From Free Pascal wiki

Deutsch (de) English (en) español (es) français (fr) Bahasa Indonesia (id)

The RegExpr package includes a number of regular expressions implementations

Regexpr by Sorokin

This is the most complete implementation, available in packages/regexpr/src/regexpr.pas

Read the wikipedia page about regular expressions to get introduced to the subject: POSIX Basic Regular Expressions

This package implements a subset of Perl's regular expressions and the syntax provided by the package is documented here:

Change case on replaces

You can change case of found fragments, use modifiers in replace-with field (case change works after position of modifier):

  • \l - First char to lower
  • \L - All chars to lower
  • \u - First char to upper
  • \U - All chars to upper

E.g. if found a word, use replace-with field "\L$0" to change word to lowercase (here $0 is group 0, found text).

In addition \n will be replaced with the LineEnd character (or character sequence).

Simple usage example

Using Sorokin RegExpr to check if an expression is present in a string is very easy, just create an instance of TRegExpr, then place your regular expression in the property TRegExpr.Expression and use the method Exec to verify if there are any matches for this regular expression. Exec will return true if the expression matches the string passed to it.

  RegexObj: TRegExpr;
  RegexObj := TRegExpr.Create;
  RegexObj.Expression := '.*login.*';
  if RegexObj.Exec('Please try to login here') then WriteLn('The login was found!');

Subexpression match:

program Project1;


  re: TRegExpr;
  re := TRegExpr.Create('hello (.*?)!');
  if re.Exec('hello world! hello pascal!') then
    while re.ExecNext do



Regexpr by Joost

Regexpr by Joost (units oldregexpr.pp and regex.pp) is a very basic regex (Regular Expression) unit, it handles most regular expressions as GNU regexpr. The use of regex is to search patterns inside a string.

The current unit is far from complete, and still misses very simple syntax support of POSIX or more complex syntax such as Perl regex, Java Regex, Ruby Regex etc...

The unit contains 4 functions for now:

  • GenerateRegExprEngine – This function compiles the regex pattern.
  • RegExprPos – Finds the pattern inside a given string.
  • DestroyRegExprEngine – Free the compilation of the pattern
  • RegExprEscapeStr – Escape reserve syntax of regular expression language so it will be understood as string instead of regex syntax.

There is also one test:

  • The testreg1 test program demonstrates the supported regular expressions.

Regexpr by Florian

This is the oldest implementation. It is present in packages/regexpr/src/old and is not currently compiled by the makefiles, so it is not available precompiled by default in released FPC/Lazarus versions.

See Also

Go to back Packages List