Get that keyvalue from INI!

bash-ini-file

From an INI-format (v1.4) file, be able to extract any keyvalue by its section/keyword ... in bash.

You got an INI file, I've got the bash script in which to get your settings from with.

Works with:

• systemd configuration file
• Python configuration file
• NetworkManager configuration file
• ifup/down configuration file
• PHP configuration file
• Windows .INI

Treats a no-section (any keyword=keyvalue before a [section]) as a '[Default]'; reads both no-section and [Default] together as [Default].

Also correctly finds the last keyvalue of the desired section/keyword before extracting its keyvalue, despite its multiply-defined/multiple-reused interspersed/alternating section blocks.

Details

File format: .INI Supported version: 1.4 (2009)

Features

Currently supported features are:

• loads all settings into a multi-line bash string (no need for variable array)
• Treats no-section as '[Default]'; reads both sections together as Default.
• Check the section name and keyword name for valid character set.
• Nested quotes also works alongside with inline comment (except for '//' inline comment support)
• Supports and ignores inline comment using semicolon ';', hashmark '#'; But the double-slash '//' regex has been properly defined but not yet integrated as bash yet. See Issue 1.
• Some 30,000 keyvalue lookups per second, no it is more like 20/second; well, like performance really matters here anyway.

HOW I DID THIS

The secret sauce is to convert the entire INI file into a parsable syntax format just with this one awk programming:

/^\[.*\]$/{obj=$0}/=/{print obj $0}'

so a bash line was born:

ini_buffer="$(print "%s" "$raw_buffer" | awk '/^\[.*\]$/{obj=$0}/=/{print obj $0}')"

Standardized INI Table Format

Next is to standardize the INI to a common syntax format:

[section]keyword=keyvalue

An example INI file might look like this:

loneSetting=0

[Network]
DNS=1.1.1.1

[Default]
FirstDefaultKeyword=1

get turned into this:

[Default]loneSetting=0
[Network]DNS=1.1.1.1
[Default]FirstDefaultKeyword=1

Note: Notice that we treated the 'no-section' as [Default]?

Parsable Galore!

With the usage of a common [section]keyword=keyvalue format, it now becomes easily possible to work with INI line-records in a faster manner using sed, awk and tail or even grep.

APIs, APIs, Lots of API; well, just a few.

Simply source the lone script file: bash-ini-parser.sh and start calling APIs such as:

API	$?	STDOUT	Description
ini_read_file	-	multi-line	Converts an INI-format file content into a variable containing an INI table
ini_section_name_normalize	0/1	string	Normalize the section name into an acceptable form of INI-compliant name.
ini_section_list	0/1	string	Outputs a list of section name(s) found in the INI table
ini_section_extract	-	multi-line	Extract one or more INI table records having this matching 'section' name
ini_keyword_name_normalize	0/1	string	Normalize the keyword name into an acceptable form of INI-compliant name.
ini_keyword_valid	0/1	-	Assert that the keyword is valid for use in a INI file.
ini_keyword_list	0/1	string	Outputs a list of keyword name(s) found by a specified section in INI table
ini_keyword_extract	-	multi-line	Extracts one or more INI records having matching keyword from an INI table
ini_keyvalue_get	-	multi-line	Get the key value based on given section name and keyword name (most useful with systemd, NetworkManager.
ini_keyvalue_get_last	-	string	Get the LAST key value encountered given a section name and a keyword name. (most useful if only interested by matched keyword for the last keyword=keyvalue to obtain its overridden keyvalue.

Demo

A nice bash script can be either my example-usage.sh script or below:

source bash-ini-parser.sh
read -rd '' raw_data < <(cat "/etc/systemd/system/display-manager.service")
read -rd '' ini_service_section < <(ini_file_read "$raw_data")
ini_keyvalue_get "$ini_service_section" "Service" "ExecStart"
# outputs the keyvalue

Or with example-usage.sh, this script will try to read systemd config file and determine which Display Manager that you are using:

$ bash example-usage.sh 
File    : /etc/systemd/system/display-manager.service
Keyword : ExecStart
Keyvalue: /usr/bin/sddm  # <--- your section/keyword/keyvalue answer

Came from all that below:
"[Unit]Description=Simple Desktop Display Manager
[Unit]Documentation=man:sddm(1) man:sddm.conf(5)
[Unit]Conflicts=getty@tty1.service getty@tty7.service
[Unit]After=getty@tty1.service getty@tty7.service
[Unit]After=systemd-user-sessions.service systemd-logind.service
[Unit]After=haveged.service
[Service]ExecStart=/usr/bin/sddm
[Service]Restart=always
[Service]RestartSec=1s
[Service]EnvironmentFile=-/etc/default/locale
[Install]Alias=display-manager.service"

Done.

Unit Test

The accompanied tests subdirectory performs the comprehensive unit testing, in case you have decided to tweaked it to your normative scenario; hopefully, this will find any errors of yours.

To exercise a specific unit test, your modified bash-ini-parser.sh must reside above the tests directory as all the unit tests will perform and find your modified script 'above':

#!/bin/bash
# Title: my script file

source ../bash-ini-parser.sh

...

Supreme Unit Testing

To start the global unit test, execute:

cd tests
./test-all.sh

and the output is long, very long, very very long.

Selective Unit Test

To perform a specific unit test, for example, ini_keyvalue_get(), execute:

$ bash test-ini-keyvalue-get.sh 
assert_keyvalue_get([Default]DNS=): pass # same keyword, 'Default' section
assert_keyvalue_get([Resolve]DNS=): pass # same keyword, 'Resolve' section
assert_keyvalue_get([Default]DNS=): pass # empty ini_file
assert_keyvalue_get([Default]DNS=): pass # new line
assert_keyvalue_get([Default]DNS=): pass # hash mark no-comment
assert_keyvalue_get([Default]DNS=): pass # semicolon no-comment
assert_keyvalue_get([Default]DNS=): pass # slash-slash no-comment
assert_keyvalue_get([Default]DNS=): pass # hash mark comment
assert_keyvalue_get([Default]DNS=): pass # semicolon comment
assert_keyvalue_get([Default]DNS=): pass # slash-slash comment
assert_keyvalue_get([NoSuchSection]DNS=): pass # same keyword, 'NoSuchSection' section
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([Resolve]DNS=): pass # unused keyword, 'Resolve' section
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([Resolve]DNS=): pass # unused keyword, 'Resolve' section
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([Default]FallbackDNS=): pass # standard
assert_keyvalue_get([Resolve]DNS=): pass # incomplete but matching keyword, 'Resolve' section
assert_keyvalue_get([Resolve]DNS_Server1=): pass # incomplete but matching keyword, 'Resolve' section, NULL answer
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([Gateway]Hidden_DNS_Master=): pass # unique section, underscored keyword
assert_keyvalue_get([NoSuchSection]DNS=): pass # unique section, unused keyword, noSuchSection
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([Resolve]DNS=): pass # keyword 2 of 2, 'Resolve' section
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([Default]FallbackDNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server1=): pass # standard
assert_keyvalue_get([DifferentSection]DNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server2=): pass # standard
assert_keyvalue_get([DifferentSection2]DNS_2=): pass # standard
assert_keyvalue_get([Resolve]DNS=): pass # standard
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([Default]FallbackDNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server1=): pass # standard
assert_keyvalue_get([DifferentSection]DNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server2=): pass # standard
assert_keyvalue_get([DifferentSection2]DNS_2=): pass # standard
assert_keyvalue_get([Resolve]DNS=): pass # standard
assert_keyvalue_get([Gateway]Hidden_DNS_Master=): pass # standard
assert_keyvalue_get([]=): pass # unused keyword
assert_keyvalue_get([]DNS=): pass # unused keyword, 'no-section default
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused keyword, noSuchSection
assert_keyvalue_get([Default]FallbackDNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server1=): pass # standard
assert_keyvalue_get([DifferentSection]DNS=): pass # standard
assert_keyvalue_get([Resolve]DNS_Server2=): pass # standard
assert_keyvalue_get([DifferentSection2]DNS_2=): pass # standard
assert_keyvalue_get([Resolve]DNS=): pass # standard
assert_keyvalue_get([Gateway]Hidden_DNS_Master=): pass # standard
assert_keyvalue_get([Gateway]Hidden_DNS_Master2=): pass # standard
assert_keyvalue_get([]=): pass # no section, no keyword
assert_keyvalue_get([]DNS=): pass # no-section, unused keyword
assert_keyvalue_get([NoSuchSection]DNS=): pass # unused section, unused keyword
assert_keyvalue_get([Default]FallbackDNS=): pass # # inside double-quote
assert_keyvalue_get([Resolve]DNS_Server1=): pass # ; inside double-quote
assert_keyvalue_get([DifferentSection]DNS=): pass # // inside double-quote
assert_keyvalue_get([Resolve]DNS_Server2=): pass # ; inside LHS double-quote
assert_keyvalue_get([DifferentSection2]DNS_2=): pass # // inside LHS double-quote
assert_keyvalue_get([Resolve]DNS=): pass # ; inside RHS double-quote
assert_keyvalue_get([Gateway]Hidden_DNS_Master=): pass # # inside RHS double-quote
assert_keyvalue_get([Gateway]Hidden_DNS_Master2=): pass # // inside RHS double-quote
assert_keyvalue_get([Default]FallbackDNS=): pass # # inside double-quote and outside
assert_keyvalue_get([Resolve]DNS_Server1=): pass # ; inside quote and outside
assert_keyvalue_get([Resolve]DNS_Server2=): pass # ; inside LHS double-quote and outside
assert_keyvalue_get([Resolve]DNS=): pass # ; inside RHS double-quote and outside
assert_keyvalue_get([Gateway]Hidden_DNS_Master2=): failed # // inside RHS double-quote and outside
  expected: '"78.78.78.78//"'
  actual  : '"78.78.78.78//"  // inline '/' '/' RHS double-quote'

Oh, please disregard the failed at the last line for I have filed Issue 1.