[root@linuxstudy testshell]# cut -d: -f 1 /etc/passwd
root
bin
daemon
adm
lp
sync
shutdown
halt
mail
uucp
operator
games
gopher
ftp
nobody
dbus
usbmuxd
vcsa
rtkit
avahi-autoipd
abrt
haldaemon
gdm
ntp
apache
saslauth
postfix
pulse
sshd
tcpdump
wujihu
hadoop
mysql
[root@linuxstudy testshell]# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
[root@linuxstudy sh]# sed -i '/andy/d' stest.txt
[root@linuxstudy sh]# cat stest.txt
id name gender mark
1 jack m 90
3 jimmy m 88
4 miki f 86
[root@linuxstudy sh]# wc -l stest.txt
4 stest.txt
[root@linuxstudy sh]# wc -l student.txt
5 student.txt
[root@linuxstudy sh]# wc -l student.txt
5 student.txt
[root@linuxstudy sh]# cat stest.txt
id name gender mark
1 jack m 90
3 jimmy m 88
4 miki f 86
[root@linuxstudy sh]# sed -i '4d' stest.txt
[root@linuxstudy sh]# cat stest.txt
id name gender mark
1 jack m 90
3 jimmy m 88
[root@linuxstudy sh]# sed -i '1d' stest.txt
[root@linuxstudy sh]# cat stest.txt
1 jack m 90
3 jimmy m 88
[root@linuxstudy sh]#