view release on metacpan or  search on metacpan

cheats.txt  view on Meta::CPAN

## Perl Modules - XML::LibXML
#############################################################

# Parse and find specific nodes/elements in an xml file
# "//Page" means to look recursively down for a "Page" element
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); print "$_\n\n" for $d->findnodes("//Page")'

# Parse xml file. Find all "PageTable" elements
# Select all PageTableProperty inside.
# Print out the value of the PageTableName   (Use @ to find an attribute instead of a value)
# Print out the value (using ->to_literal)
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); for($d->findnodes("//PageTable")){ ($p)=$_->findnodes("PageTableProperty"); print map $_->to_literal, $p->findnodes("\@PageTableName") }' | head

# Parse xml file. Find all "PageTable" elements
# findvalue is like findnode and then to_literal. Use it when you expect a single node
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); for($d->findnodes("//PageTable")){ ($p)=$_->findnodes("PageTableProperty"); print $p->findvalue("\@PageTableName") }'
#
# Same thing but using getAttribute() DOM method.
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); for($d->findnodes("//PageTable")){ ($p)=$_->findnodes("./PageTableProperty"); print $p->getAttribute("PageTableName") }'
#
# Can also use the tied hash accessing approach $p->{ATTRIBUTE}
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); for($d->findnodes("//PageTable")){ ($p)=$_->findnodes("PageTableProperty"); print $p->{PageTableName} }'

# Parse xml file. Find all "PageTable" elements
# Print only the actuator page
perl -MXML::LibXML -le '$d=XML::LibXML->load_xml(location => "my.xml"); for($d->findnodes("//PageTable")){ ($p)=$_->findnodes("./PageTableProperty"); $v=$p->findvalue("\@PageTableName"); print if $v eq "ACTUATOR" }'

# Process HTML using XML::LibXML
# Does not load badly formated files without these options:
#     recover
#     suppress_errors
perl -MXML::LibXML -le '$d=XML::LibXML->load_html(location => "index.html", recover => 1, suppress_errors => 1); print $d'

# XML Process big files. Save memory
perl -MXML::LibXML::Reader -le '$d=XML::LibXML::Reader->new(location => "xml"); printf "%-10s %-10s %-10s %-10s\n", $d->nodeType, $d->depth, $d->name, $d->getAttribute("code") while $d->read'

# Pull out parts of of a list
perl -MXML::LibXML -le '$d=XML::LibXML->load_html(location => "OSRS", recover => 1, suppress_errors => 1); @t = $d->findnodes(q(//table[@class="wikitable infobox"])); @t = grep { $_->findvalue(q(tr[th/a/@title="Members"]/td)) =~ /No/} @t; print for @...

# Issues with XML::LibXML. Cannot parse control characters (except \n or \r)
perl -MXML::LibXML -E 'my $v = XML::LibXML->load_xml( string => "<div>\f</div>")'
#
# HTML::Entities does not help.
perl -MXML::LibXML -MHTML::Entities -E 'my $v = XML::LibXML->load_xml( string => encode_entities("<div>\f</div>", "\f"))'
#
# Same:
perl -MXML::LibXML -E 'my $v = XML::LibXML->load_xml( string => "<div>&#12;</div>")'


#############################################################
## Perl Modules - XML::Simple
#############################################################

# Read xml file and print out the structure
perl -MXML::Simple -MData::Dumper -le '$xs=XML::Simple->new; print Dumper($xs->XMLin("embraer.xml"))'

# Print the structure of an xml file while reading the input
perl -MXML::Simple -MData::Dumper -le '$d=XML::Simple::XMLin($ARGV[0]//die"\nSyntax: tool xmlfile\n\n"); print Dumper($d)'

# XML::Simple example
perl -Me -MXML::Simple -e 'my $xml = XML::Simple->new; say $xml->XMLout( "hey", AttrIndent => 1, NoAttr => 1, KeyAttr => [], RootName => "RootElement" )'

# Why use XML::Simple AND XML::LibXML together
perl -Me -MXML::Simple -MXML::LibXML -e 'my $x = XML::Simple->new->XMLout( "hey\f", AttrIndent => 1, NoAttr => 1, KeyAttr => [], RootName => "RootElement" ); say(XML::LibXML->load_xml( string => $x))'
:1: parser error : PCDATA invalid Char value 12
<RootElement>hey
                </RootElement>
                ^
perl -Me -MXML::Simple -MXML::LibXML -e 'my $x = XML::Simple->new->XMLout( "hey\f", AttrIndent => 1, NoAttr => 1, KeyAttr => [], RootName => "RootElement" ); say(XML::LibXML->load_xml( string => "abc"))'


#############################################################
## Perl Modules - YAML::XS
#############################################################

# Simple example of converting between yaml and a data structure.
perl -MYAML::XS -E '$yml = Dump [1..3]; $arr = Load $yml'


#############################################################
## Perl Book - Learning Perl Examples
#############################################################

# Exercise 2.1 (Learning Perl)
perl -le '$r=12.5; $pi=3.141592654; $c=2*$r*$pi; print $c'

# Exercise 2.2 (Learning Perl)
perl -le 'print "Enter radius: "; $r=<STDIN>; $pi=3.141592654; $c=2*$r*$pi; print $c'

# Exercise 2.3 (Learning Perl)
perl -le 'print "Enter radius: "; $r=<STDIN>; if($r < 0){ $r = 0 } $pi=3.141592654; $c=2*$r*$pi; print $c'

# Exercise 2.4 (Learning Perl)
perl -le 'print "Enter Num1: "; chomp($num1=<STDIN>); print "Enter Num2: "; chomp($num2=<STDIN>); print "$num1 * $num2 = ", ($num1 * $num2)'

# Exercise 2.5 (Learning Perl)
perl -le 'print "Enter String: "; chomp($string=<STDIN>); print "Enter num: "; chomp($num=<STDIN>); print $string x $num'


#############################################################
## Perl6 Programs (Rakudo)
#############################################################

# Setup/install/compile rakudo (perl6)
# 1. Get Latest
rm -f ~/rakudo/setup/index.html*
read -sp "Password: " PASSWORD
echo "$PASSWORD" | perl -ple 's/(\W)/ sprintf "%%%x", ord($1) /eg'
wget http://rakudo.org/downloads/star/ -P ~/rakudo/setup
ls ~/rakudo/setup/index.html | perl -MHTML::Tree -lne 'print HTML::Tree->new_from_file($_)->look_down(class => "ext-gz")->attr("href")'
basename `$LATEST`

# Setup/install/compile rakudo (perl6)
# 2. Download
read -sp "Password: " PASSWORD
echo "$PASSWORD" | perl -ple 's/(\W)/ sprintf "%%%x", ord($1) /eg'
wget http://rakudo.org/downloads/star/$LATEST -P ~/rakudo/setup

# Setup/install/compile rakudo (perl6)
# 3. Compile
tar -xvzf rakudo.tar.gz
cd rakudo
perl Configure.pl --backend=moar --gen-moar
make
make install

# Rational numbers issues with languages
ruby -e 'puts 0.1 + 0.2 == 0.3'
python -c 'print 0.1 + 0.2 == 0.3'