Function: indexOf()

Returns the character position of one string inside another.

...

indexOf("Thomas Troubridge", "x")

Returns 0.

do( 
   $start = indexOf(in.fileName, "_") + 1, 
   $end = $start + 8, 
   $date = substring(in.fileName, $start, $end)
)

If in.fileName contained file names like "switchRC48_20060708.exp", the script above would extract the date element of the file name.

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