Re: Stumped with a Posix/Perl Question

[Ken Irving <fnkci@uaf.edu>]

On Thu, Apr 01, 2004 at 02:10:46PM -0800, William Ballard wrote:
> Given:
> 
> A - 1
> A - 2
> B - 1
> B - 2
> 
> what's the simplest command or perl script to print it as:
> 
> A (1, 2)
> B (1, 2)
> 
> or something equivalent.

Hmm, one of the zillions of ways of doing something equivalent, with the
data in file tmp/msg-data:

  $ perl -nae '{push @{$x{$F[0]}},$F[2]}END{foreach(sort keys %x){print "$_ ("; print join(", ",@{$x{$_}});print ")\n"}}' tmp/msg-data 
  A (1, 2)
  B (1, 2)

or perhaps a bit more legibly:

    #!/usr/bin/perl -w
    use strict;

    my %x;
    
    while ( <DATA> ) {
        chomp;
        my @F = split;
        push @{$x{$F[0]}}, $F[2]
        }
    
    foreach ( sort keys %x ) {
        print "$_ (";
        print join(", ",@{$x{$_}});
        print ")\n"
        }
    
    __END__
    A - 1
    A - 2
    B - 1
    B - 2

This builds a hash keyed on the first space-delimited token on a line,
with the hash value being an array reference to which the 3rd token
is pushed.  Afterwards the hash is iterated for printing, and the arrays
pretty-printed using join.

Ken

-- 
Ken Irving, Research Analyst, fnkci@uaf.edu, 907-474-6152
Water and Environmental Research Center
Institute of Northern Engineering
University of Alaska, Fairbanks