Each clause consists of a list of comma-separated capability names (or the word `all'), followed by an action-list. An action-list consists of a sequence of operator flag pairs. Legal operators are: `=', '+', and `-'. Legal flags are: `e', `i', and `p'. These flags are case-sensitive and specify the Effective, Inheritable and Permitted sets respectively.
In the capability name lists, all names are case-insensitive. The special name `all' specifies all capabilities; it is equivalent to a list naming every capability individually.
Unnamed capabilities can also be specified by number. This feature ensures that libcap can support capabilities that were not allocated at the time libcap was compiled. However, generally upgrading libcap will add names for recently allocated capabilities.
The `=' operator indicates that the listed capabilities are first reset in all three capability sets. The subsequent flags (which are optional when associated with this operator) indicate that the listed capabilities for the corresponding set are to be raised. For example: "all=p" means lower every capability in the Effective and Inheritable sets but raise all of the Permitted capabilities; or, "cap_fowner=ep" means raise the Effective and Permitted override-file-ownership capability, while lowering this Inheritable capability.
In the case that the leading operator is `=', and no list of capabilities is provided, the action-list is assumed to refer to `all' capabilities. For example, the following three clauses are equivalent to each other (and indicate a completely empty capability set): "all="; "="; "cap_chown,<every-other-capability>=".
The operators, `+' and `-' both require an explicit preceding capability list and one or more explicit trailing flags. The `+' operator will raise all of the listed capabilities in the flagged capability sets. The `-' operator will lower all of the listed capabilities in the flagged capability sets. For example: "all+p" will raise all of the Permitted capabilities; "cap_fowner+p-i" will raise the override-file-ownership capability in the Permitted capability set and lower this Inheritable capability; "cap_fowner+pe-i" and "cap_fowner=+pe" are equivalent.