Comparing file names with different extensions

Shell Programming and Scripting
1

Hello, I need some help. I have files in one and the same directory, but with different extensions, like this:

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

Apparently some files with OUT extension can be missing. So I want to compare *.IN and *.OUT, ignoring the extension and get result like:
Missing OUT files:

file3.MISS

Thanks!

2

Not too clear a specification... Howsoever, try

for FN in *.IN; do [ -f ${FN/IN/OUT} ] || echo ${FN/IN/MISS}; done
file3.MISS
3 
ls -1 /path/to/files |
 awk '{arr[ substr($1, 1, index($1,".")-1 )]++;} 
          END{for (i in arr) {if (arr== 1){
                print i ".MISS"
                }}}'
4 
for file in *.IN
do
   if [[ -e ${file%%IN}OUT ]]; then
      :
   else
      echo ${file%%IN}MISS
   fi
done

---------- Post updated at 11:36 ---------- Previous update was at 11:23 ----------

... or make it quicker/simpler with:

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

(I wrote the first example on the fly;) )