Go to standardXPath function: string substring (string, number, number?)
Standard excerpt:
The substring function returns the substring of the first argument starting at the position specified in the second argument
with length specified in the third argument. For example, substring("12345",2,3) returns "234". If the third argument is not
specified, it returns the substring starting at the position specified in the second argument and continuing to the end of
the string. For example, substring("12345",2) returns "2345".
Examples (xslt:xml): Overview
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Interactive xlab: [string functions] [xpath] [xsl:value-of] [xsl:template]