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The parsecfg module implements a high performance configuration file parser. The configuration file's syntax is similar to the Windows .ini format, but much more powerful, as it is not a line based parser. String literals, raw string literals and triple quoted string literals are supported as in the Nim programming language.

Example of how a configuration file may look like:

# This is a comment.
; this too.

[Common]
cc=gcc     # '=' and ':' are the same
--foo="bar"   # '--cc' and 'cc' are the same, 'bar' and '"bar"' are the same (except for '#')
macrosym: "#"  # Note that '#' is interpreted as a comment without the quotation
--verbose

[Windows]
isConsoleApplication=False ; another comment

[Posix]
isConsoleApplication=True

key1: "in this string backslash escapes are interpreted\n"
key2: r"in this string not"
key3: """triple quotes strings
are also supported. They may span
multiple lines."""

--"long option with spaces": r"c:\myfiles\test.txt" 

Here is an example of how to use the configuration file parser:

Example: cmd: -r:off

import std/parsecfg
import std/[strutils, streams]

let configFile = "example.ini"
var f = newFileStream(configFile, fmRead)
assert f != nil, "cannot open " & configFile
var p: CfgParser
open(p, f, configFile)
while true:
  var e = next(p)
  case e.kind
  of cfgEof: break
  of cfgSectionStart:   ## a `[section]` has been parsed
    echo "new section: " & e.section
  of cfgKeyValuePair:
    echo "key-value-pair: " & e.key & ": " & e.value
  of cfgOption:
    echo "command: " & e.key & ": " & e.value
  of cfgError:
    echo e.msg
close(p)

Configuration file example

charset = "utf-8"
[Package]
name = "hello"
--threads:on
[Author]
name = "nim-lang"
website = "nim-lang.org"

Creating a configuration file

Example:

import std/parsecfg
var dict = newConfig()
dict.setSectionKey("","charset", "utf-8")
dict.setSectionKey("Package", "name", "hello")
dict.setSectionKey("Package", "--threads", "on")
dict.setSectionKey("Author", "name", "nim-lang")
dict.setSectionKey("Author", "website", "nim-lang.org")
assert $dict == """
charset=utf-8
[Package]
name=hello
--threads:on
[Author]
name=nim-lang
website=nim-lang.org
"""

Reading a configuration file

Example: cmd: -r:off

import std/parsecfg
let dict = loadConfig("config.ini")
let charset = dict.getSectionValue("","charset")
let threads = dict.getSectionValue("Package","--threads")
let pname = dict.getSectionValue("Package","name")
let name = dict.getSectionValue("Author","name")
let website = dict.getSectionValue("Author","website")
echo pname & "\n" & name & "\n" & website

Modifying a configuration file

Example: cmd: -r:off

import std/parsecfg
var dict = loadConfig("config.ini")
dict.setSectionKey("Author", "name", "nim-lang")
dict.writeConfig("config.ini")

Deleting a section key in a configuration file

Example: cmd: -r:off

import std/parsecfg
var dict = loadConfig("config.ini")
dict.delSectionKey("Author", "website")
dict.writeConfig("config.ini")

Supported INI File structure

Example:

import std/parsecfg
import std/streams

var dict = loadConfig(newStringStream("""[Simple Values]
    key=value
    spaces in keys=allowed
    spaces in values=allowed as well
    spaces around the delimiter = obviously
    you can also use : to delimit keys from values
    [All Values Are Strings]
    values like this: 19990429
    or this: 3.14159265359
    are they treated as numbers : no
    integers floats and booleans are held as: strings
    can use the API to get converted values directly: true
    [No Values]
    key_without_value
    # empty string value is not allowed =
    [ Seletion A   ]
    space around section name will be ignored
    [You can use comments]
    # like this
    ; or this
    # By default only in an empty line.
    # Inline comments can be harmful because they prevent users
    # from using the delimiting characters as parts of values.
    # That being said, this can be customized.
        [Sections Can Be Indented]
            can_values_be_as_well = True
            does_that_mean_anything_special = False
            purpose = formatting for readability
            # Did I mention we can indent comments, too?
    """)
)

let section1 = "Simple Values"
assert dict.getSectionValue(section1, "key") == "value"
assert dict.getSectionValue(section1, "spaces in keys") == "allowed"
assert dict.getSectionValue(section1, "spaces in values") == "allowed as well"
assert dict.getSectionValue(section1, "spaces around the delimiter") == "obviously"
assert dict.getSectionValue(section1, "you can also use") == "to delimit keys from values"

let section2 = "All Values Are Strings"
assert dict.getSectionValue(section2, "values like this") == "19990429"
assert dict.getSectionValue(section2, "or this") == "3.14159265359"
assert dict.getSectionValue(section2, "are they treated as numbers") == "no"
assert dict.getSectionValue(section2, "integers floats and booleans are held as") == "strings"
assert dict.getSectionValue(section2, "can use the API to get converted values directly") == "true"

let section3 = "Seletion A"
assert dict.getSectionValue(section3, 
  "space around section name will be ignored", "not an empty value") == ""

let section4 = "Sections Can Be Indented"
assert dict.getSectionValue(section4, "can_values_be_as_well") == "True"
assert dict.getSectionValue(section4, "does_that_mean_anything_special") == "False"
assert dict.getSectionValue(section4, "purpose") == "formatting for readability"