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The _INSTRREV function searches for a substring inside another string, but unlike INSTR it searches from right to left.


position% = _INSTRREV([start%,] baseString$, subString$)


  • The optional literal or variable INTEGER start% indicates where in the baseString$ the search must start, counted from the left.
  • The baseString$ is a literal or variable STRING value to be searched for an exact match including letter cases.
  • The subString$ is a literal or variable STRING value being searched.


  • The function returns the position% in the baseString$ where the subString$ was found, from right to left.
  • position% will be 0 if the search found no matches in the base string.
  • _INSTRREV returns 0 if an empty baseString$ is passed, and returns LEN(baseString$) with an empty subString$.
  • The start% position is useful when making multiple searches in the same string. See the example below.
  • The subString$ should be smaller or equal in length to the baseString$, or 0 is returned.
  • A start% value of 0 or less starts search from the end of the baseString$ (same as not passing a start% parameter).


Example 1: Separating a file name from a full path.

fullPath$ = "C:\Documents and Settings\Administrator\Desktop\qb64\internal\c\libqb\os\win\libqb_1_2_000000000000.o" file$ = MID$(fullPath$, _INSTRREV(fullPath$, "\") + 1) PRINT file$


Example 2: Searching for multiple instances of a substring inside a base string, going from the end to the start.

sentence$ = " This is a string full of spaces, including at start and end... " PRINT sentence$ DO findPrevSpace% = _INSTRREV(findPrevSpace% - 1, sentence$, SPACE$(1)) IF findPrevSpace% = 0 THEN LOCATE 4, 1 PRINT "No more spaces" EXIT DO END IF LOCATE 2, findPrevSpace% PRINT "^" totalSpaces = totalSpaces + 1 IF findPrevSpace% = 1 THEN LOCATE 4, 1 PRINT "Last space found at position 1" EXIT DO END IF LOOP PRINT "Total spaces found: "; totalSpaces

This is a string full of spaces, including at start and end... ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Last space found at position 1 Total spaces found: 13

See also

Keyword Reference - Alphabetical
Keyword Reference - By Usage
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