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\"      @(#)getcap.3    8.4 (Berkeley) 5/13/94
\"
Dd April 5, 2012
Dt CGETCAP 3
Os
Sh NAME
Nm cgetent ,
Nm cgetset ,
Nm cgetmatch ,
Nm cgetcap ,
Nm cgetnum ,
Nm cgetstr ,
Nm cgetustr ,
Nm cgetfirst ,
Nm cgetnext ,
Nm cgetclose ,
Nm csetexpandtc
Nd capability database access routines
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In stdlib.h
Ft int
Fn cgetent "char **buf" "const char * const *db_array" "const char *name"
Ft int
Fn cgetset "const char *ent"
Ft int
Fn cgetmatch "const char *buf" "const char *name"
Ft char *
Fn cgetcap "char *buf" "const char *cap" "int type"
Ft int
Fn cgetnum "char *buf" "const char *cap" "long *num"
Ft int
Fn cgetstr "char *buf" "const char *cap" "char **str"
Ft int
Fn cgetustr "char *buf" "const char *cap" "char **str"
Ft int
Fn cgetfirst "char **buf" "const char * const *db_array"
Ft int
Fn cgetnext "char **buf" "const char * const *db_array"
Ft int
Fn cgetclose "void"
Ft void
Fn csetexpandtc "int expandtc"
Sh DESCRIPTION
Fn cgetent
extracts the capability
Fa name
from the database specified by the
Dv NULL
terminated file array
Fa db_array
and returns a pointer to a
Xr malloc 3 Ap d
copy of it in
Fa buf .
Fn cgetent
will first look for files ending in
Pa .db
(see
Xr cap_mkdb 1 )
before accessing the
Tn ASCII
file.
Pp
Fa buf
must be retained through all subsequent calls to
Fn cgetmatch ,
Fn cgetcap ,
Fn cgetnum ,
Fn cgetstr ,
and
Fn cgetustr ,
but may then be
Xr free 3 Ap d .
Pp
On success 0 is returned, 1 if the returned record contains an unresolved
Qq 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 setting
Va errno ,
and \-3 if a potential reference loop is detected (see
Qq tc=name
comments below).
Pp
Fn 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
Dq file
in the database, and
is therefore searched first on the call to
Fn cgetent .
The entry is passed in
Fa ent .
If
Fa ent
is
Dv NULL ,
the current entry is removed from the database.
Pp
Fn cgetset
must precede the database traversal.
It must be called before the
Fn cgetent
call.
If a sequential access is being performed (see below), it must be called
before the first sequential access call
Po
Fn cgetfirst
or
Fn cgetnext
Pc ,
or be directly preceded by a
Fn cgetclose
call.
On success 0 is returned and \-1 on failure.
Pp
Fn cgetmatch
will return 0 if
Fa name
is one of the names of the capability record
Fa buf ,
\-1 if not.
Pp
Fn cgetcap
searches the capability record
Fa buf
for the capability
Fa cap
with type
Fa type .
A
Fa type
is specified using any single character.
If a colon
Pq Sq \&:
is used, an untyped capability will be searched
for (see below for explanation of types).
A pointer to the value of
Fa cap
in
Fa buf
is returned on success,
Dv NULL
if the requested capability couldn't be found.
The end of the capability value is signaled by a
Sq \&: .
See
Xr capfile 5
for a description of the capability syntax.
Pp
Fn cgetnum
retrieves the value of the numeric capability
Fa cap
from the capability record pointed to by
Fa buf .
The numeric value is returned in the
Ft long
pointed to by
Fa num .
0 is returned on success,
\-1 if the requested numeric capability couldn't be found.
Pp
Fn cgetstr
retrieves the value of the string capability
Fa cap
from the capability record pointed to by
Fa buf .
A pointer to a decoded,
Dv NUL
terminated,
Xr malloc 3 Ap d
copy of the string is returned in the
Ft char *
pointed to by
Fa str .
The number of characters in the decoded string not including the trailing
Dv NUL
is returned on success, \-1 if the requested string capability couldn't
be found, \-2 if a system error was encountered (storage allocation
failure).
Pp
Fn cgetustr
is identical to
Fn cgetstr
except that it does not expand special characters, but rather returns each
character of the capability string literally.
Pp
Fn cgetfirst ,
Fn cgetnext ,
comprise a function group that provides for sequential access of the
Dv NULL
pointer terminated array of file names,
Fa db_array .
Fn cgetfirst
returns the first record in the database and resets the access
to the first record.
Fn cgetnext
returns the next record in the database with respect to the
record returned by the previous
Fn cgetfirst
or
Fn cgetnext
call.
If there is no such previous call,
the first record in the database is returned.
Each record is returned in a
Xr malloc 3 Ap d
copy pointed to by
Fa buf .
Qq tc
expansion is done (see
Qq tc=name
comments below).
Pp
Upon completion of the database 0 is returned,  1 is returned upon successful
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
Qq tc
expansion, \-1 is returned if an system error occurred, and \-2
is returned if a potential reference loop is detected (see
Qq tc=name
comments below).
Upon completion of database (0 return) the database is closed.
Pp
Fn 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
Fn cgetset .
Sh 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 distinguished by their
Fa types .
Fn cgetcap
will return a pointer to a value of a name given the capability name and
the type of the value.
Pp
The types
Sq #
and
Sq =
are conventionally used to denote numeric and
string typed values, but no restriction on those types is enforced.
The functions
Fn cgetnum
and
Fn cgetstr
can be used to implement the traditional syntax and semantics of
Sq #
and
Sq = .
Typeless capabilities are typically used to denote boolean objects with
presence or absence indicating truth and false values respectively.
This interpretation is conveniently represented by:
Pp
Dl "(getcap(buf, name, ':') != NULL)"
Pp
A special capability,
Qq tc=name ,
is used to indicate that the record specified by
Fa name
should be substituted for the
Qq tc
capability.
Qq tc
capabilities may interpolate records which also contain
Qq tc
capabilities and more than one
Qq tc
capability may be used in a record.
A
Qq tc
expansion scope (i.e. where the argument is searched for) contains the
file in which the
Qq tc
is declared and all subsequent files in the file array.
Pp
Fn csetexpandtc
can be used to control if
Qq tc
expansion is performed or not.
Sh RETURN VALUES
Fn cgetent ,
Fn cgetset ,
Fn cgetmatch ,
Fn cgetnum ,
Fn cgetstr ,
Fn cgetustr ,
Fn cgetfirst ,
and
Fn cgetnext
return a value greater than or equal to 0 on success and a value less
than 0 on failure.
Fn cgetcap
returns a character pointer on success and a
Dv NULL
on failure.
Pp
Fn cgetclose ,
Fn cgetent ,
Fn cgetfirst ,
and
Fn cgetnext
may fail and set
Va errno
for any of the errors specified for the library functions:
Xr fopen 3 ,
Xr fclose 3 ,
Xr open 2 ,
and
Xr close 2 .
Pp
Fn cgetent ,
Fn cgetset ,
Fn cgetstr ,
and
Fn cgetustr
may fail and set
Va errno
as follows:
Bl -tag -width Er
It Bq Er ENOMEM
No memory to allocate.
El
Sh SEE ALSO
Xr cap_mkdb 1 ,
Xr malloc 3 ,
Xr capfile 5
Sh BUGS
There are no checks for
Qq tc=name
loops in
Fn cgetent .
Pp
The buffer added to the database by a call to
Fn cgetset
is not unique to the database but is rather prepended to any database used.

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