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<HTML><HEAD><TITLE>Recipe 6.9. Matching Shell Globs as Regular Expressions (Perl Cookbook)</TITLE><METANAME="DC.title"CONTENT="Perl Cookbook"><METANAME="DC.creator"CONTENT="Tom Christiansen & Nathan Torkington"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1999-07-02T01:34:21Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-243-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch06_01.htm"TITLE="6. Pattern Matching"><LINKREL="prev"HREF="ch06_09.htm"TITLE="6.8. Extracting a Range of Lines"><LINKREL="next"HREF="ch06_11.htm"TITLE="6.10. Speeding Up Interpolated Matches"></HEAD><BODYBGCOLOR="#FFFFFF"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl Cookbook"><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><p><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch06_09.htm"TITLE="6.8. Extracting a Range of Lines"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 6.8. Extracting a Range of Lines"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch06_01.htm"TITLE="6. Pattern Matching"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch06_11.htm"TITLE="6.10. Speeding Up Interpolated Matches"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 6.10. Speeding Up Interpolated Matches"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch06-97251">6.9. Matching Shell Globs as Regular Expressions<ACLASS="indexterm"NAME="ch06-idx-1000007611-0"></A><ACLASS="indexterm"NAME="ch06-idx-1000007611-1"></A><ACLASS="indexterm"NAME="ch06-idx-1000007611-2"></A><ACLASS="indexterm"NAME="ch06-idx-1000007611-3"></A></A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch06-pgfId-1069">Problem</A></H3><PCLASS="para">You want to allow users to specify matches using traditional shell wildcards, not full Perl regular expressions. Wildcards are easier to type than full regular expressions for simple cases.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch06-pgfId-1075">Solution</A></H3><PCLASS="para">Use the following subroutine to convert four shell wildcard characters into their equivalent regular expression; all other characters will be quoted to render them literals.</P><PRECLASS="programlisting">sub glob2pat { my $globstr = shift; my %patmap = ( '*' => '.*', '?' => '.', '[' => '[', ']' => ']', ); $globstr =~ s{(.)} { $patmap{$1} || "\Q$1" }ge; return '^' . $globstr . '$';}</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch06-pgfId-1103">Discussion</A></H3><PCLASS="para">A Perl pattern is not the same as a shell wildcard pattern. The shell's <CODECLASS="literal">*.*</CODE> is not a valid regular expression. Its meaning as a pattern would be <CODECLASS="literal">/^.*\..*$/</CODE>, which is admittedly much less fun to type.</P><PCLASS="para">The function given in the Solution makes these conversions for you, following the standard wildcard rules used by the <CODECLASS="literal">glob</CODE> built-in.</P><TABLECLASS="informaltable"BORDER="1"CELLPADDING="3"><TBODYCLASS="tbody"><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><BCLASS="emphasis.bold">Shell</B></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><BCLASS="emphasis.bold">Perl</B></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">list.?</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^list\..$</CODE></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">project.*</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^project\..*$</CODE></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">*old</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^.*old$</CODE></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">type*.[ch]</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^type.*\.[ch]$</CODE></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">*.*</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^.*\..*$</CODE></P></TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">*</CODE></P></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><PCLASS="para"><CODECLASS="literal">^.*$</CODE></P></TD></TR></TBODY></TABLE><PCLASS="para">In the shell, the rules are different. The entire pattern is implicitly anchored at the ends. A question mark maps into any character, an asterisk is any amount of anything, and brackets are character ranges. Everything else is normal.</P><PCLASS="para">Most shells do more than simple one-directory globbing. For instance, you can say <CODECLASS="literal">*/*</CODE> to mean "all the files in all the subdirectories of the current directory." Furthermore, most shells don't list files whose names begin with a period, unless you explicitly put that leading period into your glob pattern. Our <CODECLASS="literal">glob2pat</CODE> function doesn't do these things - if you need them, use the File::KGlob module from CPAN.<ACLASS="indexterm"NAME="ch06-idx-1000007613-0"></A><ACLASS="indexterm"NAME="ch06-idx-1000007613-1"></A><ACLASS="indexterm"NAME="ch06-idx-1000007613-2"></A><ACLASS="indexterm"NAME="ch06-idx-1000007613-3"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch06-pgfId-1129">See Also</A></H3><PCLASS="para">Your system's <ICLASS="filename">csh</I> (1) and <ICLASS="filename">ksh </I>(1) manpages; the <CODECLASS="literal">glob</CODE> function in <ICLASS="filename">perlfunc </I>(1) and <ACLASS="olink"HREF="../prog/ch03_01.htm">Chapter 3</A> of <ACLASS="citetitle"HREF="../prog/index.htm"TITLE="Programming Perl"><CITECLASS="citetitle">Programming Perl</CITE></A>; the documentation for the CPAN module Glob::DosGlob; the "I/O Operators" section of <ICLASS="filename">perlop </I>(1) and the <ACLASS="olink"HREF="../prog/ch02_03.htm#PERL2-CH-2-SECT-3.7.3">"Filename globbing operator"</A> section of <ACLASS="olink"HREF="../prog/ch02_01.htm">Chapter 2</A> of <ACLASS="citetitle"HREF="../prog/index.htm"TITLE="Programming Perl"><CITECLASS="citetitle">Programming Perl</CITE></A>; we talk more about globbing in <ACLASS="xref"HREF="ch09_07.htm"TITLE="Globbing, or Getting a List of Filenames Matching a Pattern">Recipe 9.6</A></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch06_09.htm"TITLE="6.8. 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