Provided by: libcap-dev_1.10-14build1_i386 bug

NAME

       cap_from_text,  cap_to_text,  _cap_names  -  capability  state  textual
       representation translation

SYNOPSIS

       #include <sys/capability.h>

       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[];

USAGE

       cc ... -lcap

DESCRIPTION

       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
       display.

       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
       POSIX.1e.)

TEXTUAL REPRESENTATION

       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
       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.

       Although not defined by POSIX, unnamed capabilities can be specified by
       number.

       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.

RETURN VALUE

       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.

CONFORMING TO

       cap_from_text and cap_to_text are specified by POSIX.1e.  _cap_names is
       a Linux extension.

SEE ALSO

       cap_clear(3),   cap_copy_ext(3),   cap_get_file(3),    cap_get_proc(3),
       cap_init(3)

                                 26th May 1997                CAP_FROM_TEXT(3)