Shell Programming and Scripting

awk '{ x[$1]=x[$1] " " $2; y[$2]=y[$2] " " $1; } 
END { 
   for (k in x) print k,x[k] >"OUTPUT1";  
   for (k in y) print k,y[k] >"OUTPUT2"; 
}' INPUT

awk '
{ 
   x[$1]=x[$1] " " $2;   # Append 2nd field to contents of x[$1] (followed by a space)
   y[$2]=y[$2] " " $1;  # Append 1st field to contents of y[$1] (followed by a space)
} 
# Now: The array "x" contains all the lines keyed by the first field. 
#         The array "y" contains all the lines keyed by the second field.

END { 
   for (k in x) print k,x[k] >"OUTPUT1";  
   for (k in y) print k,y[k] >"OUTPUT2"; 
}' INPUT

awk '{
arr[$1]=sprintf("%s %s",arr[$1],$2)
brr[$2]=sprintf("%s %s",brr[$2],$1)
}
END{
for(i in arr)
        print i""arr[i]
print "-------------------"
for(j in brr)
        print j""brr[j]
}' filename