Linux 中几个正则表达式的用法

ifconfig | head -n 2 |tail -1 |tr -s " " |cut -d" " -f3

df |tr -s " " |cut -d" " -f5

cat /etc/passwd | cut -d: -f1,3,7| sort -nt: -k2 |tail -n 1

stat /tmp | head -n 4 |tail -n 1|cut -c10-13

cat /etc/passwd |cut -d: -f1,3 | egrep -v "[0-9]{4,}"

cat /etc/passwd |egrep "^(root|A8)" |cut -d: -f1,3

echo /etc/rc.d/init.d/functions | egrep "[a-z]$"

echo /etc/rc.d/init.d/functions | egrep "/.*/"

echo {1..255} | egrep "\<[0-9]\>"

egrep "\<1[0-9]\>"

egrep "\<1[0-9][0-9]\>"

egrep "\<2[0-4][0-9]\>"

egrep "\<25[0-5]\>"

ifconfig |egrep "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}"