大家好，又见面了，我是你们的朋友全栈君。
linux是一个相对安全的系统， 其中的权限更是无处不在。 在本文中， 我们来谈谈linux中的文件/目录的rwx权限。 为了简便起见， 我们仅仅以文件owner的rwx为例。
一. 文件的rwx权限分别是什么意思？
1. r权限：可读权限， 验证如下：
total 0
[taoge@localhost learn_c]$ echo hello > a.txt
[taoge@localhost learn_c]$ ls -l
total 4
-rw-rw-r– 1 taoge taoge 6 May 6 03:51 a.txt
[taoge@localhost learn_c]$ chmod 000 a.txt
[taoge@localhost learn_c]$ ls -l
total 4
———- 1 taoge taoge 6 May 6 03:51 a.txt
[taoge@localhost learn_c]$ cat a.txt
cat: a.txt: Permission denied
[taoge@localhost learn_c]$ chmod u+r a.txt
[taoge@localhost learn_c]$ ls -l
total 4
-r——– 1 taoge taoge 6 May 6 03:51 a.txt
[taoge@localhost learn_c]$ cat a.txt
hello
[taoge@localhost learn_c]$
2. w权限： 可写权限， 验证如下：
total 0
[taoge@localhost learn_c]$ touch a.txt
[taoge@localhost learn_c]$ ls -l
total 0
-rw-rw-r– 1 taoge taoge 0 May 6 03:56 a.txt
[taoge@localhost learn_c]$ chmod 000 a.txt
[taoge@localhost learn_c]$ ls -l
total 0
———- 1 taoge taoge 0 May 6 03:56 a.txt
[taoge@localhost learn_c]$ chmod u+w a.txt
[taoge@localhost learn_c]$ ls -l
total 0
–w——- 1 taoge taoge 0 May 6 03:56 a.txt
[taoge@localhost learn_c]$ echo hello > a.txt
[taoge@localhost learn_c]$ cat a.txt
cat: a.txt: Permission denied
[taoge@localhost learn_c]$ chmod u+r a.txt
[taoge@localhost learn_c]$ cat a.txt
hello
[taoge@localhost learn_c]$
3. x权限：可执行权限， 验证如下：
total 4
-rw-rw-r– 1 taoge taoge 65 May 6 04:02 test.c
[taoge@localhost learn_c]$ cat test.c
#include <stdio.h>
int main()
{
printf(“good\n”);
return 0;
}
[taoge@localhost learn_c]$ gcc test.c
[taoge@localhost learn_c]$ ls -l
total 12
-rwxrwxr-x 1 taoge taoge 4638 May 6 04:04 a.out
-rw-rw-r– 1 taoge taoge 65 May 6 04:02 test.c
[taoge@localhost learn_c]$ ./a.out
good
[taoge@localhost learn_c]$ chmod 000 a.out
[taoge@localhost learn_c]$ ./a.out
bash: ./a.out: Permission denied
[taoge@localhost learn_c]$ chmod u+x a.out
[taoge@localhost learn_c]$ ./a.out
good
[taoge@localhost learn_c]$
二. 目录的rwx权限分别是什么意思？
1. r权限：可读权限（可列举查看目录下的内容）， 验证如下：
total 0
[taoge@localhost learn_c]$ ls -l
total 4
drwxrwxr-x 2 taoge taoge 4096 May 6 04:07 test
[taoge@localhost learn_c]$ touch ./test/a.txt
[taoge@localhost learn_c]$ ls ./test/
a.txt
[taoge@localhost learn_c]$ chmod u-r test/
[taoge@localhost learn_c]$ ls ./test/
ls: cannot open directory ./test/: Permission denied
[taoge@localhost learn_c]$
2. w权限：可写权限（可以往目录中写东东， 比如文件）， 验证如下：
total 0
[taoge@localhost learn_c]$ mkdir test
[taoge@localhost learn_c]$ ls -l
total 4
drwxrwxr-x 2 taoge taoge 4096 May 6 04:13 test
[taoge@localhost learn_c]$ touch ./test/a.txt
[taoge@localhost learn_c]$ chmod u-w test
[taoge@localhost learn_c]$ touch ./test/b.txt
touch: cannot touch `./test/b.txt’: Permission denied
[taoge@localhost learn_c]$
3. x权限: 可执行权限（可以cd进去）， 验证如下：
total 0
[taoge@localhost learn_c]$ mkdir test
[taoge@localhost learn_c]$ ls -l
total 4
drwxrwxr-x 2 taoge taoge 4096 May 6 04:17 test
[taoge@localhost learn_c]$ cd test/
[taoge@localhost test]$ cd –
/home/taoge/Desktop/learn_c
[taoge@localhost learn_c]$ chmod u-x test/
[taoge@localhost learn_c]$ cd test/
bash: cd: test/: Permission denied
[taoge@localhost learn_c]$
好，最后我们再来看一个问题：在某目录test中创建一个文件或者删除一个文件， 需要test目录具备什么权限呢？ 答曰：需要目录test具备wx权限, 验证如下：
total 0
[taoge@localhost learn_c]$ mkdir test
[taoge@localhost learn_c]$ touch ./test/a.txt ./test/b.txt ./test/c.txt ./test/d.txt
[taoge@localhost learn_c]$ ls -l
total 4
drwxrwxr-x 2 taoge taoge 4096 May 6 04:33 test
[taoge@localhost learn_c]$ chmod u-r test/
[taoge@localhost learn_c]$ touch ./test/e.txt
[taoge@localhost learn_c]$ chmod u-w test/
[taoge@localhost learn_c]$ touch ./test/f.txt
touch: cannot touch `./test/f.txt’: Permission denied
[taoge@localhost learn_c]$ rm ./test/a.txt
rm: cannot remove `./test/a.txt’: Permission denied
[taoge@localhost learn_c]$ chmod u+w test/
[taoge@localhost learn_c]$ chmod u-x test/
[taoge@localhost learn_c]$ touch ./test/f.txt
touch: cannot touch `./test/f.txt’: Permission denied
[taoge@localhost learn_c]$ rm ./test/a.txt
rm: cannot remove `./test/a.txt’: Permission denied
[taoge@localhost learn_c]$ chmod u+x test/
[taoge@localhost learn_c]$
因此， 如果某一目录test删除不掉， 很可能是因为其中有不可删除的文件， 从本质上来讲， 就是test自己没有wx权限了。
好， 本文先闲谈到这里。
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