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< td align = "right" valign = "center" > < img src = "logo32.png" align = "right" width = "64" height = "32" border = "0" > < / td > < / tr > < / table > < h1 align = center > TQRegExp Class Reference< / h1 >
< p > The TQRegExp class provides pattern matching using regular expressions.
< a href = "#details" > More...< / a >
< p > All the functions in this class are < a href = "threads.html#reentrant" > reentrant< / a > when TQt is built with thread support.< / p >
< p > < tt > #include < < a href = "qregexp-h.html" > ntqregexp.h< / a > > < / tt >
< p > < a href = "qregexp-members.html" > List of all member functions.< / a >
< h2 > Public Members< / h2 >
< ul >
< li class = fn > enum < a href = "#CaretMode-enum" > < b > CaretMode< / b > < / a > { CaretAtZero, CaretAtOffset, CaretWontMatch }< / li >
< li class = fn > < a href = "#TQRegExp" > < b > TQRegExp< / b > < / a > ()< / li >
< li class = fn > < a href = "#TQRegExp-2" > < b > TQRegExp< / b > < / a > ( const TQString & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )< / li >
< li class = fn > < a href = "#TQRegExp-3" > < b > TQRegExp< / b > < / a > ( const TQRegExp & rx )< / li >
< li class = fn > < a href = "#~TQRegExp" > < b > ~TQRegExp< / b > < / a > ()< / li >
< li class = fn > TQRegExp & < a href = "#operator-eq" > < b > operator=< / b > < / a > ( const TQRegExp & rx )< / li >
< li class = fn > bool < a href = "#operator-eq-eq" > < b > operator==< / b > < / a > ( const TQRegExp & rx ) const< / li >
< li class = fn > bool < a href = "#operator!-eq" > < b > operator!=< / b > < / a > ( const TQRegExp & rx ) const< / li >
< li class = fn > bool < a href = "#isEmpty" > < b > isEmpty< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#isValid" > < b > isValid< / b > < / a > () const< / li >
< li class = fn > TQString < a href = "#pattern" > < b > pattern< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setPattern" > < b > setPattern< / b > < / a > ( const TQString & pattern )< / li >
< li class = fn > bool < a href = "#caseSensitive" > < b > caseSensitive< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setCaseSensitive" > < b > setCaseSensitive< / b > < / a > ( bool sensitive )< / li >
< li class = fn > bool < a href = "#wildcard" > < b > wildcard< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setWildcard" > < b > setWildcard< / b > < / a > ( bool wildcard )< / li >
< li class = fn > bool < a href = "#minimal" > < b > minimal< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setMinimal" > < b > setMinimal< / b > < / a > ( bool minimal )< / li >
< li class = fn > bool < a href = "#exactMatch" > < b > exactMatch< / b > < / a > ( const TQString & str ) const< / li >
< li class = fn > int match ( const TQString & str, int index = 0, int * len = 0, bool indexIsStart = TRUE ) const < em > (obsolete)< / em > < / li >
< li class = fn > int < a href = "#search" > < b > search< / b > < / a > ( const TQString & str, int offset = 0, CaretMode caretMode = CaretAtZero ) const< / li >
< li class = fn > int < a href = "#searchRev" > < b > searchRev< / b > < / a > ( const TQString & str, int offset = -1, CaretMode caretMode = CaretAtZero ) const< / li >
< li class = fn > int < a href = "#matchedLength" > < b > matchedLength< / b > < / a > () const< / li >
< li class = fn > int < a href = "#numCaptures" > < b > numCaptures< / b > < / a > () const< / li >
< li class = fn > TQStringList < a href = "#capturedTexts" > < b > capturedTexts< / b > < / a > ()< / li >
< li class = fn > TQString < a href = "#cap" > < b > cap< / b > < / a > ( int nth = 0 )< / li >
< li class = fn > int < a href = "#pos" > < b > pos< / b > < / a > ( int nth = 0 )< / li >
< li class = fn > TQString < a href = "#errorString" > < b > errorString< / b > < / a > ()< / li >
< / ul >
< h2 > Static Public Members< / h2 >
< ul >
< li class = fn > TQString < a href = "#escape" > < b > escape< / b > < / a > ( const TQString & str )< / li >
< / ul >
< hr > < a name = "details" > < / a > < h2 > Detailed Description< / h2 >
The TQRegExp class provides pattern matching using regular expressions.
< p >
<!-- index regular expression --> < a name = "regular-expression" > < / a >
< p > Regular expressions, or "regexps", provide a way to find patterns
within text. This is useful in many contexts, for example:
< p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#f0f0f0" > < td valign = "top" > Validation
< td valign = "top" > A regexp can be used to check whether a piece of text
meets some criteria, e.g. is an integer or contains no
whitespace.
< tr bgcolor = "#d0d0d0" > < td valign = "top" > Searching
< td valign = "top" > Regexps provide a much more powerful means of searching
text than simple string matching does. For example we can
create a regexp which says "find one of the words 'mail',
'letter' or 'correspondence' but not any of the words
'email', 'mailman' 'mailer', 'letterbox' etc."
< tr bgcolor = "#f0f0f0" > < td valign = "top" > Search and Replace
< td valign = "top" > A regexp can be used to replace a pattern with a piece of
text, for example replace all occurrences of '& ' with
'& amp;' except where the '& ' is already followed by 'amp;'.
< tr bgcolor = "#d0d0d0" > < td valign = "top" > String Splitting
< td valign = "top" > A regexp can be used to identify where a string should be
split into its component fields, e.g. splitting tab-delimited
strings.
< / table > < / center >
< p > We present a very brief introduction to regexps, a description of
TQt's regexp language, some code examples, and finally the function
documentation itself. TQRegExp is modeled on Perl's regexp
language, and also fully supports Unicode. TQRegExp can also be
used in the weaker 'wildcard' (globbing) mode which works in a
similar way to command shells. A good text on regexps is < em > Mastering Regular Expressions: Powerful Techniques for Perl and Other Tools< / em > by Jeffrey E. Friedl, ISBN 1565922573.
< p > Experienced regexp users may prefer to skip the introduction and
go directly to the relevant information.
< p > In case of multi-threaded programming, note that TQRegExp depends on
< a href = "ntqthreadstorage.html" > TQThreadStorage< / a > internally. For that reason, TQRegExp should only be
used with threads started with < a href = "ntqthread.html" > TQThread< / a > , i.e. not with threads
started with platform-specific APIs.
< p > <!-- toc -->
< ul >
< li > < a href = "#1" > Introduction
< / a >
< li > < a href = "#1-1" > Characters and Abbreviations for Sets of Characters
< / a >
< li > < a href = "#1-2" > Sets of Characters
< / a >
< li > < a href = "#1-3" > Quantifiers
< / a >
< li > < a href = "#1-4" > Capturing Text
< / a >
< li > < a href = "#1-5" > Assertions
< / a >
< li > < a href = "#1-6" > Wildcard Matching (globbing)
< / a >
< li > < a href = "#1-7" > Notes for Perl Users
< / a >
< li > < a href = "#1-8" > Code Examples
< / a >
< / ul >
<!-- endtoc -->
< p > < h3 > Introduction
< / h3 >
< a name = "1" > < / a > < p > Regexps are built up from expressions, quantifiers, and assertions.
The simplest form of expression is simply a character, e.g.
< b > x< / b > or < b > 5< / b > . An expression can also be a set of
characters. For example, < b > [ABCD]< / b > , will match an < b > A< / b > or
a < b > B< / b > or a < b > C< / b > or a < b > D< / b > . As a shorthand we could
write this as < b > [A-D]< / b > . If we want to match any of the
captital letters in the English alphabet we can write
< b > [A-Z]< / b > . A quantifier tells the regexp engine how many
occurrences of the expression we want, e.g. < b > x{1,1}< / b > means
match an < b > x< / b > which occurs at least once and at most once.
We'll look at assertions and more complex expressions later.
< p > Note that in general regexps cannot be used to check for balanced
brackets or tags. For example if you want to match an opening html
< tt > < b> < / tt > and its closing < tt > < /b> < / tt > you can only use a regexp if you
know that these tags are not nested; the html fragment, < tt > < b> bold < b> bolder< /b> < /b> < / tt > will not match as expected. If you know the
maximum level of nesting it is possible to create a regexp that
will match correctly, but for an unknown level of nesting, regexps
will fail.
< p > We'll start by writing a regexp to match integers in the range 0
to 99. We will require at least one digit so we will start with
< b > [0-9]{1,1}< / b > which means match a digit exactly once. This
regexp alone will match integers in the range 0 to 9. To match one
or two digits we can increase the maximum number of occurrences so
the regexp becomes < b > [0-9]{1,2}< / b > meaning match a digit at
least once and at most twice. However, this regexp as it stands
will not match correctly. This regexp will match one or two digits
< em > within< / em > a string. To ensure that we match against the whole
string we must use the anchor assertions. We need < b > ^< / b > (caret)
which when it is the first character in the regexp means that the
regexp must match from the beginning of the string. And we also
need < b > $< / b > (dollar) which when it is the last character in the
regexp means that the regexp must match until the end of the
string. So now our regexp is < b > ^[0-9]{1,2}$< / b > . Note that
assertions, such as < b > ^< / b > and < b > $< / b > , do not match any
characters.
< p > If you've seen regexps elsewhere they may have looked different from
the ones above. This is because some sets of characters and some
quantifiers are so common that they have special symbols to
represent them. < b > [0-9]< / b > can be replaced with the symbol
< b > \d< / b > . The quantifier to match exactly one occurrence,
< b > {1,1}< / b > , can be replaced with the expression itself. This means
that < b > x{1,1}< / b > is exactly the same as < b > x< / b > alone. So our 0
to 99 matcher could be written < b > ^\d{1,2}$< / b > . Another way of
writing it would be < b > ^\d\d{0,1}$< / b > , i.e. from the start of the
string match a digit followed by zero or one digits. In practice
most people would write it < b > ^\d\d?$< / b > . The < b > ?< / b > is a
shorthand for the quantifier < b > {0,1}< / b > , i.e. a minimum of no
occurrences a maximum of one occurrence. This is used to make an
expression optional. The regexp < b > ^\d\d?$< / b > means "from the
beginning of the string match one digit followed by zero or one
digits and then the end of the string".
< p > Our second example is matching the words 'mail', 'letter' or
'correspondence' but without matching 'email', 'mailman',
'mailer', 'letterbox' etc. We'll start by just matching 'mail'. In
full the regexp is, < b > m{1,1}a{1,1}i{1,1}l{1,1}< / b > , but since
each expression itself is automatically quantified by < b > {1,1}< / b >
we can simply write this as < b > mail< / b > ; an 'm' followed by an 'a'
followed by an 'i' followed by an 'l'. The symbol '|' (bar) is
used for < em > alternation< / em > , so our regexp now becomes
< b > mail|letter|correspondence< / b > which means match 'mail' < em > or< / em >
'letter' < em > or< / em > 'correspondence'. Whilst this regexp will find the
words we want it will also find words we don't want such as
'email'. We will start by putting our regexp in parentheses,
< b > (mail|letter|correspondence)< / b > . Parentheses have two effects,
firstly they group expressions together and secondly they identify
parts of the regexp that we wish to < a href = "#capturing-text" > capture< / a > . Our regexp still matches any of the three words but now
they are grouped together as a unit. This is useful for building
up more complex regexps. It is also useful because it allows us to
examine which of the words actually matched. We need to use
another assertion, this time < b > \b< / b > "word boundary":
< b > \b(mail|letter|correspondence)\b< / b > . This regexp means "match
a word boundary followed by the expression in parentheses followed
by another word boundary". The < b > \b< / b > assertion matches at a < em > position< / em > in the regexp not a < em > character< / em > in the regexp. A word
boundary is any non-word character such as a space a newline or
the beginning or end of the string.
< p > For our third example we want to replace ampersands with the HTML
entity '& amp;'. The regexp to match is simple: < b > & < / b > , i.e.
match one ampersand. Unfortunately this will mess up our text if
some of the ampersands have already been turned into HTML
entities. So what we really want to say is replace an ampersand
providing it is not followed by 'amp;'. For this we need the
negative lookahead assertion and our regexp becomes:
< b > & (?!amp;)< / b > . The negative lookahead assertion is introduced
with '(?!' and finishes at the ')'. It means that the text it
contains, 'amp;' in our example, must < em > not< / em > follow the expression
that preceeds it.
< p > Regexps provide a rich language that can be used in a variety of
ways. For example suppose we want to count all the occurrences of
'Eric' and 'Eirik' in a string. Two valid regexps to match these
are < b > \ b(Eric|Eirik)\ b< / b > and < b > \ bEi?ri[ck]\ b< / b > . We need
the word boundary '\b' so we don't get 'Ericsson' etc. The second
regexp actually matches more than we want, 'Eric', 'Erik', 'Eiric'
and 'Eirik'.
< p > We will implement some the examples above in the
< a href = "#code-examples" > code examples< / a > section.
< p > < a name = "characters-and-abbreviations-for-sets-of-characters" > < / a >
< h3 > Characters and Abbreviations for Sets of Characters
< / h3 >
< a name = "1-1" > < / a > < p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#a2c511" > < th valign = "top" > Element < th valign = "top" > Meaning
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > c< / b >
< td valign = "top" > Any character represents itself unless it has a special
regexp meaning. Thus < b > c< / b > matches the character < em > c< / em > .
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ c< / b >
< td valign = "top" > A character that follows a backslash matches the character
itself except where mentioned below. For example if you
wished to match a literal caret at the beginning of a string
you would write < b > \ ^< / b > .
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ a< / b >
< td valign = "top" > This matches the ASCII bell character (BEL, 0x07).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ f< / b >
< td valign = "top" > This matches the ASCII form feed character (FF, 0x0C).
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ n< / b >
< td valign = "top" > This matches the ASCII line feed character (LF, 0x0A, Unix newline).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ r< / b >
< td valign = "top" > This matches the ASCII carriage return character (CR, 0x0D).
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ t< / b >
< td valign = "top" > This matches the ASCII horizontal tab character (HT, 0x09).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ v< / b >
< td valign = "top" > This matches the ASCII vertical tab character (VT, 0x0B).
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ xhhhh< / b >
< td valign = "top" > This matches the Unicode character corresponding to the
hexadecimal number hhhh (between 0x0000 and 0xFFFF). \ 0ooo
(i.e., \zero ooo) matches the ASCII/Latin-1 character
corresponding to the octal number ooo (between 0 and 0377).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > . (dot)< / b >
< td valign = "top" > This matches any character (including newline).
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ d< / b >
< td valign = "top" > This matches a digit (< a href = "qchar.html#isDigit" > TQChar::isDigit< / a > ()).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ D< / b >
< td valign = "top" > This matches a non-digit.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ s< / b >
< td valign = "top" > This matches a whitespace (< a href = "qchar.html#isSpace" > TQChar::isSpace< / a > ()).
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ S< / b >
< td valign = "top" > This matches a non-whitespace.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ w< / b >
< td valign = "top" > This matches a word character (< a href = "qchar.html#isLetterOrNumber" > TQChar::isLetterOrNumber< / a > () or '_').
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ W< / b >
< td valign = "top" > This matches a non-word character.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ n< / b >
< td valign = "top" > The n-th < a href = "#capturing-text" > backreference< / a > ,
e.g. \ 1, \ 2, etc.
< / table > < / center >
< p > < em > Note that the C++ compiler transforms backslashes in strings so to include a < b > \ < / b > in a regexp you will need to enter it twice, i.e. < b > \ \ < / b > .< / em >
< p > < a name = "sets-of-characters" > < / a >
< h3 > Sets of Characters
< / h3 >
< a name = "1-2" > < / a > < p > Square brackets are used to match any character in the set of
characters contained within the square brackets. All the character
set abbreviations described above can be used within square
brackets. Apart from the character set abbreviations and the
following two exceptions no characters have special meanings in
square brackets.
< p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > ^< / b >
< td valign = "top" > The caret negates the character set if it occurs as the
first character, i.e. immediately after the opening square
bracket. For example, < b > [abc]< / b > matches 'a' or 'b' or 'c',
but < b > [^abc]< / b > matches anything < em > except< / em > 'a' or 'b' or
'c'.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > -< / b >
< td valign = "top" > The dash is used to indicate a range of characters, for
example < b > [W-Z]< / b > matches 'W' or 'X' or 'Y' or 'Z'.
< / table > < / center >
< p > Using the predefined character set abbreviations is more portable
than using character ranges across platforms and languages. For
example, < b > [0-9]< / b > matches a digit in Western alphabets but
< b > \d< / b > matches a digit in < em > any< / em > alphabet.
< p > Note that in most regexp literature sets of characters are called
"character classes".
< p > < a name = "quantifiers" > < / a >
< h3 > Quantifiers
< / h3 >
< a name = "1-3" > < / a > < p > By default an expression is automatically quantified by
< b > {1,1}< / b > , i.e. it should occur exactly once. In the following
list < b > < em > E< / em > < / b > stands for any expression. An expression is a
character or an abbreviation for a set of characters or a set of
characters in square brackets or any parenthesised expression.
< p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > < em > E< / em > ?< / b >
< td valign = "top" > Matches zero or one occurrence of < em > E< / em > . This quantifier
means "the previous expression is optional" since it will
match whether or not the expression occurs in the string. It
is the same as < b > < em > E< / em > {0,1}< / b > . For example < b > dents?< / b >
will match 'dent' and 'dents'.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > < em > E< / em > +< / b >
< td valign = "top" > Matches one or more occurrences of < em > E< / em > . This is the same
as < b > < em > E< / em > {1,MAXINT}< / b > . For example, < b > 0+< / b > will match
'0', '00', '000', etc.
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > < em > E< / em > *< / b >
< td valign = "top" > Matches zero or more occurrences of < em > E< / em > . This is the same
as < b > < em > E< / em > {0,MAXINT}< / b > . The < b > *< / b > quantifier is often
used by a mistake. Since it matches < em > zero< / em > or more
occurrences it will match no occurrences at all. For example
if we want to match strings that end in whitespace and use
the regexp < b > \s*$< / b > we would get a match on every string.
This is because we have said find zero or more whitespace
followed by the end of string, so even strings that don't end
in whitespace will match. The regexp we want in this case is
< b > \s+$< / b > to match strings that have at least one
whitespace at the end.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > < em > E< / em > {n}< / b >
< td valign = "top" > Matches exactly < em > n< / em > occurrences of the expression. This
is the same as repeating the expression < em > n< / em > times. For
example, < b > x{5}< / b > is the same as < b > xxxxx< / b > . It is also
the same as < b > < em > E< / em > {n,n}< / b > , e.g. < b > x{5,5}< / b > .
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > < em > E< / em > {n,}< / b >
< td valign = "top" > Matches at least < em > n< / em > occurrences of the expression. This
is the same as < b > < em > E< / em > {n,MAXINT}< / b > .
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > < em > E< / em > {,m}< / b >
< td valign = "top" > Matches at most < em > m< / em > occurrences of the expression. This
is the same as < b > < em > E< / em > {0,m}< / b > .
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > < em > E< / em > {n,m}< / b >
< td valign = "top" > Matches at least < em > n< / em > occurrences of the expression and at
most < em > m< / em > occurrences of the expression.
< / table > < / center >
< p > (MAXINT is implementation dependent but will not be smaller than
1024.)
< p > If we wish to apply a quantifier to more than just the preceding
character we can use parentheses to group characters together in
an expression. For example, < b > tag+< / b > matches a 't' followed by
an 'a' followed by at least one 'g', whereas < b > (tag)+< / b > matches
at least one occurrence of 'tag'.
< p > Note that quantifiers are "greedy". They will match as much text
as they can. For example, < b > 0+< / b > will match as many zeros as it
can from the first zero it finds, e.g. '2.< u > 000< / u > 5'.
Quantifiers can be made non-greedy, see < a href = "#setMinimal" > setMinimal< / a > ().
< p > < a name = "capturing-text" > < / a >
< h3 > Capturing Text
< / h3 >
< a name = "1-4" > < / a > < p > Parentheses allow us to group elements together so that we can
quantify and capture them. For example if we have the expression
< b > mail|letter|correspondence< / b > that matches a string we know
that < em > one< / em > of the words matched but not which one. Using
parentheses allows us to "capture" whatever is matched within
their bounds, so if we used < b > (mail|letter|correspondence)< / b >
and matched this regexp against the string "I sent you some email"
we can use the < a href = "#cap" > cap< / a > () or < a href = "#capturedTexts" > capturedTexts< / a > () functions to extract the
matched characters, in this case 'mail'.
< p > We can use captured text within the regexp itself. To refer to the
captured text we use < em > backreferences< / em > which are indexed from 1,
the same as for cap(). For example we could search for duplicate
words in a string using < b > \b(\w+)\W+\ 1\b< / b > which means match a
word boundary followed by one or more word characters followed by
one or more non-word characters followed by the same text as the
first parenthesised expression followed by a word boundary.
< p > If we want to use parentheses purely for grouping and not for
capturing we can use the non-capturing syntax, e.g.
< b > (?:green|blue)< / b > . Non-capturing parentheses begin '(?:' and
end ')'. In this example we match either 'green' or 'blue' but we
do not capture the match so we only know whether or not we matched
but not which color we actually found. Using non-capturing
parentheses is more efficient than using capturing parentheses
since the regexp engine has to do less book-keeping.
< p > Both capturing and non-capturing parentheses may be nested.
< p > < a name = "assertions" > < / a >
< h3 > Assertions
< / h3 >
< a name = "1-5" > < / a > < p > Assertions make some statement about the text at the point where
they occur in the regexp but they do not match any characters. In
the following list < b > < em > E< / em > < / b > stands for any expression.
< p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > ^< / b >
< td valign = "top" > The caret signifies the beginning of the string. If you
wish to match a literal < tt > ^< / tt > you must escape it by
writing < b > \ ^< / b > . For example, < b > ^#include< / b > will only
match strings which < em > begin< / em > with the characters '#include'.
(When the caret is the first character of a character set it
has a special meaning, see < a href = "#sets-of-characters" > Sets of
Characters< / a > .)
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > $< / b >
< td valign = "top" > The dollar signifies the end of the string. For example
< b > \d\s*$< / b > will match strings which end with a digit
optionally followed by whitespace. If you wish to match a
literal < tt > $< / tt > you must escape it by writing
< b > \ $< / b > .
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > \ b< / b >
< td valign = "top" > A word boundary. For example the regexp
< b > \ bOK\ b< / b > means match immediately after a word
boundary (e.g. start of string or whitespace) the letter 'O'
then the letter 'K' immediately before another word boundary
(e.g. end of string or whitespace). But note that the
assertion does not actually match any whitespace so if we
write < b > (\ bOK\ b)< / b > and we have a match it will only
contain 'OK' even if the string is "Its < u > OK< / u > now".
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > \ B< / b >
< td valign = "top" > A non-word boundary. This assertion is true wherever
< b > \ b< / b > is false. For example if we searched for
< b > \ Bon\ B< / b > in "Left on" the match would fail (space
and end of string aren't non-word boundaries), but it would
match in "t< u > on< / u > ne".
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > (?=< em > E< / em > )< / b >
< td valign = "top" > Positive lookahead. This assertion is true if the
expression matches at this point in the regexp. For example,
< b > const(?=\ s+char)< / b > matches 'const' whenever it is
followed by 'char', as in 'static < u > const< / u > char *'.
(Compare with < b > const\ s+char< / b > , which matches 'static
< u > const char< / u > *'.)
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > (?!< em > E< / em > )< / b >
< td valign = "top" > Negative lookahead. This assertion is true if the
expression does not match at this point in the regexp. For
example, < b > const(?!\ s+char)< / b > matches 'const' < em > except< / em >
when it is followed by 'char'.
< / table > < / center >
< p > < a name = "wildcard-matching" > < / a >
< h3 > Wildcard Matching (globbing)
< / h3 >
< a name = "1-6" > < / a > < p > Most command shells such as < em > bash< / em > or < em > cmd.exe< / em > support "file
globbing", the ability to identify a group of files by using
wildcards. The < a href = "#setWildcard" > setWildcard< / a > () function is used to switch between
regexp and wildcard mode. Wildcard matching is much simpler than
full regexps and has only four features:
< p > < center > < table cellpadding = "4" cellspacing = "2" border = "0" >
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > c< / b >
< td valign = "top" > Any character represents itself apart from those mentioned
below. Thus < b > c< / b > matches the character < em > c< / em > .
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > ?< / b >
< td valign = "top" > This matches any single character. It is the same as
< b > .< / b > in full regexps.
< tr bgcolor = "#f0f0f0" > < td valign = "top" > < b > *< / b >
< td valign = "top" > This matches zero or more of any characters. It is the
same as < b > .*< / b > in full regexps.
< tr bgcolor = "#d0d0d0" > < td valign = "top" > < b > [...]< / b >
< td valign = "top" > Sets of characters can be represented in square brackets,
similar to full regexps. Within the character class, like
outside, backslash has no special meaning.
< / table > < / center >
< p > For example if we are in wildcard mode and have strings which
contain filenames we could identify HTML files with < b > *.html< / b > .
This will match zero or more characters followed by a dot followed
by 'h', 't', 'm' and 'l'.
< p > < a name = "perl-users" > < / a >
< h3 > Notes for Perl Users
< / h3 >
< a name = "1-7" > < / a > < p > Most of the character class abbreviations supported by Perl are
supported by TQRegExp, see < a href = "#characters-and-abbreviations-for-sets-of-characters" > characters
and abbreviations for sets of characters< / a > .
< p > In TQRegExp, apart from within character classes, < tt > ^< / tt > always
signifies the start of the string, so carets must always be
escaped unless used for that purpose. In Perl the meaning of caret
varies automagically depending on where it occurs so escaping it
is rarely necessary. The same applies to < tt > $< / tt > which in
TQRegExp always signifies the end of the string.
< p > TQRegExp's quantifiers are the same as Perl's greedy quantifiers.
Non-greedy matching cannot be applied to individual quantifiers,
but can be applied to all the quantifiers in the pattern. For
example, to match the Perl regexp < b > ro+?m< / b > requires:
< pre >
TQRegExp rx( "ro+m" );
rx.< a href = "#setMinimal" > setMinimal< / a > ( TRUE );
< / pre >
< p > The equivalent of Perl's < tt > /i< / tt > option is
< a href = "#setCaseSensitive" > setCaseSensitive< / a > (FALSE).
< p > Perl's < tt > /g< / tt > option can be emulated using a < a href = "#cap_in_a_loop" > loop< / a > .
< p > In TQRegExp < b > .< / b > matches any character, therefore all TQRegExp
regexps have the equivalent of Perl's < tt > /s< / tt > option. TQRegExp
does not have an equivalent to Perl's < tt > /m< / tt > option, but this
can be emulated in various ways for example by splitting the input
into lines or by looping with a regexp that searches for newlines.
< p > Because TQRegExp is string oriented there are no \A, \Z or \z
assertions. The \G assertion is not supported but can be emulated
in a loop.
< p > Perl's $& is < a href = "#cap" > cap< / a > (0) or < a href = "#capturedTexts" > capturedTexts< / a > ()[0]. There are no TQRegExp
equivalents for $`, $' or $+. Perl's capturing variables, $1, $2,
... correspond to cap(1) or capturedTexts()[1], cap(2) or
capturedTexts()[2], etc.
< p > To substitute a pattern use < a href = "ntqstring.html#replace" > TQString::replace< / a > ().
< p > Perl's extended < tt > /x< / tt > syntax is not supported, nor are
directives, e.g. (?i), or regexp comments, e.g. (?#comment). On
the other hand, C++'s rules for literal strings can be used to
achieve the same:
< pre >
TQRegExp mark( "\\b" // word boundary
"[Mm]ark" // the word we want to match
);
< / pre >
< p > Both zero-width positive and zero-width negative lookahead
assertions (?=pattern) and (?!pattern) are supported with the same
syntax as Perl. Perl's lookbehind assertions, "independent"
subexpressions and conditional expressions are not supported.
< p > Non-capturing parentheses are also supported, with the same
(?:pattern) syntax.
< p > See < a href = "ntqstringlist.html#split" > TQStringList::split< / a > () and < a href = "ntqstringlist.html#join" > TQStringList::join< / a > () for equivalents
to Perl's split and join functions.
< p > Note: because C++ transforms \ 's they must be written < em > twice< / em > in
code, e.g. < b > \ b< / b > must be written < b > \ \ b< / b > .
< p > < a name = "code-examples" > < / a >
< h3 > Code Examples
< / h3 >
< a name = "1-8" > < / a > < p > < pre >
TQRegExp rx( "^\\d\\d?$" ); // match integers 0 to 99
rx.< a href = "#search" > search< / a > ( "123" ); // returns -1 (no match)
rx.< a href = "#search" > search< / a > ( "-6" ); // returns -1 (no match)
rx.< a href = "#search" > search< / a > ( "6" ); // returns 0 (matched as position 0)
< / pre >
< p > The third string matches '< u > 6< / u > '. This is a simple validation
regexp for integers in the range 0 to 99.
< p > < pre >
TQRegExp rx( "^\\S+$" ); // match strings without whitespace
rx.< a href = "#search" > search< / a > ( "Hello world" ); // returns -1 (no match)
rx.< a href = "#search" > search< / a > ( "This_is-OK" ); // returns 0 (matched at position 0)
< / pre >
< p > The second string matches '< u > This_is-OK< / u > '. We've used the
character set abbreviation '\S' (non-whitespace) and the anchors
to match strings which contain no whitespace.
< p > In the following example we match strings containing 'mail' or
'letter' or 'correspondence' but only match whole words i.e. not
'email'
< p > < pre >
TQRegExp rx( "\\b(mail|letter|correspondence)\\b" );
rx.< a href = "#search" > search< / a > ( "I sent you an email" ); // returns -1 (no match)
rx.< a href = "#search" > search< / a > ( "Please write the letter" ); // returns 17
< / pre >
< p > The second string matches "Please write the < u > letter< / u > ". The
word 'letter' is also captured (because of the parentheses). We
can see what text we've captured like this:
< p > < pre >
< a href = "ntqstring.html" > TQString< / a > captured = rx.cap( 1 ); // captured == "letter"
< / pre >
< p > This will capture the text from the first set of capturing
parentheses (counting capturing left parentheses from left to
right). The parentheses are counted from 1 since < a href = "#cap" > cap< / a > ( 0 ) is the
whole matched regexp (equivalent to '& ' in most regexp engines).
< p > < pre >
TQRegExp rx( "& (?!amp;)" ); // match ampersands but not & amp;
< a href = "ntqstring.html" > TQString< / a > line1 = "This & that";
line1.< a href = "ntqstring.html#replace" > replace< / a > ( rx, "& amp;" );
// line1 == "This & amp; that"
< a href = "ntqstring.html" > TQString< / a > line2 = "His & amp; hers & theirs";
line2.< a href = "ntqstring.html#replace" > replace< / a > ( rx, "& amp;" );
// line2 == "His & amp; hers & amp; theirs"
< / pre >
< p > Here we've passed the TQRegExp to < a href = "ntqstring.html" > TQString< / a > 's replace() function to
replace the matched text with new text.
< p > < pre >
< a href = "ntqstring.html" > TQString< / a > str = "One Eric another Eirik, and an Ericsson."
" How many Eiriks, Eric?";
TQRegExp rx( "\\b(Eric|Eirik)\\b" ); // match Eric or Eirik
int pos = 0; // where we are in the string
int count = 0; // how many Eric and Eirik's we've counted
while ( pos > = 0 ) {
pos = rx.< a href = "#search" > search< / a > ( str, pos );
if ( pos > = 0 ) {
pos++; // move along in str
count++; // count our Eric or Eirik
}
}
< / pre >
< p > We've used the < a href = "#search" > search< / a > () function to repeatedly match the regexp in
the string. Note that instead of moving forward by one character
at a time < tt > pos++< / tt > we could have written < tt > pos += rx.matchedLength()< / tt > to skip over the already matched string. The
count will equal 3, matching 'One < u > Eric< / u > another
< u > Eirik< / u > , and an Ericsson. How many Eiriks, < u > Eric< / u > ?'; it
doesn't match 'Ericsson' or 'Eiriks' because they are not bounded
by non-word boundaries.
< p > One common use of regexps is to split lines of delimited data into
their component fields.
< p > < pre >
str = "Trolltech AS\twww.trolltech.com\tNorway";
< a href = "ntqstring.html" > TQString< / a > company, web, country;
rx.setPattern( "^([^\t]+)\t([^\t]+)\t([^\t]+)$" );
if ( rx.search( str ) != -1 ) {
company = rx.cap( 1 );
web = rx.cap( 2 );
country = rx.cap( 3 );
}
< / pre >
< p > In this example our input lines have the format company name, web
address and country. Unfortunately the regexp is rather long and
not very versatile -- the code will break if we add any more
fields. A simpler and better solution is to look for the
separator, '\t' in this case, and take the surrounding text. The
< a href = "ntqstringlist.html" > TQStringList< / a > split() function can take a separator string or regexp
as an argument and split a string accordingly.
< p > < pre >
< a href = "ntqstringlist.html" > TQStringList< / a > field = TQStringList::< a href = "ntqstringlist.html#split" > split< / a > ( "\t", str );
< / pre >
< p > Here field[0] is the company, field[1] the web address and so on.
< p > To imitate the matching of a shell we can use wildcard mode.
< p > < pre >
TQRegExp rx( "*.html" ); // invalid regexp: * doesn't quantify anything
rx.< a href = "#setWildcard" > setWildcard< / a > ( TRUE ); // now it's a valid wildcard regexp
rx.< a href = "#exactMatch" > exactMatch< / a > ( "index.html" ); // returns TRUE
rx.< a href = "#exactMatch" > exactMatch< / a > ( "default.htm" ); // returns FALSE
rx.< a href = "#exactMatch" > exactMatch< / a > ( "readme.txt" ); // returns FALSE
< / pre >
< p > Wildcard matching can be convenient because of its simplicity, but
any wildcard regexp can be defined using full regexps, e.g.
< b > .*\ .html$< / b > . Notice that we can't match both < tt > .html< / tt > and < tt > .htm< / tt > files with a wildcard unless we use < b > *.htm*< / b > which will
also match 'test.html.bak'. A full regexp gives us the precision
we need, < b > .*\ .html?$< / b > .
< p > TQRegExp can match case insensitively using < a href = "#setCaseSensitive" > setCaseSensitive< / a > (), and
can use non-greedy matching, see < a href = "#setMinimal" > setMinimal< / a > (). By default TQRegExp
uses full regexps but this can be changed with < a href = "#setWildcard" > setWildcard< / a > ().
Searching can be forward with < a href = "#search" > search< / a > () or backward with
< a href = "#searchRev" > searchRev< / a > (). Captured text can be accessed using < a href = "#capturedTexts" > capturedTexts< / a > ()
which returns a string list of all captured strings, or using
< a href = "#cap" > cap< / a > () which returns the captured string for the given index. The
< a href = "#pos" > pos< / a > () function takes a match index and returns the position in the
string where the match was made (or -1 if there was no match).
< p > < p > See also < a href = "qregexpvalidator.html" > TQRegExpValidator< / a > , < a href = "ntqstring.html" > TQString< / a > , < a href = "ntqstringlist.html" > TQStringList< / a > , < a href = "misc.html" > Miscellaneous Classes< / a > , < a href = "shared.html" > Implicitly and Explicitly Shared Classes< / a > , and < a href = "tools.html" > Non-GUI Classes< / a > .
< p > < a name = "member-function-documentation" > < / a >
< hr > < h2 > Member Type Documentation< / h2 >
< h3 class = fn > < a name = "CaretMode-enum" > < / a > TQRegExp::CaretMode< / h3 >
< p > The CaretMode enum defines the different meanings of the caret
(< b > ^< / b > ) in a < a href = "ntqregexp.html#regular-expression" > regular expression< / a > . The possible values are:
< ul >
< li > < tt > TQRegExp::CaretAtZero< / tt > -
The caret corresponds to index 0 in the searched string.
< li > < tt > TQRegExp::CaretAtOffset< / tt > -
The caret corresponds to the start offset of the search.
< li > < tt > TQRegExp::CaretWontMatch< / tt > -
The caret never matches.
< / ul >
< hr > < h2 > Member Function Documentation< / h2 >
< h3 class = fn > < a name = "TQRegExp" > < / a > TQRegExp::TQRegExp ()
< / h3 >
Constructs an empty regexp.
< p > < p > See also < a href = "#isValid" > isValid< / a > () and < a href = "#errorString" > errorString< / a > ().
< h3 class = fn > < a name = "TQRegExp-2" > < / a > TQRegExp::TQRegExp ( const < a href = "ntqstring.html" > TQString< / a > & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )
< / h3 >
Constructs a < a href = "ntqregexp.html#regular-expression" > regular expression< / a > object for the given < em > pattern< / em >
string. The pattern must be given using wildcard notation if < em > wildcard< / em > is TRUE (default is FALSE). The pattern is case
sensitive, unless < em > caseSensitive< / em > is FALSE. Matching is greedy
(maximal), but can be changed by calling < a href = "#setMinimal" > setMinimal< / a > ().
< p > < p > See also < a href = "#setPattern" > setPattern< / a > (), < a href = "#setCaseSensitive" > setCaseSensitive< / a > (), < a href = "#setWildcard" > setWildcard< / a > (), and < a href = "#setMinimal" > setMinimal< / a > ().
< h3 class = fn > < a name = "TQRegExp-3" > < / a > TQRegExp::TQRegExp ( const < a href = "ntqregexp.html" > TQRegExp< / a > & rx )
< / h3 >
Constructs a < a href = "ntqregexp.html#regular-expression" > regular expression< / a > as a copy of < em > rx< / em > .
< p > < p > See also < a href = "#operator-eq" > operator=< / a > ().
< h3 class = fn > < a name = "~TQRegExp" > < / a > TQRegExp::~TQRegExp ()
< / h3 >
Destroys the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > and cleans up its internal data.
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "cap" > < / a > TQRegExp::cap ( int nth = 0 )
< / h3 >
Returns the text captured by the < em > nth< / em > subexpression. The entire
match has index 0 and the parenthesized subexpressions have
indices starting from 1 (excluding non-capturing parentheses).
< p > < pre >
TQRegExp rxlen( "(\\d+)(?:\\s*)(cm|inch)" );
int pos = rxlen.< a href = "#search" > search< / a > ( "Length: 189cm" );
if ( pos > -1 ) {
< a href = "ntqstring.html" > TQString< / a > value = rxlen.< a href = "#cap" > cap< / a > ( 1 ); // "189"
< a href = "ntqstring.html" > TQString< / a > unit = rxlen.< a href = "#cap" > cap< / a > ( 2 ); // "cm"
// ...
}
< / pre >
< p > The order of elements matched by < a href = "#cap" > cap< / a > () is as follows. The first
element, cap(0), is the entire matching string. Each subsequent
element corresponds to the next capturing open left parentheses.
Thus cap(1) is the text of the first capturing parentheses, cap(2)
is the text of the second, and so on.
< p > < a name = "cap_in_a_loop" > < / a >
Some patterns may lead to a number of matches which cannot be
determined in advance, for example:
< p > < pre >
TQRegExp rx( "(\\d+)" );
str = "Offsets: 12 14 99 231 7";
< a href = "ntqstringlist.html" > TQStringList< / a > list;
pos = 0;
while ( pos > = 0 ) {
pos = rx.< a href = "#search" > search< / a > ( str, pos );
if ( pos > -1 ) {
list += rx.< a href = "#cap" > cap< / a > ( 1 );
pos += rx.< a href = "#matchedLength" > matchedLength< / a > ();
}
}
// list contains "12", "14", "99", "231", "7"
< / pre >
< p > < p > See also < a href = "#capturedTexts" > capturedTexts< / a > (), < a href = "#pos" > pos< / a > (), < a href = "#exactMatch" > exactMatch< / a > (), < a href = "#search" > search< / a > (), and < a href = "#searchRev" > searchRev< / a > ().
< p > Examples: < a href = "archivesearch-example.html#x479" > network/archivesearch/archivedialog.ui.h< / a > and < a href = "regexptester-example.html#x2485" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > < a href = "ntqstringlist.html" > TQStringList< / a > < a name = "capturedTexts" > < / a > TQRegExp::capturedTexts ()
< / h3 >
Returns a list of the captured text strings.
< p > The first string in the list is the entire matched string. Each
subsequent list element contains a string that matched a
(capturing) subexpression of the regexp.
< p > For example:
< pre >
TQRegExp rx( "(\\d+)(\\s*)(cm|inch(es)?)" );
int pos = rx.< a href = "#search" > search< / a > ( "Length: 36 inches" );
< a href = "ntqstringlist.html" > TQStringList< / a > list = rx.< a href = "#capturedTexts" > capturedTexts< / a > ();
// list is now ( "36 inches", "36", " ", "inches", "es" )
< / pre >
< p > The above example also captures elements that may be present but
which we have no interest in. This problem can be solved by using
non-capturing parentheses:
< p > < pre >
TQRegExp rx( "(\\d+)(?:\\s*)(cm|inch(?:es)?)" );
int pos = rx.< a href = "#search" > search< / a > ( "Length: 36 inches" );
< a href = "ntqstringlist.html" > TQStringList< / a > list = rx.< a href = "#capturedTexts" > capturedTexts< / a > ();
// list is now ( "36 inches", "36", "inches" )
< / pre >
< p > Note that if you want to iterate over the list, you should iterate
over a copy, e.g.
< pre >
< a href = "ntqstringlist.html" > TQStringList< / a > list = rx.capturedTexts();
TQStringList::Iterator it = list.< a href = "tqvaluelist.html#begin" > begin< / a > ();
while( it != list.< a href = "tqvaluelist.html#end" > end< / a > () ) {
myProcessing( *it );
++it;
}
< / pre >
< p > Some regexps can match an indeterminate number of times. For
example if the input string is "Offsets: 12 14 99 231 7" and the
regexp, < tt > rx< / tt > , is < b > (\ d+)+< / b > , we would hope to get a list of
all the numbers matched. However, after calling
< tt > rx.search(str)< / tt > , < a href = "#capturedTexts" > capturedTexts< / a > () will return the list ( "12",
"12" ), i.e. the entire match was "12" and the first subexpression
matched was "12". The correct approach is to use < a href = "#cap" > cap< / a > () in a < a href = "#cap_in_a_loop" > loop< / a > .
< p > The order of elements in the string list is as follows. The first
element is the entire matching string. Each subsequent element
corresponds to the next capturing open left parentheses. Thus
capturedTexts()[1] is the text of the first capturing parentheses,
capturedTexts()[2] is the text of the second and so on
(corresponding to $1, $2, etc., in some other regexp languages).
< p > < p > See also < a href = "#cap" > cap< / a > (), < a href = "#pos" > pos< / a > (), < a href = "#exactMatch" > exactMatch< / a > (), < a href = "#search" > search< / a > (), and < a href = "#searchRev" > searchRev< / a > ().
< h3 class = fn > bool < a name = "caseSensitive" > < / a > TQRegExp::caseSensitive () const
< / h3 >
Returns TRUE if case sensitivity is enabled; otherwise returns
FALSE. The default is TRUE.
< p > < p > See also < a href = "#setCaseSensitive" > setCaseSensitive< / a > ().
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "errorString" > < / a > TQRegExp::errorString ()
< / h3 >
Returns a text string that explains why a regexp pattern is
invalid the case being; otherwise returns "no error occurred".
< p > < p > See also < a href = "#isValid" > isValid< / a > ().
< p > Example: < a href = "regexptester-example.html#x2486" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "escape" > < / a > TQRegExp::escape ( const < a href = "ntqstring.html" > TQString< / a > & str )< tt > [static]< / tt >
< / h3 >
Returns the string < em > str< / em > with every regexp special character
escaped with a backslash. The special characters are $, (, ), *, +,
., ?, [, \ , ], ^, {, | and }.
< p > Example:
< pre >
s1 = TQRegExp::< a href = "#escape" > escape< / a > ( "bingo" ); // s1 == "bingo"
s2 = TQRegExp::< a href = "#escape" > escape< / a > ( "f(x)" ); // s2 == "f\\(x\\)"
< / pre >
< p > This function is useful to construct regexp patterns dynamically:
< p > < pre >
TQRegExp rx( "(" + TQRegExp::escape(name) +
"|" + TQRegExp::escape(alias) + ")" );
< / pre >
< h3 class = fn > bool < a name = "exactMatch" > < / a > TQRegExp::exactMatch ( const < a href = "ntqstring.html" > TQString< / a > & str ) const
< / h3 >
Returns TRUE if < em > str< / em > is matched exactly by this < a href = "ntqregexp.html#regular-expression" > regular expression< / a > ; otherwise returns FALSE. You can determine how much of
the string was matched by calling < a href = "#matchedLength" > matchedLength< / a > ().
< p > For a given regexp string, R, < a href = "#exactMatch" > exactMatch< / a > ("R") is the equivalent of
< a href = "#search" > search< / a > ("^R$") since exactMatch() effectively encloses the regexp
in the start of string and end of string anchors, except that it
sets matchedLength() differently.
< p > For example, if the regular expression is < b > blue< / b > , then
exactMatch() returns TRUE only for input < tt > blue< / tt > . For inputs < tt > bluebell< / tt > , < tt > blutak< / tt > and < tt > lightblue< / tt > , exactMatch() returns FALSE
and matchedLength() will return 4, 3 and 0 respectively.
< p > Although const, this function sets matchedLength(),
< a href = "#capturedTexts" > capturedTexts< / a > () and < a href = "#pos" > pos< / a > ().
< p > < p > See also < a href = "#search" > search< / a > (), < a href = "#searchRev" > searchRev< / a > (), and < a href = "qregexpvalidator.html" > TQRegExpValidator< / a > .
< h3 class = fn > bool < a name = "isEmpty" > < / a > TQRegExp::isEmpty () const
< / h3 >
Returns TRUE if the pattern string is empty; otherwise returns
FALSE.
< p > If you call < a href = "#exactMatch" > exactMatch< / a > () with an empty pattern on an empty string
it will return TRUE; otherwise it returns FALSE since it operates
over the whole string. If you call < a href = "#search" > search< / a > () with an empty pattern
on < em > any< / em > string it will return the start offset (0 by default)
because the empty pattern matches the 'emptiness' at the start of
the string. In this case the length of the match returned by
< a href = "#matchedLength" > matchedLength< / a > () will be 0.
< p > See < a href = "ntqstring.html#isEmpty" > TQString::isEmpty< / a > ().
< h3 class = fn > bool < a name = "isValid" > < / a > TQRegExp::isValid () const
< / h3 >
Returns TRUE if the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > is valid; otherwise returns
FALSE. An invalid regular expression never matches.
< p > The pattern < b > [a-z< / b > is an example of an invalid pattern, since
it lacks a closing square bracket.
< p > Note that the validity of a regexp may also depend on the setting
of the wildcard flag, for example < b > *.html< / b > is a valid
wildcard regexp but an invalid full regexp.
< p > < p > See also < a href = "#errorString" > errorString< / a > ().
< p > Example: < a href = "regexptester-example.html#x2487" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > int < a name = "match" > < / a > TQRegExp::match ( const < a href = "ntqstring.html" > TQString< / a > & str, int index = 0, int * len = 0, bool indexIsStart = TRUE ) const
< / h3 > < b > This function is obsolete.< / b > It is provided to keep old source working. We strongly advise against using it in new code.
< p > Attempts to match in < em > str< / em > , starting from position < em > index< / em > .
Returns the position of the match, or -1 if there was no match.
< p > The length of the match is stored in < em > *len< / em > , unless < em > len< / em > is a
null pointer.
< p > If < em > indexIsStart< / em > is TRUE (the default), the position < em > index< / em > in
the string will match the start of string anchor, < b > ^< / b > , in the
regexp, if present. Otherwise, position 0 in < em > str< / em > will match.
< p > Use < a href = "#search" > search< / a > () and < a href = "#matchedLength" > matchedLength< / a > () instead of this function.
< p > < p > See also < a href = "ntqstring.html#mid" > TQString::mid< / a > () and < a href = "qconststring.html" > TQConstString< / a > .
< p > Example: < a href = "qmag-example.html#x1791" > qmag/qmag.cpp< / a > .
< h3 class = fn > int < a name = "matchedLength" > < / a > TQRegExp::matchedLength () const
< / h3 >
Returns the length of the last matched string, or -1 if there was
no match.
< p > < p > See also < a href = "#exactMatch" > exactMatch< / a > (), < a href = "#search" > search< / a > (), and < a href = "#searchRev" > searchRev< / a > ().
< p > Examples: < a href = "archivesearch-example.html#x480" > network/archivesearch/archivedialog.ui.h< / a > and < a href = "regexptester-example.html#x2488" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > bool < a name = "minimal" > < / a > TQRegExp::minimal () const
< / h3 >
Returns TRUE if minimal (non-greedy) matching is enabled;
otherwise returns FALSE.
< p > < p > See also < a href = "#setMinimal" > setMinimal< / a > ().
< h3 class = fn > int < a name = "numCaptures" > < / a > TQRegExp::numCaptures () const
< / h3 >
Returns the number of captures contained in the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > .
< p > Example: < a href = "regexptester-example.html#x2489" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > bool < a name = "operator!-eq" > < / a > TQRegExp::operator!= ( const < a href = "ntqregexp.html" > TQRegExp< / a > & rx ) const
< / h3 >
< p > Returns TRUE if this < a href = "ntqregexp.html#regular-expression" > regular expression< / a > is not equal to < em > rx< / em > ;
otherwise returns FALSE.
< p > < p > See also < a href = "#operator-eq-eq" > operator==< / a > ().
< h3 class = fn > < a href = "ntqregexp.html" > TQRegExp< / a > & < a name = "operator-eq" > < / a > TQRegExp::operator= ( const < a href = "ntqregexp.html" > TQRegExp< / a > & rx )
< / h3 >
Copies the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > < em > rx< / em > and returns a reference to the
copy. The case sensitivity, wildcard and minimal matching options
are also copied.
< h3 class = fn > bool < a name = "operator-eq-eq" > < / a > TQRegExp::operator== ( const < a href = "ntqregexp.html" > TQRegExp< / a > & rx ) const
< / h3 >
Returns TRUE if this < a href = "ntqregexp.html#regular-expression" > regular expression< / a > is equal to < em > rx< / em > ;
otherwise returns FALSE.
< p > Two TQRegExp objects are equal if they have the same pattern
strings and the same settings for case sensitivity, wildcard and
minimal matching.
< h3 class = fn > < a href = "ntqstring.html" > TQString< / a > < a name = "pattern" > < / a > TQRegExp::pattern () const
< / h3 >
Returns the pattern string of the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > . The pattern
has either regular expression syntax or wildcard syntax, depending
on < a href = "#wildcard" > wildcard< / a > ().
< p > < p > See also < a href = "#setPattern" > setPattern< / a > ().
< h3 class = fn > int < a name = "pos" > < / a > TQRegExp::pos ( int nth = 0 )
< / h3 >
Returns the position of the < em > nth< / em > captured text in the searched
string. If < em > nth< / em > is 0 (the default), < a href = "#pos" > pos< / a > () returns the position
of the whole match.
< p > Example:
< pre >
TQRegExp rx( "/([a-z]+)/([a-z]+)" );
rx.< a href = "#search" > search< / a > ( "Output /dev/null" ); // returns 7 (position of /dev/null)
rx.< a href = "#pos" > pos< / a > ( 0 ); // returns 7 (position of /dev/null)
rx.< a href = "#pos" > pos< / a > ( 1 ); // returns 8 (position of dev)
rx.< a href = "#pos" > pos< / a > ( 2 ); // returns 12 (position of null)
< / pre >
< p > For zero-length matches, pos() always returns -1. (For example, if
< a href = "#cap" > cap< / a > (4) would return an empty string, pos(4) returns -1.) This is
due to an implementation tradeoff.
< p > < p > See also < a href = "#capturedTexts" > capturedTexts< / a > (), < a href = "#exactMatch" > exactMatch< / a > (), < a href = "#search" > search< / a > (), and < a href = "#searchRev" > searchRev< / a > ().
< h3 class = fn > int < a name = "search" > < / a > TQRegExp::search ( const < a href = "ntqstring.html" > TQString< / a > & str, int offset = 0, < a href = "ntqregexp.html#CaretMode-enum" > CaretMode< / a > caretMode = CaretAtZero ) const
< / h3 >
Attempts to find a match in < em > str< / em > from position < em > offset< / em > (0 by
default). If < em > offset< / em > is -1, the search starts at the last
character; if -2, at the next to last character; etc.
< p > Returns the position of the first match, or -1 if there was no
match.
< p > The < em > caretMode< / em > parameter can be used to instruct whether < b > ^< / b >
should match at index 0 or at < em > offset< / em > .
< p > You might prefer to use < a href = "ntqstring.html#find" > TQString::find< / a > (), < a href = "ntqstring.html#contains" > TQString::contains< / a > () or
even < a href = "ntqstringlist.html#grep" > TQStringList::grep< / a > (). To replace matches use
< a href = "ntqstring.html#replace" > TQString::replace< / a > ().
< p > Example:
< pre >
< a href = "ntqstring.html" > TQString< / a > str = "offsets: 1.23 .50 71.00 6.00";
TQRegExp rx( "\\d*\\.\\d+" ); // primitive floating point matching
int count = 0;
int pos = 0;
while ( (pos = rx.< a href = "#search" > search< / a > (str, pos)) != -1 ) {
count++;
pos += rx.< a href = "#matchedLength" > matchedLength< / a > ();
}
// pos will be 9, 14, 18 and finally 24; count will end up as 4
< / pre >
< p > Although const, this function sets < a href = "#matchedLength" > matchedLength< / a > (),
< a href = "#capturedTexts" > capturedTexts< / a > () and < a href = "#pos" > pos< / a > ().
< p > < p > See also < a href = "#searchRev" > searchRev< / a > () and < a href = "#exactMatch" > exactMatch< / a > ().
< p > Examples: < a href = "archivesearch-example.html#x481" > network/archivesearch/archivedialog.ui.h< / a > and < a href = "regexptester-example.html#x2490" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > int < a name = "searchRev" > < / a > TQRegExp::searchRev ( const < a href = "ntqstring.html" > TQString< / a > & str, int offset = -1, < a href = "ntqregexp.html#CaretMode-enum" > CaretMode< / a > caretMode = CaretAtZero ) const
< / h3 >
Attempts to find a match backwards in < em > str< / em > from position < em > offset< / em > . If < em > offset< / em > is -1 (the default), the search starts at the
last character; if -2, at the next to last character; etc.
< p > Returns the position of the first match, or -1 if there was no
match.
< p > The < em > caretMode< / em > parameter can be used to instruct whether < b > ^< / b >
should match at index 0 or at < em > offset< / em > .
< p > Although const, this function sets < a href = "#matchedLength" > matchedLength< / a > (),
< a href = "#capturedTexts" > capturedTexts< / a > () and < a href = "#pos" > pos< / a > ().
< p > < b > Warning:< / b > Searching backwards is much slower than searching
forwards.
< p > < p > See also < a href = "#search" > search< / a > () and < a href = "#exactMatch" > exactMatch< / a > ().
< h3 class = fn > void < a name = "setCaseSensitive" > < / a > TQRegExp::setCaseSensitive ( bool sensitive )
< / h3 >
Sets case sensitive matching to < em > sensitive< / em > .
< p > If < em > sensitive< / em > is TRUE, < b > \ .txt$< / b > matches < tt > readme.txt< / tt > but
not < tt > README.TXT< / tt > .
< p > < p > See also < a href = "#caseSensitive" > caseSensitive< / a > ().
< p > Example: < a href = "regexptester-example.html#x2491" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > void < a name = "setMinimal" > < / a > TQRegExp::setMinimal ( bool minimal )
< / h3 >
Enables or disables minimal matching. If < em > minimal< / em > is FALSE,
matching is greedy (maximal) which is the default.
< p > For example, suppose we have the input string "We must be
< b>bold< /b>, very < b>bold< /b>!" and the pattern
< b > < b>.*< /b>< / b > . With the default greedy (maximal) matching,
the match is "We must be < u > < b>bold< /b>, very
< b>bold< /b>< / u > !". But with minimal (non-greedy) matching the
first match is: "We must be < u > < b>bold< /b>< / u > , very
< b>bold< /b>!" and the second match is "We must be < b>bold< /b>,
very < u > < b>bold< /b>< / u > !". In practice we might use the pattern
< b > < b>[^< ]+< /b>< / b > instead, although this will still fail for
nested tags.
< p > < p > See also < a href = "#minimal" > minimal< / a > ().
< p > Examples: < a href = "archivesearch-example.html#x482" > network/archivesearch/archivedialog.ui.h< / a > and < a href = "regexptester-example.html#x2492" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > void < a name = "setPattern" > < / a > TQRegExp::setPattern ( const < a href = "ntqstring.html" > TQString< / a > & pattern )
< / h3 >
Sets the pattern string to < em > pattern< / em > . The case sensitivity,
wildcard and minimal matching options are not changed.
< p > < p > See also < a href = "#pattern" > pattern< / a > ().
< h3 class = fn > void < a name = "setWildcard" > < / a > TQRegExp::setWildcard ( bool wildcard )
< / h3 >
Sets the wildcard mode for the < a href = "ntqregexp.html#regular-expression" > regular expression< / a > . The default is
FALSE.
< p > Setting < em > wildcard< / em > to TRUE enables simple shell-like wildcard
matching. (See < a href = "#wildcard-matching" > wildcard matching
(globbing)< / a > .)
< p > For example, < b > r*.txt< / b > matches the string < tt > readme.txt< / tt > in
wildcard mode, but does not match < tt > readme< / tt > .
< p > < p > See also < a href = "#wildcard" > wildcard< / a > ().
< p > Example: < a href = "regexptester-example.html#x2493" > regexptester/regexptester.cpp< / a > .
< h3 class = fn > bool < a name = "wildcard" > < / a > TQRegExp::wildcard () const
< / h3 >
Returns TRUE if wildcard mode is enabled; otherwise returns FALSE.
The default is FALSE.
< p > < p > See also < a href = "#setWildcard" > setWildcard< / a > ().
<!-- eof -->
< hr > < p >
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