Hello, @james-norton, @alan-kilborn, @terry-r and All,
BTW, note that there’s an important difference between :
To search for IPV4 addresses, in a file containing valid IVP4 addresses, only
To search for valid IPV4 addresses, in a file which may contain some non valid IPV4 addresses !
In the first case, as the @terry-r’s solution, simply use the almost obvious regex \b(\d{1,3}\.){3}\d{1,3}\b
In the second cas, use one of the two regexes, below :
(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(*FAIL)|\b((?1)\.){3}(?1)\b
(?(DEFINE)(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d))\b((?1)\.){3}(?1)\b
Notes :
In the first regex, once the part (25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d) is stored as group 1, the (*FAIL) control verb discards this match but this regex part can be re-used with the syntax (?1). Then, the second alternative \b((?1)\.){3}(?1)\b does match a valid IPV4 address !
The second regex uses a special conditional syntax with the key expression (DEFINE). which stores, as above, the part 25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d, between parentheses, but which is never matched, by definition. So the effective regex is just the part \b((?1)\.){3}(?1)\b, coming next, which match valid IPV4 addresses only
Best Regards,
guy038
