Using INI Files

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Revision as of 23:56, 1 January 2016 by Eny (talk | contribs) (Fix errors in ini-file (make FCL compliant))
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INI Files

Basic Information

INI files are text files that store key/value pairs that are grouped in sections.

INI files can be used to save user settings easily. With the IniFiles unit and the TINIFile class you can easily work with them. The IniFiles unit is part of the FCL.

Currently only INI files compliant with the more restrictive Windows ini-file format are supported. I.e. using sections is mandatory and only the semicolon can be used for comments. For more general information about ini-files read this.

INI Files

INI Files use brackets to create and mark Sections, which contain keys and key values. A Key and its corresponding Value are separated with an equals sign (Key=Value).

Section names are put inside square brackets ([Section]).

Comments are permitted and are marked with a semicolon (;) at the beginning of a line.

An example ini file:

; Comment. Beginning of INI file

; empty lines are ignored

[General]
; This starts a General section
Compiler=FreePascal
; Key Compiler and value FreePascal

Ini file reading example

The console application below shows how to read ini files. To test it one should create the following ini file with the name "C:\DB.ini". Edit it to so it contains a section called INIDB and the following keys and values:

[INIDB]
; Save as C:\DB.ini
Author=Adam
Pass=
DBFile=C:\Money.dat

Now let's move on the the code..

Program IniSample;

{$mode objfpc}{$H+}

Uses
  Classes,SysUtils,INIFiles;

Var
 INI:TINIFile;
 Author,Pass,DBFile:String;
 PassEnter:String;

begin
  // Create the object, specifying the place where it can find the ini file:
  INI := TINIFile.Create('C:\DB.ini');
  // Demonstrates reading strings from the INI file.
  // You can also read booleans etc.
  Author := INI.ReadString('INIDB','Author','');
  Pass := INI.ReadString('INIDB','Pass','');
  DBFile := INI.ReadString('INIDB','DBFile','');
  if Pass <> '' then
  begin
    Writeln('Password Required');
    Repeat
      Readln(PassEnter);
      if not (PassEnter = Pass) then Writeln('Wrong Password');
    until(PassEnter = Pass);
    Writeln('Correct Password');
  end;
  Writeln('Author : '+Author);
  Writeln('File : '+DBFile);
  Writeln('Password : '+Pass);
  Readln;
  // After we used ini file, we must call the Free method of object
  // ... although this really should be wrapped in a try..finally block
  // so that the object will be freed regardless of any errors above.
  Ini.Free; 
end.

Objects to know

In the TINIFile class there are many different properties, procedures and functions that can be used.

CaseSensitive - This property allows you to say if the keys and sections are case sensitive or not. By default they aren't.

ReadString - Has 3 constant statements. The first one is the section to search in. The second one is the key to look for. The third one is a default string in case the key and/or section searched for is not found.

WriteString - has three constant statements, too. The first is the section. The second is the key and the last is the value that you want to write. If the key and section exist already, the key will be overwritten with the new value..

ReadSections - Will allow you to to take the sections from the INI file and put them in a TStrings class (or TStringList with the AS operator).

DeleteKey - Remove an existing key from a specific section.

EraseSection - Remove a section and all its data.

There are more procedures and functions but this is enough to get you started.

Reference Documentation

Here: Free Pascal documentation on INI files

See also