Shell Programming and Scripting

file1.IN
file2.IN
file3.IN
file1.OUT
file2.OUT

file3.MISS

for FN in *.IN; do [ -f ${FN/IN/OUT} ] || echo ${FN/IN/MISS}; done
file3.MISS

ls -1 /path/to/files |
 awk '{arr[ substr($1, 1, index($1,".")-1 )]++;} 
          END{for (i in arr) {if (arr[i]== 1){
                print i ".MISS"
                }}}'

for file in *.IN
do
   if [[ -e ${file%%IN}OUT ]]; then
      :
   else
      echo ${file%%IN}MISS
   fi
done

for file in *.IN
do
   if [[ ! -e ${file%%IN}OUT ]]; then
      echo ${file%%IN}MISS
   fi
done