NAME
cgetent,
cgetset,
cgetmatch,
cgetcap,
cgetnum,
cgetstr,
cgetustr,
cgetfirst,
cgetnext,
cgetclose,
cexpandtc —
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 ending 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
setting
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 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 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 special 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
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=name” comments below).
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
“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 distinguished
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 traditional syntax
and semantics of ‘#’ and ‘=’. 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:
(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”
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.
csetexpandtc() can be used to control if “tc”
expansion is performed or not.
DIAGNOSTICS
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 character 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.