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Setting up, then displaying contents, of a hash
Hashes example from a Well House Consultants training course
More on Hashes [link]
Source code: ha1 Module: P211
=head1 Sample data antonia Perl XML PHP Tcl/Tk MySQL barbara Tcl/Tk Lua Ruby Java [and so on] With data like this, you'll want to be able to ask questions like "does Barbara know Perl" and "what skills does Xena have", rather than "what does the 10th person in my file know?". In other words, you'll want to look things up by a key rather than by a value. In Perl, you should use a HASH for this purpose - a hash is a collection of scalars, each keyed by another scalar. Hashes differ from lists - the other colelction type in Perl - as follows: a) hashes are keyed by any scalar, not by number b) hashes are unordered (i.e. not sorted/sortable) c) hashes are referred to with a % not an @ d) hash members are accessed with {} and not [] =cut open (FH,"../requests.xyz") or die(); while ($line = <FH>) { chop($line); ($name,$skills) = split(/\s+/,$line,2); # The hash is called %stab - but no need to # declare it as it's automatically created $stab{$name} = $skills; } # You can't sort a hash but you CAN sort a list # of the keys .... @nems = reverse(sort byvalue (keys %stab)); # ... and the step through each keyed item in turn foreach $name (@nems) { print "$name --- $stab{$name}\n"; } print "There are ",@nems+0," people\n"; # Sort routine - inputs are always $a and $b # and output is -ve / 0 / +ve to indicate which # way the two values in $a and $b should be ordered sub byvalue { # Following print useful for training! # print "$a .......... $b\n"; $stab{$a} cmp $stab{$b}; } __END__ Sample Output Dorothy:p82 grahamellis$ perl ha1 petra --- XML Tcl/Tk Lua Perl Ruby gloria --- XML Perl Tcl/Tk MySQL margaret --- XML Perl Ruby MySQL Tcl/Tk jenny --- XML Perl Ruby Lua yuri --- XML PHP Perl Tcl/Tk delia --- XML PHP Java Lua tina --- Tcl/Tk Ruby Java ken --- Tcl/Tk Python Java Perl sally --- Tcl/Tk Perl XML MySQL steve --- Tcl/Tk Perl PHP Ruby quentin --- Tcl/Tk Perl PHP Ruby nina --- Tcl/Tk Perl Lua Ruby barbara --- Tcl/Tk Lua Ruby Java victor --- Ruby Perl Tcl/Tk MySQL william --- Ruby Perl PHP ed --- Ruby Perl Java PHP yollanda --- Ruby MySQL Tcl/Tk zoe --- Ruby Lua Perl PHP florence --- Ruby Lua PHP Java ivan --- Ruby Java Perl Tcl/Tk MySQL barry --- Python XML Java Perl PHP adam --- Python Tcl/Tk Perl MySQL antonia --- Perl XML PHP Tcl/Tk MySQL kerry --- Perl Tcl/Tk Ruby MySQL wendy --- Perl Tcl/Tk Lua MySQL david --- Perl Tcl/Tk Java charles --- Perl Ruby MySQL Tcl/Tk iris --- Perl MySQL Java Tcl/Tk tommy --- Perl Java XML cherry --- Perl Java Ruby MySQL morris --- Perl Java PHP Tcl/Tk len --- Perl Java MySQL Ruby john --- PHP XML Java Perl hazel --- PHP Python Perl Ruby Lua leane --- PHP Python Lua Perl Java nigel --- PHP Python Java Perl harry --- PHP Python Java rita --- PHP Lua Ruby Perl peter --- PHP Java Perl xavier --- PHP Java Perl orpheus --- MySQL Ruby Tcl/Tk XML olivia --- MySQL Python Lua PHP ethel --- MySQL Perl Tcl/Tk Lua fred --- MySQL Perl Java XML uva --- MySQL Perl Java PHP zachary --- MySQL Java Tcl/Tk queenie --- Lua Ruby Perl MySQL graham --- Lua Perl Tcl/Tk rupert --- Java Python MySQL venus --- Java Perl Ruby Lua xena --- Java Perl PHP Lua XML ulsyees --- Java PHP Perl There are 52 people Dorothy:p82 grahamellis$ Learn about this subject
This module and example are covered on the following public courses:
* Perl Programming * Perl bootcamp * Learning to program in Perl * Perl Programming Also available on on site courses for larger groups Books covering this topic
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Other Examples
This example comes from our "Hashes" training module. You'll find a description of the topic and some
other closely related examples on the "Hashes" module index page.
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