INSTR function

Purpose	Search a string for the existence of a second string.
Syntax	y& = INSTR([Position&,] Main$, [ANY] Match$)
Remarks	INSTR returns the position of Match$ within Main$. The return value is indexed to one, while zero means "not found". Position& specifies the character position to begin the search. If Position& is one or greater, Main$ is searched left to right. The value one starts at the first character, two the second, etc. If Position& is -1 or less, Main$ is searched from right to left. The value -1 starts at the last character, -2 the second to last, etc. If Position& is not given, the default value of +1 is assumed. x& = INSTR("xyz", "y") ' returns 2 x& = INSTR("xyz", "a") ' returns 0 a$ = "My Dog" : b$ = " " x& = INSTR(a$, b$) ' returns 3 It is important to note that in all cases, even when Position& is negative, the return value of INSTR() is the absolute position of the match, from left to right, starting with the first character.
ANY	If the ANY keyword is included, Match$ specifies a list of single characters. INSTR searches for each of these characters individually. As soon as any one of these characters is found, INSTR returns the position of the match. x& = INSTR(-2, "efcdef", ANY "ef") returns a result of 5 INSTR is case-sensitive, meaning that upper-case and lower-case letters must match exactly in Match$ and Main$.
Restrictions	Special search terms are evaluated in this sequence: If Position& is zero, or beyond the length of Main$, the value zero is returned. If Main$ is null, the value zero is returned. If Match$ is null, the absolute Position& value (default of 1) is returned.
See also	EXTRACT$, LCASE$, LEFT$, LTRIM$, MID$, RIGHT$, RTRIM$, SHRINK$, TALLY, TRIM$, UCASE$, VERIFY
Example	' x$ = first command-line argument, assuming spaces, commas, ' periods, and tabs are valid delimiters. IF INSTR(COMMAND$, ANY " ,." + CHR$(9)) > 0 THEN x$ = "There is more than one command-line argument" ELSE x$ = "There is at most one command-line argument" END IF