Function: In the Linux command, chmod to modify a file or directory permissions.
Role: You can make a person designated by modifying the permissions to the file readable, writable, run, greatly ensure the security of the data.
Rookie explain: file permissions calling Linux / Unix is divided into three levels: file owner, group, others. Chmod can use so as to control how the file is called by others.
Usage rights : All users
grammar
chmod [-cfvR] [--help] [--version] mode file...
Parameter Description
mode: permissions string in the following format:
[ugoa...][[+-=][rwxX]...][,...]
among them:
- u represents the owner of the file, g represents the owner of the file belonging to the same group (group) who, o represents other than human, a represents three both.
- + Indicates increased authority - indicates remove permissions, = represents a unique set permissions.
- r represents read, w represents the writing, x represents an executable , X is only when this file is a subdirectory or file has been set through the executable.
Other parameters:
- -c: If the file permissions have changed indeed, it shows the change action
- -f: If the file permissions can not be changed and do not display an error message
- Details show permission to change: -v
- -R: all the files and subdirectories in the current directory the same change permissions (that is handed back to the way one by one to change)
- --help: display HELP
- --version: show the version
Detailed structure chmod command:
Enter in Linux ll, detailed information file / directory specified directory appears article focuses on rights section, part of the figure is under the red box.
Detailed the FIG: Permissions total of 10 characters, the first character is divided into a group, and a nine characters divided into three groups.
The first character in two cases: if it is "d" represents this is a folder, if it is "-" It is on behalf of a file;
2,3,4 characters : these three characters together on behalf of the owner of the file, u can be represented, with four privileges: r: read permission, w: write permission, x: execute permission, -: No permission;
5,6,7 characters : three characters represents the file belongs to a group, can be expressed by g, has four rights: r: read permission, w: write permission, x: execute permission, -: No authority;
9, 10 characters : all other users on behalf of these three characters other than the owner and owning group, o can be represented, with four privileges: r: read permission, w: write permissions, x: execute permission, -: no authority.
Note: In addition to the back of 9 characters u, g, o, and a a, on behalf of all users.
Practical operation of verification:
1. start_nodejs.sh stop_nodejs.sh modify the executable permissions
[154.8.159.209:root@xlp117 / var / www / html / Qiantai / nodejs / smsAdapter] # chmod + x start_nodejs.sh stop_nodejs.sh
before fixing:
Modified:
2. start_nodejs.sh stop_nodejs.sh executable permissions before modify and cancel [as] not screenshots
[154.8.159.209:root@xlp117 / var / www / html / Qiantai / nodejs / smsAdapter] # chmod -x start_nodejs.sh stop_nodejs.sh
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Reference link: https: //blog.csdn.net/jerrytomcat/article/details/81744860