4 This document describes run-time configuration of libucw-based
5 programs using config files. For compile-time configuration,
11 Configuration items of all modules are organized into sections.
12 The sections form a tree structure with top-level sections corresponding
15 Each configuration item belongs to one of the following classes:
17 1. single value or a fixed-length array of values
18 2. variable-length array of values
19 3. subsection with several nested attributes
20 4. list of nodes, each being an instance of a subsection
21 5. bitmap of small integers (0..31) or fixed list of strings
22 6. exceptions (items with irregular syntax; however, they always
23 appear as a sequence of strings, only the semantics differ)
25 Both fixed- and variable-length arrays consist of items of the same
26 type. The basic types supported by the configuration mechanism are:
30 3. floating point number
33 6. choice (one of a fixed list of strings)
35 Program modules can define their own special types (such as network
36 masks or attribute names) and decide how are they parsed.
38 Format of configuration files
39 -----------------------------
41 Configuration files are text files that usually set one attribute per
42 line, though it is possible to split one assignment into multiple lines
43 and/or assign several attributes in one line. The basic format of an
46 name value1 value2 ... valueN
50 name=value1 value2 ... valueN
52 The end of line means also end of a command unless it is preceded by a
53 backslash. On the other hand, a semicolon terminates the command and
54 another command can start after the semicolon. A hash starts a comment
55 that lasts until the end of the line. A value can be enclosed in
56 apostrophes or quotation marks and then it can contain spaces and/or
57 control characters, otherwise the first space or control character
58 denotes the end of the value. Values enclosed in quotation marks are
59 interpreted as C-strings. For example, the following are valid
62 Database "main db\x2b"; Directory='index/'; Weights 100 20 30 \
63 40 50 80 # a comment that is ignored
65 Numerical values can be succeeded by a unit. The following units are
69 h=3600 m=1000000 M=1048576
70 %=0.01 g=1000000000 G=1073741824
72 Attributes of a section or a list node can be set in two ways. First,
73 you can write the name of the section or list, open a bracket, and then
74 set the attributes inside the section. For example,
79 ListNode { #creates a list and adds its first node
83 ListNode { Attr3=value5; Attr4=value6 }
84 #appends a new node; this is still the same syntax
87 The second possibility is using a shorter syntax when all attributes of a
88 section are set on one line in a fixed order. The above example could
94 ListNode value3 value4
95 ListNode value5 value6
98 Of course, you cannot use the latter syntax when the attributes allow
99 variable numbers of parameters. The parser of the configuration files
100 checks this possibility.
102 If you want to set a single attribute in some section, you can also
103 refer to the attribute as Section.Attribute.
105 Lists support several operations besides adding a new node. You just
106 have to write a colon immediately after the attribute name, followed by
107 the name of the operation. The following operations are supported:
109 List:clear # removes all nodes
110 List:append { attr1=value1; ... } # adds a new node at the end
111 List:prepend { attr1=value1; ... } # adds a new node at the beginning
112 List:remove { attr1=search1 } # find a node and delete it
113 List:edit { attr1=search1 } { attr1=value1; ... }
114 # find a node and edit it
115 List:after { attr1=search1 } { ... } # insert a node after a found node
116 List:before { attr1=search1 } { ... } # insert a node before a found node
117 List:copy { attr1=search1 } { ... } # duplicate a node and edit the copy
119 You can specify several attributes in the search condition and the nodes
120 are tested for equality in all these attributes. In the editing
121 commands, you can either open a second block with overridden attributes,
122 or specify the new values using the shorter one-line syntax.
124 The commands :clear, :append, and :prepend are also supported by var-length
125 arrays. The command :clear can also be used on string values. The following
126 operations can be used on bitmaps: :set, :remove, :clear, and :all.
128 Including other files
129 ---------------------
131 To include another file, use the command
135 (Beware that this command has to be the last one on the line.)
137 Command-line parameters
138 -----------------------
140 The default configuration file (cf_def_file possibly overriden
141 by environment variable cf_env_file) is read before the program is started.
142 You can use a -C option to override the name of the configuration file.
143 If you use this parameter several times, then all those files are loaded
144 consecutively. A parameter -S can be used to execute a configuration
145 command directly (after loading the default or specified configuration
148 bin/program -Ccf/my-config -S'module.trace=2;module.logfile:clear' ...
150 If the program is compiled with debugging information, then one more
151 parameter `--dumpconfig` is supported. It prints all parsed configuration
154 All these switches must be used before any other parameters of the
160 During compilation, all configuration files are pre-processed by a simple
161 C-like preprocessor, which supports `#ifdef`, `#ifndef`, `#if`,
162 `#elsif`, `#else` and `#endif` directives referring to compile-time
163 configuration variables. `#if` and `#elsif` can contain any Perl expression
164 where each `CONFIG_xyz` configuration variable is substituted to 0 or 1
165 depending on its value.
167 The preprocessor also substitutes `@VARIABLE@` by the value of the variable,
168 which must be defined.
173 Trying to access an unknown attribute causes an error, but unrecognized
174 top-level sections are ignored. The reason is that a common config file
175 is used for a lot of programs which recognize only their own sections.
177 Names of sections, attributes and choices are case-insensitive. Units are