\hypertarget{qore_regex_qore_regex_intro}{}\doxysection{Qore Regular Expression Introduction}\label{qore_regex_qore_regex_intro}
Regular expression functionality in Qore is provided by \href{http://www.pcre.org}{\texttt{ PCRE\+: Perl-\/\+Compatible Regular Expression library}}.

Using this library, Qore implements regular expression pattern matching using very simple syntax with semantics similar to those of \href{http://www.perl.org}{\texttt{ Perl 5}}. One difference between Qore and Perl to keep in mind is that \mbox{\hyperlink{qore_regex_qore_regex_backreferences}{backreferences}} in Qore are referenced as {\ttfamily \$1}, {\ttfamily \$2}, {\ttfamily \$3}, etc which differs from Perl\textquotesingle{}s syntax (which uses numbered backslashes instead).

\begin{DoxyParagraph}{Examples\+:}

\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# call process() if the string starts with an alphanumeric character}}
\DoxyCodeLine{\textcolor{keywordflow}{if} (str =\string~ /\string^[[:alnum:]]/)}
\DoxyCodeLine{    process(str);}

\end{DoxyCode}
 
\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# example of using regular expressions in a switch statement}}
\DoxyCodeLine{switch (str) \{}
\DoxyCodeLine{    case /\string^[\string^[:alnum:]]/: \textcolor{keywordflow}{return} \textcolor{keyword}{True};}
\DoxyCodeLine{    case /\string^[0-\/9]/: \textcolor{keywordflow}{return} \textcolor{keyword}{False};}
\DoxyCodeLine{    default: throw \textcolor{stringliteral}{"{}ERROR"{}}, \mbox{\hyperlink{group__string__functions_ga7a74be141f814ef286046c367b21091c}{sprintf}}(\textcolor{stringliteral}{"{}invalid string \%y"{}}, str);}
\DoxyCodeLine{\}}

\end{DoxyCode}
 
\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# regular expression substitution + ignore case \& global options}}
\DoxyCodeLine{str =\string~ s/abc/xyz/gi;}

\end{DoxyCode}
 
\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# prefix all non-\/alphanumeric characters with a backslash}}
\DoxyCodeLine{str =\string~ s/([\string^[:alnum:]])/\(\backslash\)\(\backslash\)\$1/g;}

\end{DoxyCode}
 
\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# regular expression substring extraction}}
\DoxyCodeLine{*list l = (str =\string~ x/(?:(\(\backslash\)w+):(\(\backslash\)w+):)(\(\backslash\)w+)/);}

\end{DoxyCode}

\end{DoxyParagraph}
\hypertarget{qore_regex_qore_regex_operators}{}\doxysection{Qore Regular Expression Operators}\label{qore_regex_qore_regex_operators}
The following is a list of operators based on regular expressions (or similar to regular expressions in the case of the transliteration operator).

{\bfseries{Regular Expression Operators}}  \tabulinesep=1mm
\begin{longtabu}spread 0pt [c]{*{2}{|X[-1]}|}
\hline
{\bfseries{Operator}} &{\bfseries{Description}}  \\\cline{1-2}
\mbox{\hyperlink{operators_regex_match_operator}{Regular Expression Match Operator (=$\sim$)}} &Returns \mbox{\hyperlink{basic_data_types_True}{True}} if the regular expression matches a string  \\\cline{1-2}
\mbox{\hyperlink{operators_regex_no_match_operator}{Regular Expression No Match Operator (!$\sim$)}} &Returns \mbox{\hyperlink{basic_data_types_True}{True}} if the regular expression does not match a string  \\\cline{1-2}
\mbox{\hyperlink{operators_regex_subst_operator}{Regular Expression Substitution Operator}} &Substitutes text in a string based on matching a regular expression  \\\cline{1-2}
\mbox{\hyperlink{operators_regex_extract_operator}{Regular Expression Pattern Extraction Operator}} &Returns a list of substrings in a string based on matching patterns defined by a regular expression  \\\cline{1-2}
\mbox{\hyperlink{operators_transliteration_operator}{Transliteration Operator}} &Not a regular expression operator; transliterates one or more characters to other characters in a string  \\\cline{1-2}
\end{longtabu}


See the table below for valid regular expression options.\hypertarget{qore_regex_qore_regex_options}{}\doxysubsection{Qore Regular Expression Operator Options}\label{qore_regex_qore_regex_options}
{\bfseries{Regular Expression Options}}  \tabulinesep=1mm
\begin{longtabu}spread 0pt [c]{*{2}{|X[-1]}|}
\hline
{\bfseries{Option}} &{\bfseries{Description}}  \\\cline{1-2}
{\ttfamily i}  &Ignores case when matching  \\\cline{1-2}
{\ttfamily m}  &makes start-\/of-\/line ({\ttfamily $^\wedge$}) or end-\/of-\/line ({\ttfamily \$}) match after or before any newline in the subject string  \\\cline{1-2}
{\ttfamily s}  &makes a dot ({\ttfamily .}) match a newline character  \\\cline{1-2}
{\ttfamily x}  &ignores whitespace characters and enables comments prefixed by {\ttfamily \#}  \\\cline{1-2}
{\ttfamily u}  &extends Posix character matching to Unicode characters  \\\cline{1-2}
{\ttfamily g}  &makes global substitutions or global extractions (only applicable with the substitution and extraction operators)  \\\cline{1-2}
\end{longtabu}
\hypertarget{qore_regex_qore_regex_functions}{}\doxysection{Qore Regular Expression Functions}\label{qore_regex_qore_regex_functions}
The following is a list of functions providing regular expression functionality where the pattern may be given at run-\/time\+:

{\bfseries{Regular Expression Functions}}  \tabulinesep=1mm
\begin{longtabu}spread 0pt [c]{*{2}{|X[-1]}|}
\hline
{\bfseries{Function}} &{\bfseries{Description}}  \\\cline{1-2}
\mbox{\hyperlink{group__string__functions_ga7804f63df9b181e0bacb465eb912feb9}{regex()}} &Returns \mbox{\hyperlink{basic_data_types_True}{True}} if the regular expression matches a string  \\\cline{1-2}
\mbox{\hyperlink{group__string__functions_gad8963269da93fe1ebaa179dab8d315fa}{regex\+\_\+subst()}} &Substitutes a pattern in a string based on regular expressions and returns the new string  \\\cline{1-2}
\mbox{\hyperlink{group__string__functions_ga9f8c21f961daa29578dcfd596f5871ff}{regex\+\_\+extract()}} &Returns a list of substrings in a string based on matching patterns defined by a regular expression  \\\cline{1-2}
\end{longtabu}
\hypertarget{qore_regex_qore_regex_backreferences}{}\doxysubsection{Qore Regular Expression Backreferences}\label{qore_regex_qore_regex_backreferences}
\mbox{\hyperlink{namespace_qore}{Qore}} uses {\ttfamily \$}{\itshape num} for backreferences in regular expression substitution expressions. The first backreference is {\ttfamily \$1}, the second \$2, and so on.

\begin{DoxyParagraph}{Example}

\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# prefix all non-\/alphanumeric characters with a backslash}}
\DoxyCodeLine{str =\string~ s/([\string^[:alnum:]])/\(\backslash\)\(\backslash\)\$1/g;}

\end{DoxyCode}
 
\begin{DoxyCode}{0}
\DoxyCodeLine{\textcolor{comment}{\# remove parentheses from string at the beginning of the line}}
\DoxyCodeLine{str =\string~ s/\string^\(\backslash\)((.*)\(\backslash\))/\$1/;}

\end{DoxyCode}
 
\end{DoxyParagraph}