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// This package implements a parser for configuration files.
// This allows easy reading and writing of structured configuration files.
// Given the configuration file:
// [default]
// host =
// port = 443
// php = on
// [service-1]
// host =
// allow-writing = false
// To read this configuration file, do:
// c, err := conf.ReadConfigFile("server.conf")
// c.GetString("default", "host") // returns
// c.GetInt("", "port") // returns 443 (assumes "default")
// c.GetBool("", "php") // returns true
// c.GetString("service-1", "host") // returns
// c.GetBool("service-1","allow-writing") // returns false
// c.GetInt("service-1", "port") // returns 0 and a GetError
// Note that all section and option names are case insensitive. All values are case
// sensitive.
// Goconfig's string substitution syntax has not been removed. However, it may be
// taken out or modified in the future.
package conf
import (
// ConfigFile is the representation of configuration settings.
// The public interface is entirely through methods.
type ConfigFile struct {
data map[string]map[string]string // Maps sections to options to values.
const (
// Get Errors
SectionNotFound = iota
// Read Errors
// Get and Read Errors
var (
DefaultSection = "default" // Default section name (must be lower-case).
DepthValues = 200 // Maximum allowed depth when recursively substituing variable names.
// Strings accepted as bool.
BoolStrings = map[string]bool{
"t": true,
"true": true,
"y": true,
"yes": true,
"on": true,
"1": true,
"f": false,
"false": false,
"n": false,
"no": false,
"off": false,
"0": false,
varRegExp = regexp.MustCompile(`%\(([a-zA-Z0-9_.\-]+)\)s`)
// AddSection adds a new section to the configuration.
// It returns true if the new section was inserted, and false if the section already existed.
func (c *ConfigFile) AddSection(section string) bool {
section = strings.ToLower(section)
if _, ok :=[section]; ok {
return false
}[section] = make(map[string]string)
return true
// RemoveSection removes a section from the configuration.
// It returns true if the section was removed, and false if section did not exist.
func (c *ConfigFile) RemoveSection(section string) bool {
section = strings.ToLower(section)
switch _, ok :=[section]; {
case !ok:
return false
case section == DefaultSection:
return false // default section cannot be removed
for o, _ := range[section] {
delete([section], o)
delete(, section)
return true
// AddOption adds a new option and value to the configuration.
// It returns true if the option and value were inserted, and false if the value was overwritten.
// If the section does not exist in advance, it is created.
func (c *ConfigFile) AddOption(section string, option string, value string) bool {
c.AddSection(section) // make sure section exists
section = strings.ToLower(section)
option = strings.ToLower(option)
_, ok :=[section][option][section][option] = value
return !ok
// RemoveOption removes a option and value from the configuration.
// It returns true if the option and value were removed, and false otherwise,
// including if the section did not exist.
func (c *ConfigFile) RemoveOption(section string, option string) bool {
section = strings.ToLower(section)
option = strings.ToLower(option)
if _, ok :=[section]; !ok {
return false
_, ok :=[section][option]
delete([section], option)
return ok
// NewConfigFile creates an empty configuration representation.
// This representation can be filled with AddSection and AddOption and then
// saved to a file using WriteConfigFile.
func NewConfigFile() *ConfigFile {
c := new(ConfigFile) = make(map[string]map[string]string)
c.AddSection(DefaultSection) // default section always exists
return c
type GetError struct {
Reason int
ValueType string
Value string
Section string
Option string
func (err GetError) Error() string {
switch err.Reason {
case SectionNotFound:
return fmt.Sprintf("section '%s' not found", string(err.Section))
case OptionNotFound:
return fmt.Sprintf("option '%s' not found in section '%s'", string(err.Option), string(err.Section))
case CouldNotParse:
return fmt.Sprintf("could not parse %s value '%s'", string(err.ValueType), string(err.Value))
case MaxDepthReached:
return fmt.Sprintf("possible cycle while unfolding variables: max depth of %d reached", int(DepthValues))
return "invalid get error"
type ReadError struct {
Reason int
Line string
func (err ReadError) Error() string {
switch err.Reason {
case BlankSection:
return "empty section name not allowed"
case CouldNotParse:
return fmt.Sprintf("could not parse line: %s", string(err.Line))
return "invalid read error"