1 (edited by Stefan 2007-04-22 01:19:33)

Topic: Extract only the end of a string

Extract only the end of a string




   From:
   A0B1C2DE_0201.jpg
   A1B#0302.gif

   To:
   0201.jpg
   0302.gif

   Use the expression:
   %f(-8)





How does it work ?
   The "()" modifier permits the extraction of a part of the string it is associated to.
     Its first parameter is the starting position of this extraction,
     an optional second parameter specifies the number of characters to extract. [e.g. %f(1,4)]
     If it's not given, the extraction is done until the end.


Which value to choose as starting position ?
   It depends on the file we examine.

     10 would be the starting position for the first

   1234567890
   A0B1C2DE_0
201.jpg
   
   
     and 5 would be the starting position for the second ...

   12345
   A1B#0
302.gif


In fact, we only need the last 8 characters.
     If Siren could provide us such an feature that would help us a lot!

    
It would be interesting to specify
     that the number of the first character to extract
     is relative to the end and not the beginning of the string.
    
     Siren manages this with "negative" numbers.
   For example, with "ABCDEF":
   %b(2,1)  gives "B" : positive start, so relative to the beginning
   %b(-2,1) gives "E" : negative start, so relative to the end

   More clearly, -8 "alone" will specify: "the 8 last characters"


Let's test this:
   %f is the full file name

   So, following the expression for "A1B#0302.gif":
   %f     gives "A1B#0302.gif"
   %f(-8) gives "0302.gif"

   And for A0B1C2DE_0201.jpg
   %f     gives   "A0B1C2DE_0201.jpg"
   %f(-8) gives   "0201.jpg"


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