# Checking number of command line args

case $# in
0)  echo "You forgot to supply the argument" ;;
1)   ... process the argument ...  ;;
*)  echo "You supplied too many arguments" ;;
esac

# Classifying a file via its name

case "$file" in
*.c)  echo "$file looks like a C source-code file" ;;
*.h)  echo "$file looks like a C header file" ;;
*.o)  echo "$file looks like a an object file" ;;
...
?)    echo "$file's name is too short to classify it" ;;
*)    echo "I have no idea what $file is" ;;
esac