Shell Programming and Scripting

printf "Enter column name: "
read col

awk -v C="$col" '
        NR == 1 {
                        for ( i = 1; i <= NF; i++ )
                        {
                                if ( $i == C )
                                        break;
                        }
        }
        NR > 1 {
                        A[$i]
        }
        END {
                for ( k in A )
                        print k
} ' file

$ ./krish
Enter column name: Column1
a
b
c

awk 'NR==1 {for(i=1; $i!=C; i++) if(i>NF) exit; next} {print $i}' C=Column3 file

awk     'NR == 1        {for (i = 1; i <= NF; i++ ) if ( $i == C ) break }
         LL[$i]         {next}
                        {print $i; LL[$i]++}
        ' C="$col" file
Column1
a
b
c

awk -v COL="$var" 'NR==1 {for(i=1;i<=NF;i++){if($i==COL){break;}}}
		NR>1 && !A[$i]++ {print $i}' file