Chmod is one of the common commands in linux. It is mainly used to change the permissions of folders or files. It is often used in website deployment.
This command is executed by the root user or the user granted the relevant permissions.
Command Format: chmod [-cfvR] [-- help] [-- version] file or folder
Parameter description:
Permission setting string in the following format:
[Ugoa] [[+-=] [rwxX]...] [,...], u indicates the owner of the file or directory, g indicates that the owner of the file or directory belongs to the same group, and o indicates the owner of other files or directories, a indicates that all three are. + Adds a permission,-Indicates canceling the permission, and = indicates a unique permission. R indicates that the file can be read, w indicates that the file can be written, and x indicates that the file can be executed only when the file is a subdirectory or the file has been set to executable. -C: if the permission has been changed, the change action is displayed.-f: if the permission cannot be changed, no error message is displayed.-v: detailed information about permission change-R: change the permissions of all files and sub-directories in the current directory in the same way (that is, change one by one in the way of delivery) -- help: display auxiliary instructions -- version: display version
Example:
Set file1.txt to readable by all users:
chmod ugo+r file1.txt
Set file1.txt and file2.txt as the owner of the file, which can be written to the same group, but not to others:
chmod ug+w,o-w file1.txt file2.txt
Set ex1.py to be executed only by the file owner:
chmod u+x ex1.py
Set all files and subdirectories in the current directory to be readable by anyone:
chmod -R a+r *
In addition, chmod can use numbers to indicate permissions, such as chmod 777 file.
Syntax: chmod abc file
Each a, B, and c is a number, indicating the permissions of the User, Group, and Other respectively.
R = 4, w = 2, x = 1 if you want the rwx attribute, 4 + 2 + 1 = 7; if you want the rw-attribute, 4 + 2 = 6; if you want the r-x attribute, 4 + 1 = 7.
For example:
Chmod a = rwx file and chmod 777 file have the same effect
Chmod ug = rwx, o = x file, and chmod 771 file have the same effect.
