Check IP adrress with regular expression

Hi all,

I try to use regular expression to check the pattern of IP address, I tried with

IP = regexp(str, '[0-255]\.[0-255]\.[0-255]\.[0-255]', 'match')

but i can't work.

So, anyone know how to set the digit that range is from 0 to 255 to check the pattern of IP address? I tried with

    IP = regexp(str, '[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?', 'match')

but it doesn't work for every situation.

Your suggestion and help is much appreciated. Thank you.

Answer 1

[Walter Roberson]

0*

to allow leading 0's.

After that you can have

1\d\d

or

2[0-4]\d

or

25[0-4]

or

\d\d

or

\d

so take all those possibilities and join them with |

 0*(1\d\d|2[0-4]\d|25[0-4]|\d\d|\d)

If you call that (say) Q, then your fuller pattern becomes

((Q\.){3}Q)

Then if necessary you would put guards around it to ensure that it was not proceeded or followed by a digit or a period