when I even I put this command I get this result

. gen has_x= strpos (ICD , "X") >0
strpos not found
r(111);



Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int(DOB Dateofstudy) str4 GENDER byte AGE str4 ICD
-3538 19715 "Male" 63 "10X" 
-5492 19711 "Male" 69 "13X" 
-2395 19722 "Male" 60 "53N" 
-4061 19712 "Male" 65 "33NX"
-3676 19719 "Male" 64 "22G" 
-3408 19719 "Male" 63 "27J" 
-4884 19712 "Male" 67 "114s"
-5500 19719 "Male" 69 "221" 
-3542 19718 "Male" 63 "21x" 
-3748 19722 "Male" 64 "225x"
end
format %tdnn/dd/CCYY DOB
format %tdnn/dd/CCYY Dateofstudy
any help or advice? thank you