To remove the first character in a string:
echo $STRING |sed ‘s/.\(.*\)/\1/’

To remove the last character in a string:
echo $STRING | sed ‘s/\(.*\)./\1/’

To remove the last five characters in a string:
echo $STRING | sed ‘s/\(.*\)…../\1/’

To remove all whitespace at the end of the line:
echo $STRING | sed ‘s/[ ]*$//’