#include <StringConstants.au3> ; to declare the Constants of StringRegExp
#include <Array.au3> ; UDF needed for _ArrayDisplay and _ArrayConcatenate
Local $sRegex = "\s*[Cc]:(?:(?:\/|\\{1,2})\w+)+\.\w+"
Local $sString = "C:\Users\esteban\Desktop\Java_file_testing\file3.txt" & @CRLF & _
"C:/Users/esteban/Desktop/Java_file_testing/file3.txt" & @CRLF & _
"C://Users//esteban//Desktop//Java_file_testing//file3.txt" & @CRLF & _
"c:\\Users\\esteban\\Desktop\\Java_file_testing\\file3.txt" & @CRLF & _
"" & @CRLF & _
""
Local $aArray = StringRegExp($sString, $sRegex, $STR_REGEXPARRAYGLOBALFULLMATCH)
Local $aFullArray[0]
For $i = 0 To UBound($aArray) -1
_ArrayConcatenate($aFullArray, $aArray[$i])
Next
$aArray = $aFullArray
; Present the entire match result
_ArrayDisplay($aArray, "Result")
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm