【Linux题目】第五关

方法1:用sed获取stat filename里的属性值
[root@oldboy oldboy]# stat oldboy.txt|sed -nr ‘4s#.*([0-9]{4}).*#\1#gp‘ 
0644

方法2: 获取到权限值，用tr替换rwx-
注意，替换的顺序，-rwx，会把-r认为是参数，出错。
[root@oldboy oldboy]# ls -l oldboy.txt|cut -c2-10|tr "-rwx" "0421"
tr: invalid option -- ‘r‘
Try `tr --help‘ for more information.
[root@oldboy oldboy]# ls -l oldboy.txt|cut -c2-10|tr "rwx-" "4210"
420400400
[root@oldboy oldboy]# ls -l oldboy.txt|cut -c2-10|tr "rwx-" "4210"|awk -F "" ‘{print $1+$2+$3,$4+$5+$6,$7+$8+$9}‘ 
6 4 4

方法3:
[root@oldboy oldboy]# stat oldboy.txt|awk -F "[(/)]" ‘NR==4 {print $2}‘  
0644

方法4: 用stat filename的自带参数
[root@oldboy oldboy]# stat oldboy.txt -c %a
644

-c --format=FORMAT
        use  the  specified FORMAT instead of the default; output a newline after each use of
        FORMAT
The valid format sequences for files (without --file-system):
   %a     Access rights in octal

   %A     Access rights in human readable form

   %b     Number of blocks allocated (see %B)

   %B     The size in bytes of each block reported by %b

   %C     SELinux security context string
...

[root@oldboy /]# mkdir /oldboy/ett -p
[root@oldboy /]# ls -ld /oldboy/ett
drwxr-xr-x 2 root root 4096 Sep  5 22:17 /oldboy/ett
# 包含本身和‘.‘ 互为硬链接目录

[root@oldboy /]# mkdir /oldboy/ett/test
[root@oldboy /]# ls -ld /oldboy/ett
drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett
# 包含本身和‘.‘ 互为硬链接，还有一个‘..‘
[root@oldboy /]# ls -alid /oldboy/ett/ /oldboy/ett/.      
275739 drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett/
275739 drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett/.

[root@oldboy /]# ls -ld /oldboy/ett/test
drwxr-xr-x 2 root root 4096 Sep  5 22:17 /oldboy/ett/test
[root@oldboy /]# ls -alid /oldboy/ett/test/. /oldboy/ett/test
275740 drwxr-xr-x 2 root root 4096 Sep  5 22:17 /oldboy/ett/test
275740 drwxr-xr-x 2 root root 4096 Sep  5 22:17 /oldboy/ett/test/.

[root@oldboy /]# ls -alid /oldboy/ett/ /oldboy/ett/. /oldboy/ett/test/..
275739 drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett/
275739 drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett/.
275739 drwxr-xr-x 3 root root 4096 Sep  5 22:17 /oldboy/ett/test/..

[root@oldboy /]# ifconfig eth3|sed -nr ‘2s#^.*dr:([0-9.]+)  B.*$#\1#gp‘  
192.168.0.109

[root@oldboy /]# ifconfig eth3|grep ‘inet‘|awk -F "[: ]+" ‘{print $4}‘
192.168.0.109

[root@oldboy /]# ifconfig eth3|grep ‘inet‘|cut -d ":" -f 2|cut -d " " -f1
192.168.0.109

[root@oldboy /]# ifconfig eth3|awk -F "[: ]+" ‘NR==2{print $4}‘            
192.168.0.109

[root@oldboy test]# cat /etc/resolv.conf 
; generated by /sbin/dhclient-script
nameserver 192.168.1.1
nameserver 192.168.0.1

[root@oldboy /]# echo ‘oldboy‘;echo ‘oldboy‘
oldboy
oldboy
[root@oldboy /]# echo ‘oldboy‘ -n ;echo ‘oldboy‘ 
oldboy -n
oldboy
[root@oldboy /]# echo -n ‘oldboy‘;echo ‘oldboy‘   # -n参数 
oldboyoldboy