6.1.2.11.1.14 InStr / InStrB

Function Declaration

 Function InStr(Optional Arg1 As Variant, Optional Arg2 As 
 Variant, Optional Arg3 As Variant, Optional Compare As 
 VbCompareMethod = vbBinaryCompare) 

If Arg3 is not present then Arg1 is used as the string to be searched, and Arg2 is used as the pattern (and the start position is 1). If Arg3 IS present then Arg1 is used as a string and Arg2 is used as the pattern.

Parameter	Description
Arg1	Numeric expression that sets the starting position for each search. If omitted, search begins at the first character position. If start contains the data value Null, an error occurs. This argument is required if Compare is specified.
Arg2	String expression to search.
Arg3	String expression sought.
Compare	Specifies the type of string comparison. If compare is the data value Null, an error occurs. If Compare is omitted, the Option Compare setting determines the type of comparison. Specify a valid LCID (LocaleID) to use locale-specific rules in the comparison.

Runtime Semantics.

§ Returns a Long specifying the position of the first occurrence of one string within another.

§ The Compare argument can have the following values (if omitted, it uses the <option-compare-directive> of the calling module):

Constant	Value	Description
vbBinaryCompare	0	Performs a binary comparison.
vbTextCompare	1	Performs a textual comparison.

§ InStr returns the following values:

If	InStr returns
Arg2 is zero-length	0
Arg2 is Null	Null
Arg3 is zero-length	Arg1
Arg3 is Null	Null
Arg3 is not found	0
Arg3 is found within Arg2	Position at which match is found
Arg1 > Arg3	0

§ The InStrB function is used with byte data contained in a string. Instead of returning the character position of the first occurrence of one string within another, InStrB returns the byte position.