Using INI Files

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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, create an ini file with the name "DB.ini" and the contents below, and save it in the same folder as the executable program.

[DB-INFO]
Author=Adam
Pass=secret
MaxAttempts=5
DBFile=C:\Money.dat

The code to read this ini file:

Program IniReadExample;
 
{$mode objfpc}{$H+}
 
uses
  classes, sysutils, IniFiles;
 
const
  C_DB_SECTION = 'DB-INFO';
 
var
  INI: TINIFile;
  Author, Pass, DBFile: String;
  MaxAttempts: integer;
  PassEnter: String;
  TryCount: integer;
begin
  // Create the object, specifying the the ini file that contains the settings
  INI := TINIFile.Create('DB.ini');
 
  // Put reading the INI file inside a try/finally block to prevent memory leaks
  try
    // Demonstrates reading values from the INI file.
    Author      := INI.ReadString(C_DB_SECTION,'Author','');
    Pass        := INI.ReadString(C_DB_SECTION,'Pass','');
    DBFile      := INI.ReadString(C_DB_SECTION,'DBFile','');
    MaxAttempts := INI.ReadInteger(C_DB_SECTION,'MaxAttempts',1);
 
    // Do something with the values read; e.g. verify the password
    if Pass <> '' then
    begin
      // Ask for the password, max attempts = MaxAttempts
      TryCount := MaxAttempts;
      repeat
        write('Please enter password; ', TryCount, ' attempt(s) left: ');
        readln(PassEnter);
        dec(TryCount);
        if (PassEnter <> Pass) and (TryCount > 0) then
          writeln('Wrong Password, please try again');
      until(PassEnter = Pass) or (TryCount = 0);
 
      // Correct password given?
      if PassEnter = Pass then
        writeln('Correct Password.')
      else
        writeln('Invalid password, but maxiumm number of password attempts reached.');
    end;
 
    writeln('Author               : ', Author);
    writeln('File                 : ', DBFile);
    writeln('Password             : ', Pass);
    writeln('Max password attempts: ', MaxAttempts);
    writeln;
    write('Press Enter to close...');
    Readln;
 
  finally
    // After the ini file was used it must be freed to prevent memory leaks.
    INI.Free;
  end;
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