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This page describes the Masks unit as per Lazarus version 2.3



The masks unit provides classes and functions for pattern matching using wildcards, sets/ranges and/or literal characters.

Controlling how the mask is interpreted


TMaskOpcodes is defined as set of TMaskOpcode.
The TMaskOpcode enumeration type consist of:

Name Interpretation
mocAnyChar Treat ? as a wildcard to match exactly one char
mocAnyCharOrNone Treat [?] to match any char or the absence of a char
mocAnyText Treat * as a wildcard to mach zero or any mumber of chars
mocRange treat [a-c] to match either 'a', 'b' or 'c'. '-' is treated as a range indicator.

To have a literal '-' in a range definition, you must escape it with EscapeChar (defaults to '\'): [+-\-] matches '+', ',', or '-'.

mocSet Treat [a-c] to match either 'a', '-' or 'c'
mocNegateGroup Treat [!a-c] to not match 'a', 'b', or 'c', but match any other char. Requires mocRange and/or mocSet
mocEscapeChar Treat EscapeChar (defaults to '\') to take the next char as a literal, so '\*' is treated as a literal '*'.

Predefined MaskOpcodes

The masks unit has some predefined MaskOpcodes constants.

Name Interpretation
AllMaskOpCodes Self explanatory.
MaskOpCodesDisableRange Do not interpret [ as the start of a range or set.
MaskOpCodesNoEscape Interpret [?] as a set with a literal question mark instead of 0..1 chars wildcard. Disable escaping.
DefaultMaskOpCodes Equals to MaskOpCodesNoEscape.

If no TMaskOpcodes parameter is supplied to one of the Matches methods or functions, DefaultMaskOpCodes is assumed.

Specific Windows Quirks

Windows mask works in a different mode than regular masks, it has many quirks and corner cases inherited from CP/M, then adapted to DOS (8.3) file names and adapted again for long file names.

TWindowsQuirks is defined as set of TWindowsQuirks.
The TWindowsQuirk enumeration type consists of:

Name Example mask Interpretation
wqAnyExtension Anything*.* The filename is not required to have an extension
wqFilenameEnd Anything??.abc The '?' matches 1 or 0 chars (except '.')
If you enable this quirk you must enable mocAnyCharorNone in the MaskOpCodes!
wqExtension3More Matches but also* (so '*.pas' also matches with 'file.pas.bak')
wqEmptyIsAny Empty string matches anything, so acts like '*'
wqAllByExtension .abc Is treated as *.abc
wqNoExtension Anything*. Matches Anything* without extension

TWindowsQuirks can only be used in the Windows specfic classses and functions.

Predefined TWindowsQuirks

The masks unit has some predefined WindowsQuirks constants.

Name Interpretation
AllWindowsQuirks Self explanatory.
DefaultWindowsQuirks Do not support wqExtension3More and wqAllByExtension

If no TWindowsQuirks parameter is supplied to one of the Windows specific Matches methods or functions, DefaultWindowsQuirks is assumed.

TMask classes

All pattern matching is done by the TMask classes.
The convenience functions like MatchesMask() internally use an instance of a TMask class.
Not all of the properties of the TMask classes are exposed in these convenience functions, so when you need more control over how the mask is interpreted, you should use a TMask class directly.
This also makes sense if you do multiple calls to a matching routine, this avoids repetetive creating of a TMask class instance.


Does pattern matching unix style (or should one say "non-Windows" style).
The mask '*.*' requires that there must be at least one period ('.') in the filename to match.

The following properties of TMask (and all other TMask classes) are not exposed in the aforementioned convenient functions:

Name Type Meaning
AutoReverseRange Boolean When True, it interprets the range [z-a] as [a-z], otherwise as an empty range.
Requires mocRange enabled.
EscapeChar Char The char used to escape characters that would otherwise have special meaning. E.g. '\*' will be interpreted as a literal '*'.
Requires mocEscapeChar.

To maintain backwards compatibility the TMask class provides the method MatchesWindowsMask(), but this hase been deprecated in favour of the direct use of the Matches method of TWindowsMask. This method will be removed in a future release.


Does pattern matching in Windows style.
So (by default) the mask '*.*' wil match any string of any (including zero) length, with or withoud a period it.
If you set it's property Quirks to [] (empty set), it will behave just like TMask.

TMaskList and TWindowsMaskList

These classes support pattarn matching against a list of patterns separated by a Separator (which defaults to ';').
Typically it will be used to match e.g. a list of filename extensions: '*.pas;*.pp;*.inc'.

Like TMask, the TMaskList class provides the method MatchesWindowsMask() for backwards compatibility. It's fate will be the same...

Code examples