src="/path/to/foo.cpp"
base=${src##*/}   #=> "foo.cpp" (basepath)
dir=${src%$base}  #=> "/path/to/" (dirpath)

str="/path/to/foo.cpp"
echo "$str"           # /path/to/foo (variable expansion)
echo "${str}"         # /path/to/foo (variable expansion)
echo '$str'           # '$str' (disabled variable expansion)
echo "${str%.cpp}"    # /path/to/foo
echo "${str%.cpp}.o"  # /path/to/foo.o
echo "${str%/*}"      # /path/to

echo "${str##*.}"     # cpp (extension)
echo "${str##*/}"     # foo.cpp (basepath)

echo "${str#*/}"      # path/to/foo.cpp
echo "${str##*/}"     # foo.cpp

echo "${str/foo/bar}" # /path/to/bar.cpp

dir=${0%/*}

file="Some/path/to/file.txt"
echo "Extension: ${file##*.}"
echo "Name sans extension: ${file%.*}"
echo "New extension: ${file%txt}gif"