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 com-
ments 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 '=' char-
acter. 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
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CFG(2) CFG(2)
'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 (having 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 constructs defined above.
init(path)
Init initialises the Cfg module, causing it to open and
parse the configuration file given by the path argu-
ment. 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 application
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
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