Shell中正则表达式及sed和awk常见问题

准备测试文件：
[root@svr5 ~]# cat tel.txt 
01012315
137012345678
13401234567
10086
18966677788
提取包含11位手机号的行：
[root@svr5 ~]# egrep '^1[0-9]{10}$' tel.txt 
13401234567
18966677788

[root@svr5 ~]# cat -n /etc/rc.local 
     1  #!/bin/sh
     2  #
     3  # This script will be executed *after* all the other init scripts.
     4  # You can put your own initialization stuff in here if you don't
     5  # want to do the full Sys V style init stuff.
     6
     7  touch /var/lock/subsys/local

[root@svr5 ~]# cat -n /etc/rc.local | sed -n '2~2p'
     2  #
     4  # You can put your own initialization stuff in here if you don't
     6

[root@svr5 ~]# cat /etc/rc.local 
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local

[root@svr5 ~]# cat /etc/rc.local | sed 's/.//4'
#!/in/sh
#
# Tis script will be executed *after* all the other init scripts.
# Yu can put your own initialization stuff in here if you don't
# wnt to do the full Sys V style init stuff.
touh /var/lock/subsys/local

[root@svr5 ~]# sed -n '6,10p' /etc/passwd > pass5.txt

[root@svr5 ~]# cat pass5.txt 
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin

[root@svr5 ~]# ip add list eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:64:88:8e brd ff:ff:ff:ff:ff:ff
    inet 192.168.4.55/24 brd 192.168.4.255 scope global eth0
    inet 192.168.4.5/24 brd 192.168.4.255 scope global secondary eth0
    inet6 fe80::20c:29ff:fe64:888e/64 scope link 
       valid_lft forever preferred_lft forever

[root@svr5 ~]# ip add list eth0 | awk '/\<inet\>/{print $2}'
192.168.4.55/24
192.168.4.5/24

[root@svr5 ~]# awk -F: '$3>=10 && $3<=20{print $1":"$3}' /etc/passwd
uucp:10
operator:11
games:12
Gopher:13
ftp:14

[root@svr5 ~]# awk -F/ '$NF=="bash"{x++}END{print x}' /etc/passwd

[root@svr5 ~]# sort –n abc.txt