Shell脚本(篇五)

1.简述sed定址符的作用及表示方式。

作用：控制sed处理文本的范围；不加定址符则逐行处理所有行
表示方式：行号或正则表达式

2.如何使用sed提取文本中的偶数行？

查看测试文本：
[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

提取偶数行的操作及效果：
[root@svr5 ~]# cat -n /etc/rc.local | sed -n 'n;p'
     2  #
     4  # You can put your own initialization stuff in here if you don't
     6

3.如何使用sed删除文本中每行的第4个字符？

查看测试文本：
[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

删除每行第4个字符的操作及效果：

[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

4.在指定文本的第二行插入两行chkconfig配置信息。

新建系统服务脚本时，需要添加支持chkconfig管理的配置信息，文本内容如下：
# chkconfig: - 85 24 
# description: Startup script for httpd server. (for Test only)

建立测试文件：
[root@svr5 ~]# vim chksrv
!/bin/bash
case "$1" in
start)
.. ..
在chksrv文件的第二行之后添加新的内容：
[root@svr5 ~]# sed -i '2i# chkconfig: - 85 24\
# description: Startup script for httpd server. (for Test only)' chksrv 
!/bin/bash
# chkconfig: - 85 24
# description: Startup script for httpd server. (for Test only)
case "$1" in
start)
.. ..
确认修改结果：
[root@svr5 ~]# cat chksrv 
!/bin/bash
# chkconfig: - 85 24
# description: Startup script for httpd server. (for Test only)
case "$1" in
start)
.. ..

5.提取/etc/passwd文件的第6-10行，另存为pass5.txt文件。

提取或导出文本：
[root@svr5 ~]# sed -n '6,10p' /etc/passwd > pass5.txt
或者：
[root@svr5 ~]# sed -n '6,10w pass5.txt' /etc/passwd
确认提取结果：
[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

6.如何使用sed将文本的第3-4行移动到原来的第6行之后？

查看测试文本：
[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
剪切操作及效果：
[root@svr5 ~]# cat -n /etc/rc.local | sed '3h;4H;3,4d;6G'
     1  #!/bin/sh
     2  #
     5  # want to do the full Sys V style init stuff.
     6
     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
     7  touch /var/lock/subsys/local

上述操作中，sed编辑指令分别解析如下：
3h：取第3行内容，覆盖到保持空间
4H：取第4行内容，追加到保持空间
3,4d：删除第3-4行内容
6G：找到第6行，将保持空间的内容追加到这