📄 pattern matching.mht

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Subject: Pattern Matching
Date: Wed, 29 Apr 2009 09:26:19 +0800
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<H1 class=3DSECT1><A name=3DPATTERNMATCHING>6. Pattern Matching</A></H1>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN285>Introduction</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT>match<FONT color=3D#00ffff>(</FONT> $string, $pattern <FONT =
color=3D#00ffff>);</FONT>
subst<FONT color=3D#00ffff>(</FONT> $string, $pattern, $replacement =
<FONT color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$meadow =3D~ <FONT color=3D#ff7f50>m</FONT>/sheep/<FONT =
color=3D#00ffff>;</FONT>   <FONT color=3D#bebebe># True if $meadow =
contains "sheep"
</FONT>$meadow !~ <FONT color=3D#ff7f50>m</FONT>/sheep/<FONT =
color=3D#00ffff>;</FONT>   <FONT color=3D#bebebe># True if $meadow =
doesn't contain "sheep"
</FONT>$meadow =3D~ <FONT color=3D#ff7f50>s</FONT>/old/new/<FONT =
color=3D#00ffff>;</FONT> <FONT color=3D#bebebe># Replace "old" with =
"new" in $meadow
#-----------------------------
# Fine bovines demand fine toreadors.
# Muskoxen are a polar ovibovine species.
# Grooviness went out of fashion decades ago.
#-----------------------------
# Ovines are found typically in oviaries.
#-----------------------------
</FONT><FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#00ffff>(</FONT>$meadow =3D~ /\bovines?\b/i<FONT =
color=3D#00ffff>)</FONT> <FONT color=3D#00ffff>{</FONT> <FONT =
color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Here be =
sheep!"</FONT> <FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$string =3D <FONT color=3D#00cd00>"good food"</FONT><FONT =
color=3D#00ffff>;</FONT>
$string =3D~ <FONT color=3D#ff7f50>s</FONT>/o*/e/<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
# good food
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# geod food
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# geed food
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# geed feed
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# ged food
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# ged fed
#</FONT><FONT color=3D#43cd80> </FONT><FONT color=3D#bebebe>
# egood food
#-----------------------------
#% echo ababacaca | perl -ne 'print "$&amp;\n" if /(a|ba|b)+(a|ac)+/'
#ababa
#-----------------------------
#% echo ababacaca |</FONT><FONT color=3D#43cd80> </FONT><FONT =
color=3D#bebebe>
#    awk 'match($0,/(a|ba|b)+(a|ac)+/) { print substr($0, RSTART, =
RLENGTH) }'
#ababacaca
#-----------------------------
</FONT><FONT color=3D#ffa500>while</FONT> <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#ff7f50>m</FONT>/<FONT =
color=3D#00ffff>(</FONT>\d+<FONT color=3D#00ffff>)</FONT>/g<FONT =
color=3D#00ffff>)</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Found =
number $1\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#cdad00>@numbers</FONT> =3D <FONT =
color=3D#ff7f50>m</FONT>/<FONT color=3D#00ffff>(</FONT>\d+<FONT =
color=3D#00ffff>)</FONT>/g<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$digits =3D <FONT color=3D#00cd00>"123456789"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#cdad00>@nonlap</FONT> =3D $digits =3D~ /<FONT =
color=3D#00ffff>(</FONT>\d\d\d<FONT color=3D#00ffff>)</FONT>/g<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#cdad00>@yeslap</FONT> =3D $digits =3D~ /<FONT =
color=3D#00ffff>(</FONT>?=3D<FONT color=3D#00ffff>(</FONT>\d\d\d<FONT =
color=3D#00ffff>))</FONT>/g<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT =
color=3D#00cd00>"Non-overlapping:  </FONT><FONT =
color=3D#cdad00>@nonlap</FONT><FONT color=3D#00cd00>\n"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Overlapping:   =
   </FONT><FONT color=3D#cdad00>@yeslap</FONT><FONT =
color=3D#00cd00>\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe># Non-overlapping:  123 456 789
</FONT>
<FONT color=3D#bebebe># Overlapping:      123 234 345 456 567 678 789
#-----------------------------
</FONT>$string =3D <FONT color=3D#00cd00>"And little lambs eat =
ivy"</FONT><FONT color=3D#00ffff>;</FONT>
$string =3D~ /l<FONT color=3D#00ffff>[</FONT>^<FONT =
color=3D#ff7f50>s</FONT><FONT color=3D#00ffff>]</FONT>*<FONT =
color=3D#ff7f50>s</FONT>/<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"($`) ($&amp;) =
($')\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe># (And ) (little lambs) ( eat ivy)
#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN288>Copying and Substituting =
Simultaneously</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT>$dst =3D $src<FONT color=3D#00ffff>;</FONT>
$dst =3D~ <FONT color=3D#ff7f50>s</FONT>/this/that/<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#00ffff>(</FONT>$dst =3D $src<FONT =
color=3D#00ffff>)</FONT> =3D~ <FONT =
color=3D#ff7f50>s</FONT>/this/that/<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
# strip to basename
</FONT><FONT color=3D#00ffff>(</FONT>$progname =3D $<FONT =
color=3D#cdcd00>0</FONT><FONT color=3D#00ffff>)</FONT>        =3D~ <FONT =
color=3D#ff7f50>s</FONT>!^.*/!!<FONT color=3D#00ffff>;</FONT>

<FONT color=3D#bebebe># Make All Words Title-Cased
</FONT><FONT color=3D#00ffff>(</FONT>$capword  =3D $word<FONT =
color=3D#00ffff>)</FONT>     =3D~ <FONT color=3D#ff7f50>s</FONT>/<FONT =
color=3D#00ffff>(</FONT>\w+<FONT color=3D#00ffff>)</FONT>/\u\L$<FONT =
color=3D#cdcd00>1</FONT>/g<FONT color=3D#00ffff>;</FONT>

<FONT color=3D#bebebe># /usr/man/man3/foo.1 changes to =
/usr/man/cat3/foo.1
</FONT><FONT color=3D#00ffff>(</FONT>$catpage  =3D $manpage<FONT =
color=3D#00ffff>)</FONT>  =3D~ <FONT color=3D#ff7f50>s</FONT>/man<FONT =
color=3D#00ffff>(</FONT>?=3D\d<FONT color=3D#00ffff>)</FONT>/cat/<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#cdad00>@bindirs</FONT> =3D <FONT =
color=3D#ff7f50>qw</FONT><FONT color=3D#00ffff>(</FONT> /usr/bin /bin =
/usr/<FONT color=3D#ffa500>local</FONT>/bin <FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#ffa500>for</FONT> <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@libdirs</FONT> =3D <FONT =
color=3D#cdad00>@bindirs</FONT><FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT> <FONT color=3D#ff7f50>s</FONT>/bin/lib/ <FONT =
color=3D#00ffff>}</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"</FONT><FONT =
color=3D#cdad00>@libdirs</FONT><FONT color=3D#00cd00>\n"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe># /usr/lib /lib /usr/local/lib
#-----------------------------
</FONT><FONT color=3D#00ffff>(</FONT>$a =3D  $b<FONT =
color=3D#00ffff>)</FONT> =3D~ <FONT color=3D#ff7f50>s</FONT>/<FONT =
color=3D#98fb98>x</FONT>/<FONT color=3D#ff7f50>y</FONT>/g<FONT =
color=3D#00ffff>;</FONT>      <FONT color=3D#bebebe># copy $b and then =
change $a
</FONT> $a =3D <FONT color=3D#00ffff>(</FONT>$b  =3D~ <FONT =
color=3D#ff7f50>s</FONT>/<FONT color=3D#98fb98>x</FONT>/<FONT =
color=3D#ff7f50>y</FONT>/g<FONT color=3D#00ffff>);</FONT>     <FONT =
color=3D#bebebe># change $b, count goes in $a
#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN291>Matching Letters</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#00ffff>(</FONT>$var =3D~ /^<FONT =
color=3D#00ffff>[</FONT>A-Za<FONT color=3D#b2dfee>-z</FONT><FONT =
color=3D#00ffff>]</FONT>+$/<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#bebebe># it is purely alphabetic
</FONT><FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>locale</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>if</FONT> <FONT color=3D#00ffff>(</FONT>$var =3D~ =
/^<FONT color=3D#00ffff>[</FONT>^\W\d_<FONT =
color=3D#00ffff>]</FONT>+$/<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"var is =
purely alphabetic\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>locale</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>use</FONT> <FONT color=3D#b2dfee>POSIX</FONT> =
<FONT color=3D#00cd00>'locale_h'</FONT><FONT color=3D#00ffff>;</FONT>

<FONT color=3D#bebebe># the following locale string might be different =
on your system
</FONT><FONT color=3D#ffa500>unless</FONT> <FONT =
color=3D#00ffff>(</FONT>setlocale<FONT color=3D#00ffff>(</FONT>LC_ALL, =
<FONT color=3D#00cd00>"fr_CA.ISO8859-1"</FONT><FONT =
color=3D#00ffff>))</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>die</FONT> <FONT color=3D#00cd00>"couldn't set =
locale to French Canadian\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>

<FONT color=3D#ffa500>while</FONT> <FONT =
color=3D#00ffff>(</FONT>&lt;DATA&gt;<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>chomp</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#00ffff>(</FONT>/^<FONT color=3D#00ffff>[</FONT>^\W\d_<FONT =
color=3D#00ffff>]</FONT>+$/<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
        <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"$_: =
alphabetic\n"</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#00ffff>}</FONT> <FONT color=3D#ffa500>else</FONT> =
<FONT color=3D#00ffff>{</FONT>
        <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"$_: =
line noise\n"</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#00ffff>}</FONT>
<FONT color=3D#00ffff>}</FONT>

<FONT color=3D#bebebe>#__END__
#silly
#fa=E7ade
#co=F6perate
#ni=F1o
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