ref: 84989770721391018dd6a247831cb79a43c1d86b
dir: /man/2/cfg/
.TH CFG 2
.SH NAME
Cfg, Record, Tuple, Attr \- configuration file parser
.SH SYNOPSIS
.EX
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;
.EE
.SH DESCRIPTION
.B Cfg
parses its configuration file format into a set of
.BR Record s.
.PP
Each line of the configuration file is comprised of a tuple of attributes.
Comments are introduced by the
.RB ' # '
character and run to the end of the input line.
Empty lines and comments are ignored.
.PP
An attribute has a name followed by an optional value.
The value is specified by separating the name and value
by an
.RB ' = '
character.
Attribute names and values are input
.IR words .
A word is delimited by spacing characters and the
.RB ' = '
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.
.PP
Examples:
.EX
'a b c' yields a b c
"a b c" yields a b c
'a " c' yields a " c
'a '' c' yields a ' c
.EE
.PP
The name of the first attribute of a tuple is its
.IR key .
The
.I primary tuple value
is the value of its first attribute.
.PP
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
.I record key
is defined to be the name of its first attribute.
The
.I primary record value
is the value of the first attribute.
.PP
The
.B adt
types
.BR Attr ,
.B Tuple
and
.B Record
are direct analogues of the constructs defined above.
.P
.TP
.BI init( path )
.B Init
initialises the
.B Cfg
module, causing it to open and parse the configuration file
given by the
.I path
argument.
If an error is encountered in processing the file then
an error string is returned.
If there are no errors
.B init
returns
.BR nil .
.TP
.BI lookup( name )
.B Lookup
returns
the set of
.BR Record s
whose
.I key
matches the
.I name
argument.
The return value is a list of
.RI ( "primary record value" , " record" )
pairs.
.TP
.B getkeys()
.B 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
.BR getkeys() .
.TP
.IB record .lookup( name )
Returns the first tuple in
.I record
whose key matches
.IR name .
The return value is
.RI ( "primary tuple value" , " tuple" ).
If no matching tuple is found then the value
.B (nil, nil)
is returned.
Note that more than one tuple of the record could have a
.I key
that matches
.IR name .
Only the first matching tuple is returned.
If an application makes use of
multiple tuples with the same
.I key
then the
.IB record .tuple
list will have to be handled explicitly by the application.
.TP
.IB tuple .lookup( name )
Returns the first attribute in
.I tuple
whose name matches
.IR name .
The return value is the value of the attribute or
.B nil
if no matching attribute was found.
.SH SOURCE
.B /appl/lib/cfg.b