Use the string library string:chr and string:rchr functions. string:chr searches a string for a character (starting from the left hand side of the string), and returns its index. string;rchr performs the same task, starting from the right hand side. Note that all Erlang indexes are 1-based:
1> string:chr("Hello, World!", $,).
6
2> string:chr("My, this is a lot of commas, I guess.", $,).
3
3> string:rchr("My, this is a lot of commas, I guess.", $,).
28
string:chr and string:rchr return 0 if no match is found:
4> string:chr("This sentence has no commas.", $,).
0
5> string:rchr("This sentence has no commas.", $,).
0
