substring(string, start)
substring(string, start, length)

string

The string to evaluate.

start

The position within string the substring begins

length Optional

The length of the substring. If omitted, the returned string will contain every character from the start position to the end of string.

A string.

As in other XPath functions, the position is not zero-based. The first character in the string has a position of 1, not 0.

XPath 1.0 4.2

Supported.