Shell Programming and Scripting

Column A Column B
Apples      1900
Apples      1901
Pears        1902
Pears        1903

Column A Column B Column C
Apples          2              1900
Apples          2              1901
Pears            2              1902
Pears            2              1903

awk 'NR == FNR {T[$1]++; next} FNR == 1 {print $1, $2, "CNT", $3, $4; next} {print $1, T[$1], $2}' file file
Column A CNT Column B
Apples 2 1900
Apples 2 1901
Pears 2 1902
Pears 2 1903

awk 'NR == FNR {T[$1]++; next} FNR > 1{print $1, T[$1], $2}' pshields1984.input  pshields1984.input

NR == FNR {T[$1]++; next} # execute only in the first pass reading input
FNR > 1{print $1, T[$1], $2}  # skip first line and insert the tally in from previous read after the first column

#!/usr/bin/perl

use strict;
use warnings;

my $filename = shift or die "Usage: $0 FILENAME\n";
my %tally;

open my $fh, '<', $filename or die "Could not open $filename: $!\n";

<$fh>;
my $data_position = tell $fh;

while (my $entry = <$fh>) {
    my ($id) = split '\s+', $entry;
    $tally{$id}++;
}
seek $fh, $data_position, 0;
while (my $entry = <$fh>) {
    my @fields = split '\s+', $entry;
    splice @fields, 1,0, $tally{$fields[0]};
    print "@fields\n";
}
close $fh;