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5 .\" Casey Leedom of Lawrence Livermore National Laboratory.
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31 .\" @(#)getcap.3 8.4 (Berkeley) 5/13/94
32 .\" $FreeBSD: src/lib/libc/gen/getcap.3,v 1.30 2007/02/11 18:14:49 maxim Exp $
48 .Nd capability database access routines
54 .Fn cgetent "char **buf" "char **db_array" "const char *name"
56 .Fn cgetset "const char *ent"
58 .Fn cgetmatch "const char *buf" "const char *name"
60 .Fn cgetcap "char *buf" "const char *cap" "int type"
62 .Fn cgetnum "char *buf" "const char *cap" "long *num"
64 .Fn cgetstr "char *buf" "const char *cap" "char **str"
66 .Fn cgetustr "char *buf" "const char *cap" "char **str"
68 .Fn cgetfirst "char **buf" "char **db_array"
70 .Fn cgetnext "char **buf" "char **db_array"
76 function extracts the capability
78 from the database specified by the
82 and returns a pointer to a
88 function will first look for files ending in
92 before accessing the ASCII file.
96 must be retained through all subsequent calls to
105 On success 0 is returned, 1 if the returned
106 record contains an unresolved
109 \-1 if the requested record could not be found,
110 \-2 if a system error was encountered (could not open/read a file, etc.) also
113 and \-3 if a potential reference loop is detected (see
119 function enables the addition of a character buffer containing a single capability
121 to the capability database.
122 Conceptually, the entry is added as the first ``file'' in the database, and
123 is therefore searched first on the call to
125 The entry is passed in
131 the current entry is removed from the database.
134 must precede the database traversal.
135 It must be called before the
138 If a sequential access is being performed (see below), it must be called
139 before the first sequential access call
143 or be directly preceded by a
146 On success 0 is returned and \-1 on failure.
150 function will return 0 if
152 is one of the names of the capability record
159 function searches the capability record
167 is specified using any single character.
168 If a colon (`:') is used, an
169 untyped capability will be searched for (see below for explanation of
171 A pointer to the value of
175 is returned on success,
177 if the requested capability could not be
179 The end of the capability value is signaled by a `:' or
182 (see below for capability database syntax).
186 function retrieves the value of the numeric capability
188 from the capability record pointed to by
190 The numeric value is returned in the
194 0 is returned on success, \-1 if the requested numeric capability could not
199 function retrieves the value of the string capability
201 from the capability record pointed to by
203 A pointer to a decoded,
207 copy of the string is returned in the
211 The number of characters in the decoded string not including the trailing
213 is returned on success, \-1 if the requested string capability could not
214 be found, \-2 if a system error was encountered (storage allocation
219 function is identical to
221 except that it does not expand special characters, but rather returns each
222 character of the capability string literally.
228 functions comprise a function group that provides for sequential
231 pointer terminated array of file names,
235 function returns the first record in the database and resets the access
239 function returns the next record in the database with respect to the
240 record returned by the previous
245 If there is no such previous call, the first record in the database is
247 Each record is returned in a
252 expansion is done (see
255 Upon completion of the database 0 is returned, 1 is returned upon successful
256 return of record with possibly more remaining (we have not reached the end of
257 the database yet), 2 is returned if the record contains an unresolved
259 expansion, \-1 is returned if a system error occurred, and \-2
260 is returned if a potential reference loop is detected (see
263 Upon completion of database (0 return) the database is closed.
267 function closes the sequential access and frees any memory and file descriptors
269 Note that it does not erase the buffer pushed by a call to
283 return a value greater than or equal to 0 on success and a value less
287 function returns a character pointer on success and a
290 .Sh CAPABILITY DATABASE SYNTAX
291 Capability databases are normally
293 and may be edited with standard
295 Blank lines and lines beginning with a `#' are comments
297 Lines ending with a `\|\e' indicate that the next line
298 is a continuation of the current line; the `\|\e' and following newline
300 Long lines are usually continued onto several physical
301 lines by ending each line except the last with a `\|\e'.
303 Capability databases consist of a series of records, one per logical
305 Each record contains a variable number of `:'-separated fields
307 Empty fields consisting entirely of white space
308 characters (spaces and tabs) are ignored.
310 The first capability of each record specifies its names, separated by `|'
312 These names are used to reference records in the database.
313 By convention, the last name is usually a comment and is not intended as
321 .Dl "d0\||\|vt100\||\|vt100-am\||\|vt100am\||\|dec vt100:"
323 giving four names that can be used to access the record.
325 The remaining non-empty capabilities describe a set of (name, value)
326 bindings, consisting of a names optionally followed by a typed value:
327 .Bl -column "nameTvalue"
328 .It name Ta "typeless [boolean] capability"
329 .Em name No "is present [true]"
330 .It name Ns Em \&T Ns value Ta capability
334 .It name@ Ta "no capability" Em name No exists
335 .It name Ns Em T Ns \&@ Ta capability
340 Names consist of one or more characters.
341 Names may contain any character
342 except `:', but it is usually best to restrict them to the printable
343 characters and avoid use of graphics like `#', `=', `%', `@', etc.
345 are single characters used to separate capability names from their
346 associated typed values.
347 Types may be any character except a `:'.
348 Typically, graphics like `#', `=', `%', etc.\& are used.
350 number of characters and may contain any character except `:'.
351 .Sh CAPABILITY DATABASE SEMANTICS
352 Capability records describe a set of (name, value) bindings.
353 Names may have multiple values bound to them.
354 Different values for a name are
355 distinguished by their
359 function will return a pointer to a value of a name given the capability
360 name and the type of the value.
362 The types `#' and `=' are conventionally used to denote numeric and
363 string typed values, but no restriction on those types is enforced.
369 can be used to implement the traditional syntax and semantics of `#'
371 Typeless capabilities are typically used to denote boolean objects with
372 presence or absence indicating truth and false values respectively.
373 This interpretation is conveniently represented by:
375 .Dl "(getcap(buf, name, ':') != NULL)"
377 A special capability,
379 is used to indicate that the record specified by
381 should be substituted for the
385 capabilities may interpolate records which also contain
387 capabilities and more than one
389 capability may be used in a record.
392 expansion scope (i.e., where the argument is searched for) contains the
395 is declared and all subsequent files in the file array.
397 When a database is searched for a capability record, the first matching
398 record in the search is returned.
399 When a record is scanned for a
400 capability, the first matching capability is returned; the capability
402 will hide any following definition of a value of type
408 will prevent any following values of
412 These features combined with
414 capabilities can be used to generate variations of other databases and
415 records by either adding new capabilities, overriding definitions with new
416 definitions, or hiding following definitions via `@' capabilities.
418 .Bd -unfilled -offset indent
419 example\||\|an example of binding multiple values to names:\e
420 :foo%bar:foo^blah:foo@:\e
421 :abc%xyz:abc^frap:abc$@:\e
425 The capability foo has two values bound to it (bar of type `%' and blah of
426 type `^') and any other value bindings are hidden.
428 also has two values bound but only a value of type `$' is prevented from
429 being defined in the capability record more.
430 .Bd -unfilled -offset indent
432 new\||\|new_record\||\|a modification of "old":\e
433 :fript=bar:who-cares@:tc=old:blah:tc=extensions:
435 old\||\|old_record\||\|an old database record:\e
436 :fript=foo:who-cares:glork#200:
439 The records are extracted by calling
441 with file1 preceding file2.
442 In the capability record new in file1, fript=bar overrides the definition
443 of fript=foo interpolated from the capability record old in file2,
444 who-cares@ prevents the definition of any who-cares definitions in old
445 from being seen, glork#200 is inherited from old, and blah and anything
446 defined by the record extensions is added to those definitions in old.
447 Note that the position of the fript=bar and who-cares@ definitions before
448 tc=old is important here.
449 If they were after, the definitions in old
450 would take precedence.
451 .Sh CGETNUM AND CGETSTR SYNTAX AND SEMANTICS
452 Two types are predefined by
456 .Bl -column "nameXnumber"
458 .It Em name No \&# Em number Ta numeric
465 .It Em name No = Em string Ta "string capability"
471 .It Em name No \&#@ Ta "the numeric capability"
476 .It Em name No \&=@ Ta "the string capability"
482 Numeric capability values may be given in one of three numeric bases.
483 If the number starts with either
487 it is interpreted as a hexadecimal number (both upper and lower case a-f
488 may be used to denote the extended hexadecimal digits).
489 Otherwise, if the number starts with a
491 it is interpreted as an octal number.
492 Otherwise the number is interpreted as a decimal number.
494 String capability values may contain any character.
497 codes, new lines, and colons may be conveniently represented by the use
499 .Bl -column "\e\|X,X\e\|X" "(ASCII octal nnn)"
500 ^X ('X' & 037) control-X
501 \e\|b, \e\|B (ASCII 010) backspace
502 \e\|t, \e\|T (ASCII 011) tab
503 \e\|n, \e\|N (ASCII 012) line feed (newline)
504 \e\|f, \e\|F (ASCII 014) form feed
505 \e\|r, \e\|R (ASCII 015) carriage return
506 \e\|e, \e\|E (ASCII 027) escape
507 \e\|c, \e\|C (:) colon
508 \e\|\e (\e\|) back slash
510 \e\|nnn (ASCII octal nnn)
513 A `\|\e' may be followed by up to three octal digits directly specifies
514 the numeric code for a character.
519 encoded, causes all sorts of problems and must be used with care since
521 are typically used to denote the end of strings; many applications
522 use `\e\|200' to represent a
529 functions may fail and set
531 for any of the errors specified for the library functions:
550 No memory to allocate.
556 Colons (`:') cannot be used in names, types, or values.
558 There are no checks for
559 .Ic tc Ns = Ns Ic name
563 The buffer added to the database by a call to
565 is not unique to the database but is rather prepended to any database used.