Think of a problem finding the substring def in the string abcdefg.
I though Fortran does not have an efficient way of doing this and I have
to make own subroutine to achieve this. But Fortran has such a function,
index.
See, INDEX — position of a substring within a string
Its syntax is, :
RESULT = INDEX(STRING, SUBSTRING [, BACK [, KIND]])
and the return value is an integer of the substring position.
The return value starts from 1 if the substring exists. If there is nothing matched with the substring, the return value becomes 0.