Info Catalog coreutils: Numeric Modes coreutils: File permissions coreutils: Directory Setuid and Setgid

coreutils: Operator Numeric Modes

 
 26.4 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.  Directory Setuid and Setgid.
 
    Operator numeric modes are a GNU extension.
 

Info Catalog coreutils: Numeric Modes coreutils: File permissions coreutils: Directory Setuid and Setgid