Home Man
Today's Posts

Linux & Unix Commands - Search Man Pages

RedHat 9 (Linux i386) - man page for qregexp (redhat section 3qt)

QRegExp(3qt)									     QRegExp(3qt)

       QRegExp - Pattern matching using regular expressions

       All the functions in this class are reentrant when Qt is built with thread support.</p>

       #include <qregexp.h>

   Public Members
       enum CaretMode { CaretAtZero, CaretAtOffset, CaretWontMatch }
       QRegExp ()
       QRegExp ( const QString & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )
       QRegExp ( const QRegExp & rx )
       ~QRegExp ()
       QRegExp & operator= ( const QRegExp & rx )
       bool operator== ( const QRegExp & rx ) const
       bool operator!= ( const QRegExp & rx ) const
       bool isEmpty () const
       bool isValid () const
       QString pattern () const
       void setPattern ( const QString & pattern )
       bool caseSensitive () const
       void setCaseSensitive ( bool sensitive )
       bool wildcard () const
       void setWildcard ( bool wildcard )
       bool minimal () const
       void setMinimal ( bool minimal )
       bool exactMatch ( const QString & str ) const
       int match ( const QString & str, int index = 0, int * len = 0, bool indexIsStart = TRUE )
	   const  (obsolete)
       int search ( const QString & str, int offset = 0, CaretMode caretMode = CaretAtZero )
       int searchRev ( const QString & str, int offset = -1, CaretMode caretMode = CaretAtZero )
       int matchedLength () const
       int numCaptures () const
       QStringList capturedTexts ()
       QString cap ( int nth = 0 )
       int pos ( int nth = 0 )
       QString errorString ()

   Static Public Members
       QString escape ( const QString & str )

       The QRegExp class provides pattern matching using regular expressions.

       Regular expressions, or "regexps", provide a way to find patterns within text. This is
       useful in many contexts, for example:



       We present a very brief introduction to regexps, a description of Qt's regexp language,
       some code examples, and finally the function documentation itself. QRegExp is modeled on
       Perl's regexp language, and also fully supports Unicode. QRegExp 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 Mastering Regular Expressions: Powerful Techniques for Perl and Other
       Tools by Jeffrey E. Friedl, ISBN 1565922573.

       Experienced regexp users may prefer to skip the introduction and go directly to the
       relevant information.


       Characters and Abbreviations for Sets of Characters

       Sets of Characters


       Capturing Text


       Wildcard Matching (globbing)

       Notes for Perl Users

	Code Examples

       Regexps are built up from expressions, quantifiers, and assertions. The simplest form of
       expression is simply a character, e.g. x or 5. An expression can also be a set of
       characters. For example, [ABCD], will match an A or a B or a C or a D. As a shorthand we
       could write this as [A-D]. If we want to match any of the captital letters in the English
       alphabet we can write [A-Z]. A quantifier tells the regexp engine how many occurrences of
       the expression we want, e.g. x{1,1} means match an x which occurs at least once and at
       most once. We'll look at assertions and more complex expressions later.

       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 <b> and its closing </b> you can only use a
       regexp if you know that these tags are not nested; the html fragment, <b>bold
       <b>bolder</b></b> 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.

       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 [0-9]{1,1} 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 [0-9]{1,2} 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 within a string. To ensure that
       we match against the whole string we must use the anchor assertions. We need ^ (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 $ (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 ^[0-9]{1,2}$. Note that assertions, such as ^ and $, do not match any

       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. [0-9] can be replaced with the symbol \d. The
       quantifier to match exactly one occurrence, {1,1}, can be replaced with the expression
       itself. This means that x{1,1} is exactly the same as x alone. So our 0 to 99 matcher
       could be written ^\d{1,2}$. Another way of writing it would be ^\d\d{0,1}$, i.e. from the
       start of the string match a digit followed by zero or one digits. In practice most people
       would write it ^\d\d?$. The ? is a shorthand for the quantifier {0,1}, i.e. a minimum of
       no occurrences a maximum of one occurrence. This is used to make an expression optional.
       The regexp ^\d\d?$ means "from the beginning of the string match one digit followed by
       zero or one digits and then the end of the string".

       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, m{1,1}a{1,1}i{1,1}l{1,1}, but since each expression itself
       is automatically quantified by {1,1} we can simply write this as mail; an 'm' followed by
       an 'a' followed by an 'i' followed by an 'l'. The symbol '|' (bar) is used for
       alternation, so our regexp now becomes mail|letter|correspondence which means match 'mail'
       or 'letter' or '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, (mail|letter|correspondence). Parentheses have two effects, firstly they
       group expressions together and secondly they identify parts of the regexp that we wish to
       capture. 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 "word boundary": \b(mail|letter|correspondence)\b. This regexp
       means "match a word boundary followed by the expression in parentheses followed by another
       word boundary". The \b assertion matches at a position in the regexp not a character 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.

       For our third example we want to replace ampersands with the HTML entity '&amp;'. The
       regexp to match is simple: &, 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: &(?!amp;). The
       negative lookahead assertion is introduced with '(?!' and finishes at the ')'. It means
       that the text it contains, 'amp;' in our example, must not follow the expression that
       preceeds it.

       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 &#92;b(Eric|Eirik)&#92;b and &#92;bEi?ri[ck]&#92;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'.

       We will implement some the examples above in the code examples section.

Characters and Abbreviations for Sets of Characters


       regexp meaning. Thus

       itself except where mentioned below. For example if you
       wished to match a literal caret at the beginning of a string
       you would write

       hexadecimal number hhhh (between 0x0000 and 0xFFFF). &#92;0ooo
       (i.e., \zero ooo) matches the ASCII/Latin-1 character
       corresponding to the octal number ooo (between 0 and 0377).


       Note that the C++ compiler transforms backslashes in strings so to include a &#92; in a
       regexp you will need to enter it twice, i.e. &#92;&#92;.

Sets of Characters
       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.



       Using the predefined character set abbreviations is more portable than using character
       ranges across platforms and languages. For example, [0-9] matches a digit in Western
       alphabets but \d matches a digit in any alphabet.

       Note that in most regexp literature sets of characters are called" character classes".

       By default an expression is automatically quantified by {1,1}, i.e. it should occur
       exactly once. In the following list E 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.


       means "the previous expression is optional" since it will
       match whether or not the expression occurs in the string. It
       is the same as



       is the same as repeating the expression n times. For

       is the same as

       is the same as


       (MAXINT is implementation dependent but will not be smaller than 1024.)

       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, tag+ matches a 't'
       followed by an 'a' followed by at least one 'g', whereas (tag)+ matches at least one
       occurrence of 'tag'.

       Note that quantifiers are "greedy". They will match as much text as they can. For example,
       0+ 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 setMinimal().

Capturing Text
       Parentheses allow us to group elements together so that we can quantify and capture them.
       For example if we have the expression mail|letter|correspondence that matches a string we
       know that one of the words matched but not which one. Using parentheses allows us to
       "capture" whatever is matched within their bounds, so if we used
       (mail|letter|correspondence) and matched this regexp against the string "I sent you some
       email" we can use the cap() or capturedTexts() functions to extract the matched
       characters, in this case 'mail'.

       We can use captured text within the regexp itself. To refer to the captured text we use
       backreferences which are indexed from 1, the same as for cap(). For example we could
       search for duplicate words in a string using \b(\w+)\W+&#92;1\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.

       If we want to use parentheses purely for grouping and not for capturing we can use the
       non-capturing syntax, e.g. (?:green|blue). 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.

       Both capturing and non-capturing parentheses may be nested.

       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 E stands for any expression.



Wildcard Matching (globbing)
       Most command shells such as bash or cmd.exe support "file globbing", the ability to
       identify a group of files by using wildcards. The setWildcard() function is used to switch
       between regexp and wildcard mode. Wildcard matching is much simpler than full regexps and
       has only four features:


       below. Thus

       same as


       For example if we are in wildcard mode and have strings which contain filenames we could
       identify HTML files with *.html. This will match zero or more characters followed by a dot
       followed by 'h', 't', 'm' and 'l'.

Notes for Perl Users
       Most of the character class abbreviations supported by Perl are supported by QRegExp, see
       characters and abbreviations for sets of characters.

       In QRegExp, apart from within character classes, ^ 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 $ which in QRegExp always signifies the end of the string.

       QRegExp'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 ro+?m requires:

	   QRegExp rx( "ro+m" );
	   rx.setMinimal( TRUE );

       The equivalent of Perl's /i option is setCaseSensitive(FALSE).

       Perl's /g option can be emulated using a loop.

       In QRegExp . matches any character, therefore all QRegExp regexps have the equivalent of
       Perl's /s option. QRegExp does not have an equivalent to Perl's /m 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.

       Because QRegExp is string oriented there are no \A, \Z or \z assertions. The \G assertion
       is not supported but can be emulated in a loop.

       Perl's $& is cap(0) or capturedTexts()[0]. There are no QRegExp equivalents for $`, $' or
       $+. Perl's capturing variables, $1, $2, capturedTexts()[2], etc.

       To substitute a pattern use QString::replace().

       Perl's extended /x 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:

	   QRegExp mark( "\\b" // word boundary
			 "[Mm]ark" // the word we want to match

       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.

       Non-capturing parentheses are also supported, with the same (?:pattern) syntax.

       See QStringList::split() and QStringList::join() for equivalents to Perl's split and join

       Note: because C++ transforms &#92;'s they must be written twice in code, e.g. &#92;b must
       be written &#92;&#92;b.

Code Examples
	   QRegExp rx( "^\\d\\d?$" );  // match integers 0 to 99
	   rx.search( "123" );	       // returns -1 (no match)
	   rx.search( "-6" );	       // returns -1 (no match)
	   rx.search( "6" );	       // returns 0 (matched as position 0)

       The third string matches '<u>6</u>'. This is a simple validation regexp for integers in
       the range 0 to 99.

	   QRegExp rx( "^\\S+$" );     // match strings without whitespace
	   rx.search( "Hello world" ); // returns -1 (no match)
	   rx.search( "This_is-OK" );  // returns 0 (matched at position 0)

       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.

       In the following example we match strings containing 'mail' or 'letter' or
       'correspondence' but only match whole words i.e. not 'email'

	   QRegExp rx( "\\b(mail|letter|correspondence)\\b" );
	   rx.search( "I sent you an email" );	   // returns -1 (no match)
	   rx.search( "Please write the letter" ); // returns 17

       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:

	   QString captured = rx.cap( 1 ); // captured == "letter"

       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 cap( 0 ) is
       the whole matched regexp (equivalent to '&' in most regexp engines).

	   QRegExp rx( "&(?!amp;)" );	   // match ampersands but not &amp;
	   QString line1 = "This & that";
	   line1.replace( rx, "&amp;" );
	   // line1 == "This &amp; that"
	   QString line2 = "His &amp; hers & theirs";
	   line2.replace( rx, "&amp;" );
	   // line2 == "His &amp; hers &amp; theirs"

       Here we've passed the QRegExp to QString's replace() function to replace the matched text
       with new text.

	   QString str = "One Eric another Eirik, and an Ericsson."
			   " How many Eiriks, Eric?";
	   QRegExp 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.search( str, pos );
	       if ( pos >= 0 ) {
		   pos++;      // move along in str
		   count++;    // count our Eric or Eirik

       We've used the search() function to repeatedly match the regexp in the string. Note that
       instead of moving forward by one character at a time pos++ we could have written pos +=
       rx.matchedLength() 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.

       One common use of regexps is to split lines of delimited data into their component fields.

	   str = "Trolltech AS\twww.trolltech.com\tNorway";
	   QString 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 );

       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 QStringList split() function can take a
       separator string or regexp as an argument and split a string accordingly.

	   QStringList field = QStringList::split( "\t", str );

       Here field[0] is the company, field[1] the web address and so on.

       To imitate the matching of a shell we can use wildcard mode.

	   QRegExp rx( "*.html" );	   // invalid regexp: * doesn't quantify anything
	   rx.setWildcard( TRUE );	   // now it's a valid wildcard regexp
	   rx.exactMatch( "index.html" );  // returns TRUE
	   rx.exactMatch( "default.htm" ); // returns FALSE
	   rx.exactMatch( "readme.txt" );  // returns FALSE

       Wildcard matching can be convenient because of its simplicity, but any wildcard regexp can
       be defined using full regexps, e.g. .*&#92;.html$. Notice that we can't match both .html
       and .htm files with a wildcard unless we use *.htm* which will also match 'test.html.bak'.
       A full regexp gives us the precision we need, .*&#92;.html?$.

       QRegExp can match case insensitively using setCaseSensitive(), and can use non-greedy
       matching, see setMinimal(). By default QRegExp uses full regexps but this can be changed
       with setWildcard(). Searching can be forward with search() or backward with searchRev().
       Captured text can be accessed using capturedTexts() which returns a string list of all
       captured strings, or using cap() which returns the captured string for the given index.
       The pos() function takes a match index and returns the position in the string where the
       match was made (or -1 if there was no match).

       See also QRegExpValidator, QString, QStringList, Miscellaneous Classes, Implicitly and
       Explicitly Shared Classes, and Non-GUI Classes.

   Member Type Documentation
       The CaretMode enum defines the different meanings of the caret (^) in a regular
       expression. The possible values are:

       QRegExp::CaretAtZero - The caret corresponds to index 0 in the searched string.

       QRegExp::CaretAtOffset - The caret corresponds to the start offset of the search.

       QRegExp::CaretWontMatch - The caret never matches.

QRegExp::QRegExp ()
       Constructs an empty regexp.

       See also isValid() and errorString().

QRegExp::QRegExp ( const QString & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )
       Constructs a regular expression object for the given pattern string. The pattern must be
       given using wildcard notation if wildcard is TRUE (default is FALSE). The pattern is case
       sensitive, unless caseSensitive is FALSE. Matching is greedy (maximal), but can be changed
       by calling setMinimal().

       See also setPattern(), setCaseSensitive(), setWildcard(), and setMinimal().

QRegExp::QRegExp ( const QRegExp & rx )
       Constructs a regular expression as a copy of rx.

       See also operator=().

QRegExp::~QRegExp ()
       Destroys the regular expression and cleans up its internal data.

QString QRegExp::cap ( int nth = 0 )
       Returns the text captured by the nth subexpression. The entire match has index 0 and the
       parenthesized subexpressions have indices starting from 1 (excluding non-capturing

	   QRegExp rxlen( "(\\d+)(?:\\s*)(cm|inch)" );
	   int pos = rxlen.search( "Length: 189cm" );
	   if ( pos > -1 ) {
	       QString value = rxlen.cap( 1 ); // "189"
	       QString unit = rxlen.cap( 2 );  // "cm"
	       // ...

       The order of elements matched by cap() 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.

       Some patterns may lead to a number of matches which cannot be determined in advance, for

	   QRegExp rx( "(\\d+)" );
	   str = "Offsets: 12 14 99 231 7";
	   QStringList list;
	   pos = 0;
	   while ( pos >= 0 ) {
	       pos = rx.search( str, pos );
	       if ( pos > -1 ) {
		   list += rx.cap( 1 );
		   pos	+= rx.matchedLength();
	   // list contains "12", "14", "99", "231", "7"

       See also capturedTexts(), pos(), exactMatch(), search(), and searchRev().

QStringList QRegExp::capturedTexts ()
       Returns a list of the captured text strings.

       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.

       For example:

	       QRegExp rx( "(\\d+)(\\s*)(cm|inch(es)?)" );
	       int pos = rx.search( "Length: 36 inches" );
	       QStringList list = rx.capturedTexts();
	       // list is now ( "36 inches", "36", " ", "inches", "es" )

       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:

	       QRegExp rx( "(\\d+)(?:\\s*)(cm|inch(?:es)?)" );
	       int pos = rx.search( "Length: 36 inches" );
	       QStringList list = rx.capturedTexts();
	       // list is now ( "36 inches", "36", "inches" )

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

	       QStringList list = rx.capturedTexts();
	       QStringList::Iterator it = list.begin();
	       while( it != list.end() ) {
		   myProcessing( *it );

       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, rx, is (&#92;d+)+, we would hope to get a
       list of all the numbers matched. However, after calling rx.search(str), capturedTexts()
       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 cap() in a loop.

       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).

       See also cap(), pos(), exactMatch(), search(), and searchRev().

bool QRegExp::caseSensitive () const
       Returns TRUE if case sensitivity is enabled; otherwise returns FALSE. The default is TRUE.

       See also setCaseSensitive().

QString QRegExp::errorString ()
       Returns a text string that explains why a regexp pattern is invalid the case being;
       otherwise returns "no error occurred".

       See also isValid().

QString QRegExp::escape ( const QString & str ) [static]
       Returns the string str with every regexp special character escaped with a backslash. The
       special characters are $, (, ), *, +,


	    s1 = QRegExp::escape( "bingo" );   // s1 == "bingo"
	    s2 = QRegExp::escape( "f(x)" );    // s2 == "f\\(x\\)"

       This function is useful to construct regexp patterns dynamically:

	   QRegExp rx( "(" + QRegExp::escape(name) +
		       "|" + QRegExp::escape(alias) + ")" );

bool QRegExp::exactMatch ( const QString & str ) const
       Returns TRUE if str is matched exactly by this regular expression; otherwise returns
       FALSE. You can determine how much of the string was matched by calling matchedLength().

       For a given regexp string, R, exactMatch("R") is the equivalent of search("^R$") since
       exactMatch() effectively encloses the regexp in the start of string and end of string
       anchors, except that it sets matchedLength() differently.

       For example, if the regular expression is blue, then exactMatch() returns TRUE only for
       input blue. For inputs bluebell, blutak and lightblue, exactMatch() returns FALSE and
       matchedLength() will return 4, 3 and 0 respectively.

       Although const, this function sets matchedLength(), capturedTexts() and pos().

       See also search(), searchRev(), and QRegExpValidator.

bool QRegExp::isEmpty () const
       Returns TRUE if the pattern string is empty; otherwise returns FALSE.

       If you call exactMatch() 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 search()
       with an empty pattern on any 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 matchedLength() will be 0.

       See QString::isEmpty().

bool QRegExp::isValid () const
       Returns TRUE if the regular expression is valid; otherwise returns FALSE. An invalid
       regular expression never matches.

       The pattern [a-z is an example of an invalid pattern, since it lacks a closing square

       Note that the validity of a regexp may also depend on the setting of the wildcard flag,
       for example *.html is a valid wildcard regexp but an invalid full regexp.

       See also errorString().

int QRegExp::match ( const QString & str, int index = 0, int * len = 0, bool indexIsStart = TRUE
       ) const
       This function is obsolete. It is provided to keep old source working. We strongly advise
       against using it in new code.

       Attempts to match in str, starting from position index. Returns the position of the match,
       or -1 if there was no match.

       The length of the match is stored in *len, unless len is a null pointer.

       If indexIsStart is TRUE (the default), the position index in the string will match the
       start of string anchor, ^, in the regexp, if present. Otherwise, position 0 in str will

       Use search() and matchedLength() instead of this function.

       See also QString::mid() and QConstString.

       Example: qmag/qmag.cpp.

int QRegExp::matchedLength () const
       Returns the length of the last matched string, or -1 if there was no match.

       See also exactMatch(), search(), and searchRev().

bool QRegExp::minimal () const
       Returns TRUE if minimal (non-greedy) matching is enabled; otherwise returns FALSE.

       See also setMinimal().

int QRegExp::numCaptures () const
       Returns the number of captures contained in the regular expression.

bool QRegExp::operator!= ( const QRegExp & rx ) const
       Returns TRUE if this regular expression is not equal to rx; otherwise returns FALSE.

       See also operator==().

QRegExp &; QRegExp::operator= ( const QRegExp & rx )
       Copies the regular expression rx and returns a reference to the copy. The case
       sensitivity, wildcard and minimal matching options are also copied.

bool QRegExp::operator== ( const QRegExp & rx ) const
       Returns TRUE if this regular expression is equal to rx; otherwise returns FALSE.

       Two QRegExp objects are equal if they have the same pattern strings and the same settings
       for case sensitivity, wildcard and minimal matching.

QString QRegExp::pattern () const
       Returns the pattern string of the regular expression. The pattern has either regular
       expression syntax or wildcard syntax, depending on wildcard().

       See also setPattern().

int QRegExp::pos ( int nth = 0 )
       Returns the position of the nth captured text in the searched string. If nth is 0 (the
       default), pos() returns the position of the whole match.


	   QRegExp rx( "/([a-z]+)/([a-z]+)" );
	   rx.search( "Output /dev/null" );    // returns 7 (position of /dev/null)
	   rx.pos( 0 ); 		       // returns 7 (position of /dev/null)
	   rx.pos( 1 ); 		       // returns 8 (position of dev)
	   rx.pos( 2 ); 		       // returns 12 (position of null)

       For zero-length matches, pos() always returns -1. (For example, if cap(4) would return an
       empty string, pos(4) returns -1.) This is due to an implementation tradeoff.

       See also capturedTexts(), exactMatch(), search(), and searchRev().

int QRegExp::search ( const QString & str, int offset = 0, CaretMode caretMode = CaretAtZero )
       Attempts to find a match in str from position offset (0 by default). If offset is -1, the
       search starts at the last character; if -2, at the next to last character; etc.

       Returns the position of the first match, or -1 if there was no match.

       The caretMode parameter can be used to instruct whether ^ should match at index 0 or at

       You might prefer to use QString::find(), QString::contains() or even QStringList::grep().
       To replace matches use QString::replace().


	       QString str = "offsets: 1.23 .50 71.00 6.00";
	       QRegExp rx( "\\d*\\.\\d+" );    // primitive floating point matching
	       int count = 0;
	       int pos = 0;
	       while ( (pos = rx.search(str, pos)) != -1 ) {
		   pos += rx.matchedLength();
	       // pos will be 9, 14, 18 and finally 24; count will end up as 4

       Although const, this function sets matchedLength(), capturedTexts() and pos().

       See also searchRev() and exactMatch().

int QRegExp::searchRev ( const QString & str, int offset = -1, CaretMode caretMode = CaretAtZero
       ) const
       Attempts to find a match backwards in str from position offset. If offset is -1 (the
       default), the search starts at the last character; if -2, at the next to last character;

       Returns the position of the first match, or -1 if there was no match.

       The caretMode parameter can be used to instruct whether ^ should match at index 0 or at

       Although const, this function sets matchedLength(), capturedTexts() and pos().

       Warning: Searching backwards is much slower than searching forwards.

       See also search() and exactMatch().

void QRegExp::setCaseSensitive ( bool sensitive )
       Sets case sensitive matching to sensitive.

       If sensitive is TRUE, &#92;.txt$ matches readme.txt but not README.TXT.

       See also caseSensitive().

void QRegExp::setMinimal ( bool minimal )
       Enables or disables minimal matching. If minimal is FALSE, matching is greedy (maximal)
       which is the default.

       For example, suppose we have the input string "We must be <b>bold</b>, very <b>bold</b>!"
       and the pattern <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> instead, although this will still fail for nested tags.

       See also minimal().

void QRegExp::setPattern ( const QString & pattern )
       Sets the pattern string to pattern. The case sensitivity, wildcard and minimal matching
       options are not changed.

       See also pattern().

void QRegExp::setWildcard ( bool wildcard )
       Sets the wildcard mode for the regular expression. The default is FALSE.

       Setting wildcard to TRUE enables simple shell-like wildcard matching. (See wildcard
       matching (globbing).)

       For example, r*.txt matches the string readme.txt in wildcard mode, but does not match

       See also wildcard().

bool QRegExp::wildcard () const
       Returns TRUE if wildcard mode is enabled; otherwise returns FALSE. The default is FALSE.

       See also setWildcard().

       http://doc.trolltech.com/qregexp.html http://www.trolltech.com/faq/tech.html

       Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.

       Generated automatically from the source code.

       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.	Good bug reports help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
       provided as a convenience for those users who prefer man pages, although this format is
       not officially supported by Trolltech.

       If you find errors in this manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qregexp.3qt) and the Qt version (3.1.1).

Trolltech AS				 9 December 2002			     QRegExp(3qt)

All times are GMT -4. The time now is 02:56 PM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
Show Password