XSL substring and indexOf

Here is some one liner xpath 1.0 expressions for IndexOf( $text, $searchString ):

If you need the position of the FIRST character of the sought string, or 0 if it is not present:

contains($text,$searchString)*(1 + string-length(substring-before($text,$searchString)))

If you need the position of the first character AFTER the found string, or 0 if it is not present:

contains($text,$searchString)*(1 + string-length(substring-before($text,$searchString)) + string-length($searchString))

Alternatively if you need the position of the first character AFTER the found string, or length+1 if it is not present:

1 + string-length($right) - string-length(substring-after($right,$searchString))

That should cover most cases that you need.

Note: The multiplication by contains( ... ) causes the true or false result of the contains( ... ) function to be converted to 1 or 0, which elegantly provides the "0 when not found" part of the logic.

It's not clear exactly what you want to do with the index of a substring [update: it is clearer now - thanks] but you may be able to use the function substring-after or substring-before:

substring-before('My name is Fred', 'Fred')

returns 'My name is '.

If you need more detailed control, the substring() function can take two or three arguments: string, starting-index, length. Omit length to get the whole rest of the string.

There is no index-of() function for strings in XPath (only for sequences, in XPath 2.0). You can use string-length(substring-before($string, $substring))+1 if you specifically need the position.

There is also contains($string, $substring). These are all documented here. In XPath 2.0 you can use regular expression matching.

(XSLT mostly uses XPath for selecting nodes and processing values, so this is actually more of an XPath question. I tagged it thus.)

I want to select the text of a string that is located after the occurrence of substring

You could use:

substring-after($string,$match)

If you want a subtring of the above with some length then use:

substring(substring-after($string,$match),1,$length)

But problems begin if there is no ocurrence of the matching substring... So, if you want a substring with specific length located after the occurrence of a substring, or from the whole string if there is no match, you could use:

substring(substring-after($string,substring-before($string,$match)),
          string-length($match) * contains($string,$match) + 1,
          $length)