Shell Programming and Scripting

Input

m1,s1,x1,x1
m1,s2,x2,x2
m1,s3,x2,x2
m1,s4,x1,x1
m1,s5,x1,x2
m2,s1,y2,y2
m2,s2,y1,y1
m2,s3,y2,y1
m2,s4,y2,y1
m2,s5,y1,y1
m3,s1,y2,y2
m3,s2,y2,y2
m3,s3,y2,y1
m3,s4,y2,y1
m3,s5,y1,y1

Output

m1,s1,a
m1,s2,b
m1,s3,b
m1,s4,a
m1,s5,c
m2,s1,a
m2,s2,b
m2,s3,c
m2,s4,c
m2,s5,b

awk -F, '
{
   if(!($1 in m)) {
      m[$1]++
      s[$1]=$2
      v[$1,1]=$3 FS $4
      next
   }
   if(m[$1]==1) {
      m[$1]++
      if(v[$1,1] == $3 FS $4) v[$1,1]=""
      else {
         print $1, s[$1], "a"
         v[$1,2]=$3 FS $4
      }
   }
   if(!v[$1,1]) next

   for(i=1;i<=m[$1];i++)
       if(v[$1,i] == $3 FS $4) {
           printf "%s%c\n", $1 FS $2 FS, 96 + i
           next
        }
   v[$1,++m[$1]]=$3 FS $4
   printf "%s%c\n", $1 FS $2 FS, 96 + m[$1]
}' OFS=, infile