61-umask Concise Notes

Set the permission mask when creating a file

umask [Mask]

Parameters

Mask can be a 3-bit octal number or a symbol value as used in chmod ,mask Specifies the disallowed permission (the actual permission of the file is 777 minus the umask value)

If there are no parameters, then umask will display the permission mask when the file is created

Options

-S gives the permission mask when creating the file in the form of a symbol

Exampleumask

$ umask0022

Displays the permissions that are not allowed by default when creating a file, regardless of the 1th bit

Group users and other users are not allowed to have write permissions here

umask-s

$ umask-su=rwx,g=rx,o=rx

Show default Permissions

umask Setting Masks

$ umask u=rw,g=r,o=r$ umask0133$ umask-su=rw,g=r,o=r

Set a mask as a character

umask Setting Masks

$ umask 022$ umask0022$ Umask-su=rwx,g=rx,o=rx

Set a mask numerically

Tips

1. Regardless of the mask value, most programs do not attempt to create a file with Execute permissions (this is a unspoken rule) because they do not consider it necessary to create an executable file

Therefore, when a utility (such as touch) creates a file, the system uses 6 minus each number in mask

2.mkdir is a special case, it assumes that the user does need to set executable permissions, so that the directory can be executed (into the directory)

61-umask Concise Notes