　　　　　　　　\>,\b: Ending

　　　　　　Group :

　　　　　　　　(): Group

　　　　　　　　　|: or example: AC|BC, which represents AC or BC, if a (c|b) C, indicates ACC,ABC

Fgrep:fast, do not parse regular expression, need to find what directly in the mode to fill in the corresponding content can be

Practice :

1. Find the line that ends with "LISTEN" or "established" in the results of the Netstat-tan command execution

　　#netstat-tan | grep--color=auto-e "listen| Established[[:space:]]* "

　　

2. Matching IP address

　#ifconfig | Grep-e--color=auto "(\< ([1-9]|[ 1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]) \>\.) {3} (\< ([0-9]|[ 1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]) \>) "

　　　　　　　　

16. Self-Learning Linux path: Text Processing tool Egrep,fgrep