cgetcap(3) - NetBSD Manual Pages

CGETCAP(3)              NetBSD Library Functions Manual             CGETCAP(3)


NAME

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


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <stdlib.h>

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

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

     int
     cgetclose(void);

     void
     csetexpandtc(int expandtc);


DESCRIPTION

     cgetent() 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.  cgetent() will first look for files end-
     ing in .db (see cap_mkdb(1)) before accessing the ASCII file.

     buf 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 couldn't be found, -2 if a
     system error was encountered (couldn't open/read a file, etc.)  also set-
     ting errno, and -3 if a potential reference loop is detected (see
     "tc=name" comments below).

     cgetset() enables the addition of a character buffer containing 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.

     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 sequential access call
     (cgetfirst() or cgetnext()), or be directly preceded by a cgetclose()
     call.  On success 0 is returned and -1 on failure.

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

     cgetcap() searches the capability record buf for the capability cap with
     type type.  A type is specified using any single character.  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 couldn't be found.  The end
     of the capability value is signaled by a `:'.  See capfile(5) for a
     description of the capability syntax.

     cgetnum() 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 couldn't be found.

     cgetstr() retrieves the value of the string capability cap from the capa-
     bility 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 capabil-
     ity couldn't be found, -2 if a system error was encountered (storage
     allocation failure).

     cgetustr() is identical to cgetstr() except that it does not expand spe-
     cial characters, but rather returns each character of the capability
     string literally.

     cgetfirst(), cgetnext(), comprise a function group that provides for
     sequential access of the NULL pointer terminated array of file names,
     db_array.  cgetfirst() returns the first record in the database and
     resets the access to the first record.  cgetnext() returns the next
     record in the database with respect to the record returned by the previ-
     ous 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=name" comments below).

     Upon completion of the database 0 is returned,  1 is returned upon suc-
     cessful return of record with possibly more remaining (we haven't reached
     the end of the database yet), 2 is returned if the record contains an
     unresolved "tc" expansion, -1 is returned if an system error occurred,
     and -2 is returned if a potential reference loop is detected (see
     "tc=name" comments below).  Upon completion of database (0 return) the
     database is closed.

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


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.  cgetcap() 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
     specified by name should be substituted for the "tc" capability.  "tc"
     capabilities may interpolate records which also contain "tc" capabilities
     and more than one "tc" capability may be used in a record.  A "tc" expan-
     sion 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.

     csetexpandtc() can be used to control if "tc" expansion is performed or
     not.


RETURN VALUES

     cgetent(), cgetset(), cgetmatch(), cgetnum(), cgetstr(), cgetustr(),
     cgetfirst(), and cgetnext() return a value greater than or equal to 0 on
     success and a value less than 0 on failure.  cgetcap() returns a charac-
     ter pointer on success and a NULL on failure.

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

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

     [ENOMEM]           No memory to allocate.


SEE ALSO

     cap_mkdb(1), malloc(3), capfile(5)


BUGS

     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.

NetBSD 10.99                     April 5, 2012                    NetBSD 10.99