Provided by: libcap-dev_1.10-14build1_i386
cap_from_text, cap_to_text, _cap_names - capability state textual
cap_t cap_from_text(const char *buf_p);
char *cap_to_text(cap_t caps, ssize_t *length_p);
extern char const *_cap_names;
cc ... -lcap
These functions translate a capability state from an internal
representation into a textual one. The internal representation is
managed by the capability functions in working storage. The textual
representation is a structured, human-readable, string suitable for
cap_from_text allocates and initializes a capability state in working
storage. It then sets the contents of this newly-created capability
state to the state represented by human-readable, null terminated
character string pointed to by buf_p. It returns a pointer to the
newly created capability state. The caller should free any releasable
memory, when the capability state in working storage is no longer
required, by calling cap_free with cap_t as an argument. The function
returns an error if it cannot parse the contents of the string pointed
to by buf_p or does not recognize any capability_name or flag character
as valid. The function also returns an error if any flag is both set
and cleared within a single clause.
cap_to_text converts the capability state in working storage identified
by cap_p into a null terminated human-readable string. This function
allocates any memory necessary to contain the string, and returns a
pointer to the string. If the pointer len_p is not NULL, the function
shall also return the full length of the string (not including the null
terminator) in the location pointed to by len_p. The capability state
in working storage, identified by cap_p, is completely represented in
the character string. The caller should free any releasable memory,
when the capability state in working storage is no longer required, by
calling cap_free with cap_p as an argument.
_cap_names is an array of textual names for capability numbers.
Unnamed capabilities have a NULL entry. (This array is not defined by
A textual representation of capability sets consists of one or more
whitespace-separated clauses. Each clause specifies some operations to
a capability set; the set starts out with all capabilities lowered, and
the meaning of the string is the state of the capability set after all
the clauses have been applied in order.
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
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.
Although not defined by POSIX, unnamed capabilities can be specified by
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=";
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.
cap_from_text and cap_to_text return a non-NULL value on success, and
NULL on failure.
On failure, errno(3) is set to EINVAL, or ENOMEM.
cap_from_text and cap_to_text are specified by POSIX.1e. _cap_names is
a Linux extension.
cap_clear(3), cap_copy_ext(3), cap_get_file(3), cap_get_proc(3),
26th May 1997 CAP_FROM_TEXT(3)