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GETCAP(3)	       FreeBSD Library Functions Manual		     GETCAP(3)

NAME
     cgetent, cgetset, cgetmatch, cgetcap, cgetnum, cgetstr, cgetustr,
     cgetfirst,	cgetnext, cgetclose -- capability database access routines

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     int
     cgetent(char **buf, char **db_array, const	char *name);

     int
     cgetset(const char	*ent);

     int
     cgetmatch(const char *buf,	const char *name);

     char *
     cgetcap(char *buf,	const char *cap, int type);

     int
     cgetnum(char *buf,	const char *cap, long *num);

     int
     cgetstr(char *buf,	const char *cap, char **str);

     int
     cgetustr(char *buf, const char *cap, char **str);

     int
     cgetfirst(char **buf, char	**db_array);

     int
     cgetnext(char **buf, char **db_array);

     int
     cgetclose(void);

DESCRIPTION
     The cgetent() function extracts the capability name from the database
     specified by the NULL terminated file array db_array and returns a
     pointer to	a malloc(3)'d copy of it in buf.  The cgetent()	function will
     first look	for files ending in .db	(see cap_mkdb(1)) before accessing the
     ASCII file.  The buf argument must	be retained through all	subsequent
     calls to cgetmatch(), cgetcap(), cgetnum(), cgetstr(), and	cgetustr(),
     but may then be free(3)'d.	 On success 0 is returned, 1 if	the returned
     record contains an	unresolved tc expansion, -1 if the requested record
     could not be found, -2 if a system	error was encountered (could not
     open/read a file, etc.) also setting errno, and -3	if a potential refer-
     ence loop is detected (see	tc= comments below).

     The cgetset() function enables the	addition of a character	buffer con-
     taining a single capability record	entry to the capability	database.
     Conceptually, the entry is	added as the first ``file'' in the database,
     and is therefore searched first on	the call to cgetent().	The entry is
     passed in ent.  If	ent is NULL, the current entry is removed from the
     database.	A call to cgetset() must precede the database traversal.  It
     must be called before the cgetent() call.	If a sequential	access is
     being performed (see below), it must be called before the first sequen-
     tial access call (cgetfirst() or cgetnext()), or be directly preceded by
     a cgetclose() call.  On success 0 is returned and -1 on failure.

     The cgetmatch() function will return 0 if name is one of the names	of the
     capability	record buf, -1 if not.

     The cgetcap() function searches the capability record buf for the capa-
     bility cap	with type type.	 A type	is specified using any single charac-
     ter.  If a	colon (`:') is used, an	untyped	capability will	be searched
     for (see below for	explanation of types).	A pointer to the value of cap
     in	buf is returned	on success, NULL if the	requested capability could not
     be	found.	The end	of the capability value	is signaled by a `:' or	ASCII
     NUL (see below for	capability database syntax).

     The cgetnum() function retrieves the value	of the numeric capability cap
     from the capability record	pointed	to by buf.  The	numeric	value is
     returned in the long pointed to by	num.  0	is returned on success,	-1 if
     the requested numeric capability could not	be found.

     The cgetstr() function retrieves the value	of the string capability cap
     from the capability record	pointed	to by buf.  A pointer to a decoded,
     NUL terminated, malloc(3)'d copy of the string is returned	in the char *
     pointed to	by str.	 The number of characters in the decoded string	not
     including the trailing NUL	is returned on success,	-1 if the requested
     string capability could not be found, -2 if a system error	was encoun-
     tered (storage allocation failure).

     The cgetustr() function is	identical to cgetstr() except that it does not
     expand special characters,	but rather returns each	character of the capa-
     bility string literally.

     The cgetfirst() and cgetnext() functions comprise a function group	that
     provides for sequential access of the NULL	pointer	terminated array of
     file names, db_array.  The	cgetfirst() function returns the first record
     in	the database and resets	the access to the first	record.	 The
     cgetnext()	function returns the next record in the	database with respect
     to	the record returned by the previous cgetfirst()	or cgetnext() call.
     If	there is no such previous call,	the first record in the	database is
     returned.	Each record is returned	in a malloc(3)'d copy pointed to by
     buf.  Tc expansion	is done	(see tc= comments below).  Upon	completion of
     the database 0 is returned, 1 is returned upon successful return of
     record with possibly more remaining (we have not reached the end of the
     database yet), 2 is returned if the record	contains an unresolved tc
     expansion,	-1 is returned if a system error occurred, and -2 is returned
     if	a potential reference loop is detected (see tc=	comments below).  Upon
     completion	of database (0 return) the database is closed.

     The cgetclose() function closes the sequential access and frees any mem-
     ory and file descriptors being used.  Note	that it	does not erase the
     buffer pushed by a	call to	cgetset().

CAPABILITY DATABASE SYNTAX
     Capability	databases are normally ASCII and may be	edited with standard
     text editors.  Blank lines	and lines beginning with a `#' are comments
     and are ignored.  Lines ending with a `\' indicate	that the next line is
     a continuation of the current line; the `\' and following newline are
     ignored.  Long lines are usually continued	onto several physical lines by
     ending each line except the last with a `\'.

     Capability	databases consist of a series of records, one per logical
     line.  Each record	contains a variable number of `:'-separated fields
     (capabilities).  Empty fields consisting entirely of white	space charac-
     ters (spaces and tabs) are	ignored.

     The first capability of each record specifies its names, separated	by `|'
     characters.  These	names are used to reference records in the database.
     By	convention, the	last name is usually a comment and is not intended as
     a lookup tag.  For	example, the vt100 record from the termcap(5) database
     begins:

	   d0|vt100|vt100-am|vt100am|dec vt100:

     giving four names that can	be used	to access the record.

     The remaining non-empty capabilities describe a set of (name, value)
     bindings, consisting of a names optionally	followed by a typed value:

     name	 typeless [boolean] capability name is present [true]
     nameTvalue	 capability (name, T) has value	value
     name@	 no capability name exists
     nameT@	 capability (name, T) does not exist

     Names consist of one or more characters.  Names may contain any character
     except `:', but it	is usually best	to restrict them to the	printable
     characters	and avoid use of graphics like `#', `=', `%', `@', etc.	 Types
     are single	characters used	to separate capability names from their	asso-
     ciated typed values.  Types may be	any character except a `:'.  Typi-
     cally, graphics like `#', `=', `%', etc. are used.	 Values	may be any
     number of characters and may contain any character	except `:'.

CAPABILITY DATABASE SEMANTICS
     Capability	records	describe a set of (name, value)	bindings.  Names may
     have multiple values bound	to them.  Different values for a name are dis-
     tinguished	by their types.	 The cgetcap() function	will return a pointer
     to	a value	of a name given	the capability name and	the type of the	value.

     The types `#' and `=' are conventionally used to denote numeric and
     string typed values, but no restriction on	those types is enforced.  The
     functions cgetnum() and cgetstr() can be used to implement	the tradi-
     tional syntax and semantics of `#'	and `='.  Typeless capabilities	are
     typically used to denote boolean objects with presence or absence indi-
     cating truth and false values respectively.  This interpretation is con-
     veniently represented by:

	   (getcap(buf,	name, ':') != NULL)

     A special capability, tc= name, is	used to	indicate that the record spec-
     ified by name should be substituted for the tc capability.	 Tc capabili-
     ties may interpolate records which	also contain tc	capabilities and more
     than one tc capability may	be used	in a record.  A	tc expansion scope
     (i.e., where the argument is searched for)	contains the file in which the
     tc	is declared and	all subsequent files in	the file array.

     When a database is	searched for a capability record, the first matching
     record in the search is returned.	When a record is scanned for a capa-
     bility, the first matching	capability is returned;	the capability
     :nameT@: will hide	any following definition of a value of type T for
     name; and the capability :name@: will prevent any following values	of
     name from being seen.

     These features combined with tc capabilities can be used to generate
     variations	of other databases and records by either adding	new capabili-
     ties, overriding definitions with new definitions,	or hiding following
     definitions via `@' capabilities.

EXAMPLES
	   example|an example of binding multiple values to names:\
		:foo%bar:foo^blah:foo@:\
		:abc%xyz:abc^frap:abc$@:\
		:tc=more:

     The capability foo	has two	values bound to	it (bar	of type	`%' and	blah
     of	type `^') and any other	value bindings are hidden.  The	capability abc
     also has two values bound but only	a value	of type	`$' is prevented from
     being defined in the capability record more.

	   file1:
		new|new_record|a modification of "old":\
		     :fript=bar:who-cares@:tc=old:blah:tc=extensions:
	   file2:
		old|old_record|an old database record:\
		     :fript=foo:who-cares:glork#200:

     The records are extracted by calling cgetent() with file1 preceding
     file2.  In	the capability record new in file1, fript=bar overrides	the
     definition	of fript=foo interpolated from the capability record old in
     file2, who-cares@ prevents	the definition of any who-cares	definitions in
     old from being seen, glork#200 is inherited from old, and blah and	any-
     thing defined by the record extensions is added to	those definitions in
     old.  Note	that the position of the fript=bar and who-cares@ definitions
     before tc=old is important	here.  If they were after, the definitions in
     old would take precedence.

CGETNUM	AND CGETSTR SYNTAX AND SEMANTICS
     Two types are predefined by cgetnum() and cgetstr():

     name#number  numeric capability name has value number
     name=string  string capability name has value string
     name#@	  the numeric capability name does not exist
     name=@	  the string capability	name does not exist

     Numeric capability	values may be given in one of three numeric bases.  If
     the number	starts with either `0x'	or `0X'	it is interpreted as a hexa-
     decimal number (both upper	and lower case a-f may be used to denote the
     extended hexadecimal digits).  Otherwise, if the number starts with a `0'
     it	is interpreted as an octal number.  Otherwise the number is inter-
     preted as a decimal number.

     String capability values may contain any character.  Non-printable	ASCII
     codes, new	lines, and colons may be conveniently represented by the use
     of	escape sequences:

     ^X	       ('X' & 037)	    control-X
     \b, \B    (ASCII 010)	    backspace
     \t, \T    (ASCII 011)	    tab
     \n, \N    (ASCII 012)	    line feed (newline)
     \f, \F    (ASCII 014)	    form feed
     \r, \R    (ASCII 015)	    carriage return
     \e, \E    (ASCII 027)	    escape
     \c, \C    (:)		    colon
     \\	       (\)		    back slash
     \^	       (^)		    caret
     \nnn      (ASCII octal nnn)

     A `\' may be followed by up to three octal	digits directly	specifies the
     numeric code for a	character.  The	use of ASCII NULs, while easily
     encoded, causes all sorts of problems and must be used with care since
     NULs are typically	used to	denote the end of strings; many	applications
     use `\200'	to represent a NUL.

DIAGNOSTICS
     The cgetent(), cgetset(), cgetmatch(), cgetnum(), cgetstr(), cgetustr(),
     cgetfirst(), and cgetnext() functions return a value greater than or
     equal to 0	on success and a value less than 0 on failure.	The cgetcap()
     function returns a	character pointer on success and a NULL	on failure.

     The cgetent(), and	cgetset() functions may	fail and set errno for any of
     the errors	specified for the library functions: fopen(3), fclose(3),
     open(2), and close(2).

     The cgetent(), cgetset(), cgetstr(), and cgetustr() functions may fail
     and set errno as follows:

     [ENOMEM]		No memory to allocate.

SEE ALSO
     cap_mkdb(1), malloc(3)

BUGS
     Colons (`:') cannot be used in names, types, or values.

     There are no checks for tc=name loops in cgetent().

     The buffer	added to the database by a call	to cgetset() is	not unique to
     the database but is rather	prepended to any database used.

FreeBSD	9.2			March 22, 2002			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | CAPABILITY DATABASE SYNTAX | CAPABILITY DATABASE SEMANTICS | EXAMPLES | CGETNUM AND CGETSTR SYNTAX AND SEMANTICS | DIAGNOSTICS | SEE ALSO | BUGS

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