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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
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
144 or be directly preceded by a
147 On success 0 is returned and \-1 on failure.
151 function will return 0 if
153 is one of the names of the capability record
160 function searches the capability record
168 is specified using any single character.
169 If a colon (`:') is used, an
170 untyped capability will be searched for (see below for explanation of
172 A pointer to the value of
176 is returned on success,
178 if the requested capability could not be
180 The end of the capability value is signaled by a `:' or
183 (see below for capability database syntax).
187 function retrieves the value of the numeric capability
189 from the capability record pointed to by
191 The numeric value is returned in the
195 0 is returned on success, \-1 if the requested numeric capability could not
200 function retrieves the value of the string capability
202 from the capability record pointed to by
204 A pointer to a decoded,
208 copy of the string is returned in the
212 The number of characters in the decoded string not including the trailing
214 is returned on success, \-1 if the requested string capability could not
215 be found, \-2 if a system error was encountered (storage allocation
220 function is identical to
222 except that it does not expand special characters, but rather returns each
223 character of the capability string literally.
229 functions comprise a function group that provides for sequential
232 pointer terminated array of file names,
236 function returns the first record in the database and resets the access
240 function returns the next record in the database with respect to the
241 record returned by the previous
246 If there is no such previous call, the first record in the database is
248 Each record is returned in a
253 expansion is done (see
256 Upon completion of the database 0 is returned, 1 is returned upon successful
257 return of record with possibly more remaining (we have not reached the end of
258 the database yet), 2 is returned if the record contains an unresolved
260 expansion, \-1 is returned if a system error occurred, and \-2
261 is returned if a potential reference loop is detected (see
264 Upon completion of database (0 return) the database is closed.
268 function closes the sequential access and frees any memory and file descriptors
270 Note that it does not erase the buffer pushed by a call to
272 .Sh CAPABILITY DATABASE SYNTAX
273 Capability databases are normally
275 and may be edited with standard
277 Blank lines and lines beginning with a `#' are comments
279 Lines ending with a `\|\e' indicate that the next line
280 is a continuation of the current line; the `\|\e' and following newline
282 Long lines are usually continued onto several physical
283 lines by ending each line except the last with a `\|\e'.
285 Capability databases consist of a series of records, one per logical
287 Each record contains a variable number of `:'-separated fields
289 Empty fields consisting entirely of white space
290 characters (spaces and tabs) are ignored.
292 The first capability of each record specifies its names, separated by `|'
294 These names are used to reference records in the database.
295 By convention, the last name is usually a comment and is not intended as
303 .Dl "d0\||\|vt100\||\|vt100-am\||\|vt100am\||\|dec vt100:"
305 giving four names that can be used to access the record.
307 The remaining non-empty capabilities describe a set of (name, value)
308 bindings, consisting of a names optionally followed by a typed value:
310 .Bl -tag -width "nameTvalue" -compact
312 typeless [boolean] capability
313 .Em name No "is present [true]"
314 .It name Ns Em \&T Ns value
322 .It name Ns Em T Ns \&@
328 Names consist of one or more characters.
329 Names may contain any character
330 except `:', but it is usually best to restrict them to the printable
331 characters and avoid use of graphics like `#', `=', `%', `@', etc.
333 are single characters used to separate capability names from their
334 associated typed values.
335 Types may be any character except a `:'.
336 Typically, graphics like `#', `=', `%', etc.\& are used.
338 number of characters and may contain any character except `:'.
339 .Sh CAPABILITY DATABASE SEMANTICS
340 Capability records describe a set of (name, value) bindings.
342 have multiple values bound to them.
343 Different values for a name are
344 distinguished by their
348 function will return a pointer to a value of a name given the capability
349 name and the type of the value.
351 The types `#' and `=' are conventionally used to denote numeric and
352 string typed values, but no restriction on those types is enforced.
358 can be used to implement the traditional syntax and semantics of `#'
360 Typeless capabilities are typically used to denote boolean objects with
361 presence or absence indicating truth and false values respectively.
362 This interpretation is conveniently represented by:
364 .Dl "(getcap(buf, name, ':') != NULL)"
366 A special capability,
368 is used to indicate that the record specified by
370 should be substituted for the
374 capabilities may interpolate records which also contain
376 capabilities and more than one
378 capability may be used in a record.
381 expansion scope (i.e., where the argument is searched for) contains the
384 is declared and all subsequent files in the file array.
386 When a database is searched for a capability record, the first matching
387 record in the search is returned.
388 When a record is scanned for a
389 capability, the first matching capability is returned; the capability
391 will hide any following definition of a value of type
397 will prevent any following values of
401 These features combined with
403 capabilities can be used to generate variations of other databases and
404 records by either adding new capabilities, overriding definitions with new
405 definitions, or hiding following definitions via `@' capabilities.
407 .Bd -unfilled -offset indent
408 example\||\|an example of binding multiple values to names:\e
409 :foo%bar:foo^blah:foo@:\e
410 :abc%xyz:abc^frap:abc$@:\e
414 The capability foo has two values bound to it (bar of type `%' and blah of
415 type `^') and any other value bindings are hidden.
417 also has two values bound but only a value of type `$' is prevented from
418 being defined in the capability record more.
419 .Bd -unfilled -offset indent
421 new\||\|new_record\||\|a modification of "old":\e
422 :fript=bar:who-cares@:tc=old:blah:tc=extensions:
424 old\||\|old_record\||\|an old database record:\e
425 :fript=foo:who-cares:glork#200:
428 The records are extracted by calling
430 with file1 preceding file2.
431 In the capability record new in file1, fript=bar overrides the definition
432 of fript=foo interpolated from the capability record old in file2,
433 who-cares@ prevents the definition of any who-cares definitions in old
434 from being seen, glork#200 is inherited from old, and blah and anything
435 defined by the record extensions is added to those definitions in old.
436 Note that the position of the fript=bar and who-cares@ definitions before
437 tc=old is important here.
438 If they were after, the definitions in old
439 would take precedence.
440 .Sh CGETNUM AND CGETSTR SYNTAX AND SEMANTICS
441 Two types are predefined by
446 .Bl -tag -width "nameXnumber" -compact
447 .It Em name Ns \&# Ns Em number
452 .It Em name Ns = Ns Em string
458 the numeric capability
462 the string capability
467 Numeric capability values may be given in one of three numeric bases.
468 If the number starts with either
472 it is interpreted as a hexadecimal number (both upper and lower case a-f
473 may be used to denote the extended hexadecimal digits).
474 Otherwise, if the number starts with a
476 it is interpreted as an octal number.
477 Otherwise the number is interpreted as a decimal number.
479 String capability values may contain any character.
482 codes, new lines, and colons may be conveniently represented by the use
484 .Bl -column "\e\|X,X\e\|X" "(ASCII octal nnn)"
485 ^X ('X' & 037) control-X
486 \e\|b, \e\|B (ASCII 010) backspace
487 \e\|t, \e\|T (ASCII 011) tab
488 \e\|n, \e\|N (ASCII 012) line feed (newline)
489 \e\|f, \e\|F (ASCII 014) form feed
490 \e\|r, \e\|R (ASCII 015) carriage return
491 \e\|e, \e\|E (ASCII 027) escape
492 \e\|c, \e\|C (:) colon
493 \e\|\e (\e\|) back slash
495 \e\|nnn (ASCII octal nnn)
498 A `\|\e' may be followed by up to three octal digits directly specifies
499 the numeric code for a character.
504 encoded, causes all sorts of problems and must be used with care since
506 are typically used to denote the end of strings; many applications
507 use `\e\|200' to represent a
521 return a value greater than or equal to 0 on success and a value less
525 function returns a character pointer on success and a
533 functions may fail and set
535 for any of the errors specified for the library functions:
554 No memory to allocate.
560 Colons (`:') cannot be used in names, types, or values.
562 There are no checks for
563 .Ic tc Ns = Ns Ic name
567 The buffer added to the database by a call to
569 is not unique to the database but is rather prepended to any database used.