Very Computer

I know this is a very simple task.
And yes, I have used the google search on that topic, but I still dont
get it to work.

I want to check a string by a function, whether that string is a valid
domain adress, assuming, that those consist of 3 parts, which are
divided by dots. The last part may not contain numbers, the other
party may not be empty or have chars other than
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.
I tried

is_domain() {
for i in `echo $* | sed -e 's/\(.\)/\1 /g`
do
case i in [!0-9a-zA-Z]) return 1;;
esac
done
oldifs=$IFS
IFS=.
set "$*"
IFS=$oldifs
for i in `echo $3 | sed -e 's/\(.\)/\1 /g`
do
case i in [a-zA-Z]) return 1;;
esac
done

if is_domain xxx.yyy.xxx
then
...
fi

But it always returns true, even with IPs.
I suppose something with those brackets is wrong.

Quote:> I know this is a very simple task.
> And yes, I have used the google search on that topic, but I still dont
> get it to work.

> I want to check a string by a function, whether that string is a valid
> domain adress, assuming, that those consist of 3 parts, which are
> divided by dots. The last part may not contain numbers, the other
> party may not be empty or have chars other than
> abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.

[...]

Note that it is not the way we usually define a domain name.
Anyway, what about:

is_domain() {
  (
    IFS=.
    set -- $1
    [ $# -eq 3 ] || return 1
    case $1 in
      ""|*[!a-zA-Z0-9-]*|[0-9-]*|*-) return 1;;
    esac
    case $2 in
      ""|*[!a-zA-Z0-9-]*|[0-9-]*|*-) return 1;;
    esac
    case $3 in
      ""|*[!a-zA-Z]*) return 1;;
    esac
  )

Quote:}

--
Stphane

 > I know this is a very simple task.
 > And yes, I have used the google search on that topic, but I still dont
 > get it to work.
 >
 > I want to check a string by a function, whether that string is a valid
 > domain adress, assuming, that those consist of 3 parts, which are
 > divided by dots. The last part may not contain numbers, the other
 > party may not be empty or have chars other than
 > abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.

[ . . . ]

It's not clear to me what you're requiring of the 3d part.  I think you
want the last part to be just alpha characters.

In the korn shell (and in bash, if you do `shopt -s extglob'), you can do,

function isdomain {
     case $1 in
     +([[:alnum:]]).+([[:alnum:]]).+([[:alpha:]])) return 0;;
     *) return 1;;
     esac

Quote:}

If you want what you've asked for, namely the last part to be anything,
even null, as long as it doesn't contain a *digit* or a *.*, then

function isdomain {
     case  $1 in

     *) return 1;
     esac

Quote:}

--
Regards,

---Robert

Of course I wanted the 3rd part not to be anything, but only letters.
Just a typo with return 1 and return 0.
Is it possible to have that [] check in an if clause?
I tried it, but just messed up my script.

[ . . . ]

Talk about typos, the line above should be

Quote:> >     *) return 1;
> >     esac
> >}

> Of course I wanted the 3rd part not to be anything, but only letters.
> Just a typo with return 1 and return 0.
> Is it possible to have that [] check in an if clause?
> I tried it, but just messed up my script.

Do you mean something like this?

function isdomain {
     if [[ $1 = +([[:alnum:]]).+([[:alnum:]]).+([[:alpha:]]) ]]
     then
         return 0
     else
         return 1
     fi

Quote:}

But why does it have to be an *if* statement?

--
Regards,

---Robert

[...]

Quote:> Do you mean something like this?

> function isdomain {
>      if [[ $1 = +([[:alnum:]]).+([[:alnum:]]).+([[:alpha:]]) ]]
>      then
>          return 0
>      else
>          return 1
>      fi
> }

> But why does it have to be an *if* statement?

Yes,

function isdomain {
     [[ $1 = +([[:alnum:]]).+([[:alnum:]]).+([[:alpha:]]) ]]

Quote:}

Should be enough. However note that a domain part normally can't
start with a digit and should only contain ASCII chars (be
carefull to the locale variants for [:al***:])

$ env -i LANG=C ksh -c '[[ = [[:alpha:]] ]]' && echo yes

yes

--
Stphane

I wish that were true... see www.3com.com for an example (I believe
they lobbied quite hard to ensure this was valid).
Adam

[...]

Quote:>> However note that a domain part normally can't
>> start with a digit
> I wish that were true... see www.3com.com for an example (I believe
> they lobbied quite hard to ensure this was valid).
> Adam

Yes, RFC 1035 only gives recommandations on the name of domains:

-|The following syntax will result in fewer problems with many
-|applications that use domain names (e.g., mail, TELNET).
-|
-|<domain> ::= <subdomain> | " "
-|
-|<subdomain> ::= <label> | <subdomain> "." <label>
-|
-|<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]
-|
-|<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
-|
-|<let-dig-hyp> ::= <let-dig> | "-"
-|
-|<let-dig> ::= <letter> | <digit>
-|
-|<letter> ::= any one of the 52 alphabetic characters A through Z in
-|upper case and a through z in lower case
-|
-|<digit> ::= any one of the ten digits 0 through 9

So, to check a domain name against that recommandation, we could write:

is_domain() {
  (
    IFS=.
    for i in $1; do
      case $i in
        ""|*[!a-zA-Z0-9-]*|[!a-zA-Z]*|*-) return 1;;
      esac
    done
  )

Quote:}

--
Stphane