Linux chmod usage

Command name: chmod permission: usage of all users: chmod [-CFVR] [-- help] [-- version] mode file... note: The file calling permissions for Linux/Unix are divided into three levels: file owner, group, and others. Chmod can be used to control how files are called by others. Parameter: Mode: permission setting string. Format: [ugoa...] [[+-=] [rwxx]...] [,...], U indicates the owner of the file, G indicates that the owner of the file belongs to the same group, O indicates that the owner of the file belongs to other people, and 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 of the file has been changed, the change action is displayed.-F: if the permission of the file cannot be changed, do not display the error message-V: show Details of permission change-R: perform the same permission change on all files in the current directory and sub-directories (that is, change one by one in the way of delivery) -- help: show auxiliary instructions -- version: Show version example: Set the file file1.txt to everyone to read: chmod Ugo + R file1.txt set the file file1.txt to everyone to read: chmod A + R file1.txt sets the archive file1.txt and file2.txt as the owner of the archive, which can be written to the same group to which the archive belongs, but cannot be written to other people: chmod ug + W, o-w file1.txt file2.txt set ex1.py to run: chmod U + x ex1.py to run all files and sub-files in the current directory The directory is set to readable by anyone: chmod-r a + R *. In addition, chmod can also use numbers to indicate permissions. For example, chmod 777 File Syntax is: chmod ABC file where A, B, 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. Example: chmod A = rwx file and chmod 777 file have the same effect as chmod ug = rwx, O = X file and chmod 771 file have the same effect. If chmod 4755 filename is used, this program has the root permission.

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