Linux_ file Permissions

this blog post for the original, reproduced please specify the source! http://blog.csdn.net/zimo2013/article/details/39339973

The Linux system uses 10-bit (b it) data to represent access rights, such as access to a file as follows.

-rw-r--r--@1 Keyd Staff 9 23:32 makefile.mk! Drwxr-xr-x 4 Keyd Staff 136

Bit0: Use -or D indicates that the former indicates this is a file, which indicates that this is a directory.
BITL-BIT3: user's own access to the file.
BIT4?BIT6: user groups (group) access to the file.

Bit7?bit9: Other User (other ) access to the file.

$chmod u+x copy.sh

The meaning of u+x in the command is to add execute (x) permissions to the user, similar to o+x, O+RW, g+rwx, and so on. For ease of use, a is used to represent three types of users, such as A+x, a+rwx, and so on, where a stands for all, that is, all three types of users.
for some Linux systems, such as the Linux,chmod command at the bottom of the Android phone does not recognize parameters such as R, W, X, and can only be represented by a 8 binary numeric value, such as:

$chmod 777 copy.sh

the number of the 777 is 8, the corresponding binary data is 111 111 111, which represents the U, G, O Three types of user access rights.

Linux_ file Permissions