Shell Programming and Scripting

A123|Peter|20
A123|Jack |10
B222|Helen|15
B222|Jane |13
B222|Guy  |30

#!/bin/sh

while read line; do
  c1=$(echo "$line" | cut -d\| -f1)
  c3=$(echo "$line" | cut -d\| -f3)
  [ ! "$p1" ] && p1="$c1"
  [ ! "$min" ] && min="$c3"  
  if [ "$c1" = "$p1" ]; then
    if [ "$c3" -lt "$min" ]; then
      min="$c3"; line1="$line"
    fi
  else
    p1="$c1"; min="$c3"
    echo "$line1"    
  fi
done < file
echo "$line1"

awk -F"|" '$1 in min {if($3 < min[$1]){min[$1]=$3;s[$1]=$2};next}
{min[$1]=$3;s[$1]=$2}
END{for(i in min)print i FS s[i] FS min[i]}
' file

$ 
$ cat data.txt
A123|Peter|20
A123|Jack |10
B222|Helen|15
B222|Jane |13
B222|Guy  |30
C333|Ana  |40
C333|Abe  |70
D444|Ben  |50
$ 
$ perl -ne 'chomp; ($a,$b,$c)=split/\|/; $b=~s/\s+$//;
          if ($a ne $pa) {push @y,"$a|$b|$c\n"}
          elsif ($c<$pc) {$y[$#y]="$a|$b|$c\n"}
          $pa=$a; $pc=$c;
          END {print @y}' data.txt
A123|Jack|10
B222|Jane|13
C333|Ana|40
D444|Ben|50
$ 
$

#!/usr/bin/env bash

# @(#) s1	Demonstrate re-ordering for minimum in specific field.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) sort uniq
set -o nounset
echo

FILE=${1-data1}

echo " Data file $FILE:"
cat $FILE

echo
echo " Results:"
sort -t'|' --key=1,1 --key=3,3n $FILE |
uniq -w4

exit 0

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
GNU bash 3.2.39
sort (GNU coreutils) 6.10
uniq (GNU coreutils) 6.10

 Data file data1:
A123|Peter|20
B222|Helen|15
A123|Jack |10
B222|Jane |13
B222|Guy  |30

 Results:
A123|Jack |10
B222|Jane |13

#!/usr/bin/perl

# @(#) p1	Demonstrate finding minimum value of field, single pass.

use warnings;
use strict;

my ($debug);
$debug = 1;
$debug = 0;
my ( $current, %hash, $id, $grade );

# Read file, make hash entry if new or lower value.

while (<>) {
  chomp;
  ( $id, $grade ) = ( split(/[|]/) )[ 0, 2 ];
  print " id, grade = :$id:, :$grade:\n" if $debug;
  if ( exists $hash{$id} ) {
    $current = ( split( /[|]/, $hash{$id} ) )[2];
    if ( $current < $grade ) {
      next;
    }
  }
  $hash{$id} = $_;
}

# Sort keys and print values from the hash.

for $id ( sort keys %hash ) {
  print "$hash{$id}\n";
}

print STDERR " ( Lines read: $. )\n" if $debug;

exit(0);

% ./p1 data1
A123|Jack |10
B222|Jane |13