How to check if an argument has a single character in shell

Question

I'm trying to make a script to check if an argument has a single uppercase or lowecase letter, or if its anything else (a digit or a word for example.)

So far got this done:

if echo $1 | egrep -q '[A-Z]';
    then echo "Uppercase";
elif echo $1 | egrep -q '[a-z]';
    then echo "Lowercase";
else
    echo "FAIL";
fi 

Need to make it to fail me not only if it isnt a letter, but if I insert a word or 2 letters.

Answer 1

You was very close !

if echo $1 | egrep -q '^[A-Z]$';
    then echo "Uppercase";
elif echo $1 | egrep -q '^[a-z]$';
    then echo "Lowercase";
else
    echo "FAIL";
fi

• I've just added the special characters ^ & $, means respectively start of line & end of line
• no need egrep there, grep is sufficient