CFG(2)CFG(2)NAME
Cfg, Record, Tuple, Attr - configuration file parser
SYNOPSIS
include "cfg.m";
cfg := load Cfg Cfg->PATH;
Attr: adt {
name: string;
value: string;
};
Tuple: adt {
lnum: int;
attrs: list of Attr;
lookup: fn(t: self ref Tuple, name: string): string;
};
Record: adt {
tuples: list of ref Tuple;
lookup: fn(r: self ref Record, name: string)
: (string, ref Tuple);
};
init: fn(path: string): string;
lookup: fn(name: string): list of (string, ref Record);
getkeys: fn(): list of string;
DESCRIPTION
Cfg parses its configuration file format into a set of Records.
Each line of the configuration file is comprised of a tuple of
attributes. Comments are introduced by the '#' character and run to
the end of the input line. Empty lines and comments are ignored.
An attribute has a name followed by an optional value. The value is
specified by separating the name and value by an '=' character.
Attribute names and values are input words. A word is delimited by
spacing characters and the '=' character. If a word needs to include
any of these characters then the word may be quoted using single or
double quotes. The start and end quotes must be the same. The quoting
character may be included in the word by appearing twice.
Examples:
'a b c' yields a b c
"a b c" yields a b c
'a " c' yields a " c
'a '' c' yields a ' c
The name of the first attribute of a tuple is its key. The primary
tuple value is the value of its first attribute.
Tuples whose first attribute name appears at the start of a line (hav‐
ing no preceeding spacing characters) are treated as the start of a new
record. A record incorporates all tuples up to the start of the next
record. The record key is defined to be the name of its first
attribute. The primary record value is the value of the first
attribute.
The adt types Attr, Tuple and Record are direct analogues of the con‐
structs defined above.
init(path)
Init initialises the Cfg module, causing it to open and parse
the configuration file given by the path argument. If an error
is encountered in processing the file then an error string is
returned. If there are no errors init returns nil.
lookup(name)
Lookup returns the set of Records whose key matches the name
argument. The return value is a list of (primary record value,
record) pairs.
getkeys()
Getkeys returns a list of the record keys that appear in the
configuration file. Note that more than one record can have the
same key. Duplicate key names are not returned by getkeys().
record.lookup(name)
Returns the first tuple in record whose key matches name. The
return value is (primary tuple value, tuple). If no matching
tuple is found then the value (nil, nil) is returned. Note that
more than one tuple of the record could have a key that matches
name. Only the first matching tuple is returned. If an appli‐
cation makes use of multiple tuples with the same key then the
record.tuple list will have to be handled explicitly by the
application.
tuple.lookup(name)
Returns the first attribute in tuple whose name matches name.
The return value is the value of the attribute or nil if no
matching attribute was found.
SOURCE
/appl/lib/cfg.b
CFG(2)
