Script / sort question; sort on last field of a line?

[Alex Beamish]

A possible solution in Perl:

----------------------------------
#!/usr/bin/perl -w

#  Sort using the last word of each line.

use strict;
use warnings;

my %hash;

while(<>) {

  #  Strip any newline, split line into words.

  chomp;
  my @a=split(/ /,$_);

  #  Stuff the line into a hash of arrays, using the last word as the hash
key.

  push(@{$hash{$a[-1]}},$_);
}

#  Dump out the sorted (using the default sorting algorithim) results from
the
#  hash.

foreach my $key ( sort keys %hash ) {

  #  Within each key there may be several lines; dump them out in the order
  #  that they were encountered.

  foreach(@{$hash{$key}}) {

    print "$_\n";
  }
}

#  Done.
----------------------------------

To sort on the second to last field, change the '-1' to '-2'; you can also
subsitute your own sort algorithim after the word 'sort'. You can also
change what consitutes a 'word' by changing the delimiter in the split
statement.

--
Alex Beamish
Toronto, Ontario

On 5/4/06, Walter Dnes <waltdnes-SLHPyeZ9y/tg9hUCZPvPmw at public.gmane.org> wrote:
>
>   How do I sort on the last (or 2nd last or whatever) field of a line?
>
>   One awkward possibility involves rewriting the lines backwards,
> sorting on what is now the first field, and rewriting the lines
> backwards a second time.  I'm not aware of a utility to do write lines
> backwards.  I am *NOT* thinking of "tac" which writes the lines
> unaltered but reverses their order.  I want to write *EACH INDIVIDUAL
> LINE* backwards.  The following script does what I want...
>
> #!/bin/bash
> while read
> do
>   line_out=""
>   line_pointer=$(( ${#REPLY} - 1 ))
>   while [[ ${line_pointer} -ge 0 ]]
>   do
>     line_out="${line_out}${REPLY:${line_pointer}:1}"
>     line_pointer=$(( ${line_pointer} - 1 ))
>   done
>   echo "${line_out}"
> done
>
> --
> Walter Dnes <waltdnes-SLHPyeZ9y/tg9hUCZPvPmw at public.gmane.org> In linux /sbin/init is Job #1
> My musings on technology and security at http://tech_sec.blog.ca
> --
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