Operator Numeric Modes (GNU Coreutils 9.0)
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27.4 Operator Numeric Modes
An operator numeric mode is a numeric mode that is prefixed by a ‘-
’, ‘+
’, or ‘=
’ operator, which has the same interpretation as in symbolic modes. For example, ‘+440
’ enables read permission for the file’s owner and group, ‘-1
’ disables execute permission for other users, and ‘=600
’ clears all permissions except for enabling read-write permissions for the file’s owner. Operator numeric modes can be combined with symbolic modes by separating them with a comma; for example, ‘=0,u+r
’ clears all permissions except for enabling read permission for the file’s owner.
The commands ‘chmod =755 dir
’ and ‘chmod 755 dir
’ differ in that the former clears the directory dir
’s setuid and setgid bits, whereas the latter preserves them. See Directory Setuid and Setgid.
Operator numeric modes are a GNU extension.