linux基础学习-12.3-对于文件来说r w x 是什么含义？

1、创建环境

mkdir -p /oldboy

echo 'hostname' > /oldboy/oldwang.sh

chown oldboy.oldboy /oldboy/oldwang.sh

2、文件的R权限

###root 用户下面 修改权限 文件的r

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

-rw-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh

[root@oldboyedu42-lnb oldboy]# chmod u=r oldwang.sh

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

-r--r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh

###oldboy用户测试

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

hostname

[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh

-bash: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh

-bash: /oldboy/oldwang.sh: Permission denied

3、文件的W权限

###root 用户下面 修改权限 文件的w

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

-r--r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh

[root@oldboyedu42-lnb oldboy]# chmod u=w oldwang.sh

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

--w-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh

###oldboy 用户

[oldboy@oldboyedu42-lnb oldboy]$ ll /oldboy/oldwang.sh

--w-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 /oldboy/oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ cat /oldboy/oldwang.sh

cat: /oldboy/oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh

-bash: /oldboy/oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh

~

~

~

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh

w-r--r-- 1 oldboy oldboy 21 Nov 3 18:23 oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh

alias rm

~

~

~

"oldwang.sh" 1L, 9C written

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

cat: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

cat: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

cat: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

cat: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh

--wxr--r-- 1 oldboy oldboy 9 Nov 3 18:25 oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh

~

~

~

~

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

ias rm

[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh

alias rm

pwd

~

~

~

~

"oldwang.sh" 2L, 13C written

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

alias rm

pwd

小结：

对于文件的w权限

1.修改文件的内容，w权限需要有人r权限配合

2.如果没有r权限，使用vi/vim 修改文件内容 会导致源文件内容清空

3、文件的X权限

###root 用户下面 修改权限 文件的x

[root@oldboyedu42-lnb oldboy]# chmod u=x oldwang.sh

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

---xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh

###oldboy

[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh

---xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh

cat: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh

-bash: oldwang.sh: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh

bash: /oldboy/oldwang.sh: Permission denied

4、文件的rx权限

###root 用户下面 修改权限 文件的rx

[root@oldboyedu42-lnb oldboy]# ll oldwang.sh

-r-xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh

###oldboy

[oldboy@oldboyedu42-lnb oldboy]$ cat /oldboy/oldwang.sh

pwd

[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh

/oldboy

[oldboy@oldboyedu42-lnb oldboy]$ ll /oldboy/oldwang.sh

-r-xr--r-- 1 oldboy oldboy 4 Nov 3 18:34 /oldboy/oldwang.sh

[oldboy@oldboyedu42-lnb oldboy]$

下面为何报错的原因是什么？

[oldboy@oldboyedu42-lnb oldboy]$ echo '#' >> /etc/hosts

-bash: /etc/hosts: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ echo '#' >> /etc/hosts

-bash: /etc/hosts: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ ls -l /etc/hosts

-rw-r--r--. 2 root root 194 Nov 11 2017 /etc/hosts

[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户

[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户与这个文件关系: 陌生人

[oldboy@oldboyedu42-lnb oldboy]$ id oldboy

uid=500(oldboy) gid=500(oldboy) groups=500(oldboy)

[oldboy@oldboyedu42-lnb oldboy]$

[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户对这个文件权限 最后三位 r--

[oldboy@oldboyedu42-lnb oldboy]$ cat /etc/shadow

cat: /etc/shadow: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ cat /etc/sudoers

cat: /etc/sudoers: Permission denied

[oldboy@oldboyedu42-lnb oldboy]$ ll /etc/sudoers

-r--r-----. 1 root root 3729 Dec 8 2015 /etc/sudoers

#1.oldboy

#2.oldboy 陌生人

#3.最后三位 ---

5、文件的读写执行小结(限制普通用户)：

1.r查看文件的内容

2.w修改文件的内容，需要r的配合

如果没有r权限，使用vi/vim 修改文件内容 会导致源文件内容清空

3.x执行文件（命令或脚本），需要r的配合

练习题：

详细说出rwx在文件中的意义