QRegExp(3qt)QRegExp(3qt)NAME
QRegExp - Pattern matching using regular expressions
SYNOPSIS
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 ) const
int searchRev ( const QString & str, int offset = -1, CaretMode
caretMode = CaretAtZero ) const
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 )
DESCRIPTION
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:
<center>.nf
</center>
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.
In case of multi-threaded programming, note that QRegExp depends on
QThreadStorage internally. For that reason, QRegExp should only be used
with threads started with QThread, i.e. not with threads started with
platform-specific APIs.
Introduction
Characters and Abbreviations for Sets of Characters
Sets of Characters
Quantifiers
Capturing Text
Assertions
Wildcard Matching (globbing)
Notes for Perl Users
Code Examples
Introduction
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 $, do not
match any characters.
If you've seen regexps elsewhere they may have looked different from
the ones above. This is because some sets of characters and some
quantifiers are so common that they have special symbols to represent
them. [0-9] can be replaced with the symbol \d. The quantifier to match
exactly one occurrence, {1,1}, can be replaced with the expression
itself. This means that x{1,1} is exactly the same as x alone. So our 0
to 99 matcher could be written ^\d{1,2}$. 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 '&'. 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
\b(Eric|Eirik)\b and \bEi?ri[ck]\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
<center>.nf
Element
───────────────────────────────────────────────────────────────
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). \0ooo
(i.e., \zero ooo) matches the ASCII/Latin-1 character
corresponding to the octal number ooo (between 0 and 0377).
</center>
Note that the C++ compiler transforms backslashes in strings so to
include a \ in a regexp you will need to enter it twice, i.e.
\\.
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.
<center>.nf
</center>
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".
Quantifiers
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.
<center>.nf
─────────────────────────────────────────────────────────────
means "the previous expression is optional" since it will
match whether or not the expression occurs in the string. It
is the same as
as
as
is the same as repeating the expression n times. For
example,
is the same as
is the same as
</center>
(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+\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
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.
<center>.nf
</center>
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:
<center>.nf
────────────
below. Thus
same as
</center>
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, $2,
capturedTexts()[2], etc.
To substitute a pattern use QString::replace().
Perl's extended /x syntax is not supported, nor are directives, e.g.
(?i), or regexp comments, e.g. (?#comment). On the other hand, C++'s
rules for literal strings can be used to achieve the same:
QRegExp mark( "\\b" // word boundary
"[Mm]ark" // the word we want to match
);
Both zero-width positive and zero-width negative lookahead assertions
(?=pattern) and (?!pattern) are supported with the same syntax as Perl.
Perl's lookbehind assertions, "independent" subexpressions and
conditional expressions are not supported.
Non-capturing parentheses are also supported, with the same (?:pattern)
syntax.
See QStringList::split() and QStringList::join() for equivalents to
Perl's split and join functions.
Note: because C++ transforms \'s they must be written twice in
code, e.g. \b must be written \\b.
Code Examples
QRegExp rx( "^\\d\\d?$" ); // 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 &
QString line1 = "This & that";
line1.replace( rx, "&" );
// line1 == "This & that"
QString line2 = "His & hers & theirs";
line2.replace( rx, "&" );
// line2 == "His & hers & 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. .*\.html$.
Notice that we can't match both .html and .htm files with a wildcard
unless we use *.htm* which will also match 'test.html.bak'. A full
regexp gives us the precision we need, .*\.html?$.
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
QRegExp::CaretMode
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.
MEMBER FUNCTION DOCUMENTATIONQRegExp::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 parentheses).
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 example:
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().
Examples:
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 );
++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
(\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().
Example: regexptester/regexptester.cpp.
QString QRegExp::escape ( const QString & str ) [static]
Returns the string str with every regexp special character escaped with
a backslash. The special characters are $, (, ), *, +,
Example:
s1 = QRegExp::escape( "bingo" ); // s1 == "bingo"
s2 = QRegExp::escape( "f(x)" ); // s2 == "f\\(x\\)"
This function is useful to construct regexp patterns dynamically:
QRegExp rx( "(" + QRegExp::escape(name) +
"|" + QRegExp::escape(alias) + ")" );
bool QRegExp::exactMatch ( const QString & str ) const
Returns TRUE if str is matched exactly by this regular expression;
otherwise returns FALSE. You can determine how much of the string was
matched by calling matchedLength().
For a given regexp string, R, exactMatch("R") is the equivalent of
search("^R$") 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 bracket.
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().
Example: regexptester/regexptester.cpp.
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 match.
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().
Examples:
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.
Example: regexptester/regexptester.cpp.
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.
Example:
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 ) const
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 offset.
You might prefer to use QString::find(), QString::contains() or even
QStringList::grep(). To replace matches use QString::replace().
Example:
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 ) {
count++;
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().
Examples:
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; 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 offset.
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, \.txt$ matches readme.txt but not README.TXT.
See also caseSensitive().
Example: regexptester/regexptester.cpp.
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().
Examples:
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 readme.
See also wildcard().
Example: regexptester/regexptester.cpp.
bool QRegExp::wildcard () const
Returns TRUE if wildcard mode is enabled; otherwise returns FALSE. The
default is FALSE.
See also setWildcard().
SEE ALSO
http://doc.trolltech.com/qregexp.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
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http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
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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 (3.3.8).
Trolltech AS 2 February 2007 QRegExp(3qt)