Finding @ in a string, and other items

**Chung Leong** · Jul 17 '05, 03:03 AM

Re: Finding @ in a string, and other items

It's easiest to use regexp to deal with this sort of thing.
preg_match('/^[\w\.]+@\w+\.\w+/', $address) should do the trick.

Uzytkownik "Picture Dots" <webmaster@brim stonedragons.co m> napisal w
wiadomosci news:HQXVb.9637 $se3.4553@fe1.c olumbus.rr.com. ..[color=blue]
> Ok - I want to check a string for @ in it (Im checking to see if a string
> that should contain an email holds a @ )
>
> How would I go about this? preg_match? ereg? strstr?Examples ?
>
> Also - how would I find any non alpha numeric characters in a string so I
> can give the user an error message. I dont want any characters besides
> alpha-numeric in the strings.
>
>[/color]

**Geoff Berrow** · Jul 17 '05, 03:15 AM

Re: Finding @ in a string, and other items

I noticed that Message-ID: <woGdnXBYuMT89r XdRVn-ug@comcast.com> from
Chung Leong contained the following:
[color=blue]
>It's easiest to use regexp to deal with this sort of thing.
>preg_match('/^[\w\.]+@\w+\.\w+/', $address) should do the trick.[/color]

Reg exp and easy in the same sentence?

if (!strpos($email ,"@"))
{
print "try again, email addresses must contain \"@\"";
}
else{
print "That's a fine email address!";
}

--
Geoff Berrow (put thecat out to email)
It's only Usenet, no one dies.
My opinions, not the committee's, mine.
Simple RFDs http://www.ckdog.co.uk/rfdmaker/

**Michel** · Jul 17 '05, 03:15 AM

Re: Finding @ in a string, and other items

Your solution does not provide any check other than checking for existance
of @
The regexp does :)

Mich

"Geoff Berrow" <blthecat@ckdog .co.uk> wrote in message
news:gi7h20tg2l k9v4g433f1tgc4q mnm9d45cf@4ax.c om...[color=blue]
> I noticed that Message-ID: <woGdnXBYuMT89r XdRVn-ug@comcast.com> from
> Chung Leong contained the following:
>[color=green]
> >It's easiest to use regexp to deal with this sort of thing.
> >preg_match('/^[\w\.]+@\w+\.\w+/', $address) should do the trick.[/color]
>
> Reg exp and easy in the same sentence?
>
> if (!strpos($email ,"@"))
> {
> print "try again, email addresses must contain \"@\"";
> }
> else{
> print "That's a fine email address!";
> }
>
> --
> Geoff Berrow (put thecat out to email)
> It's only Usenet, no one dies.
> My opinions, not the committee's, mine.
> Simple RFDs http://www.ckdog.co.uk/rfdmaker/[/color]

**John Dunlop** · Jul 17 '05, 03:15 AM

Re: Finding @ in a string, and other items

Michel wrote upsidedown:
[color=blue]
> "Geoff Berrow" <blthecat@ckdog .co.uk> wrote in message
> news:gi7h20tg2l k9v4g433f1tgc4q mnm9d45cf@4ax.c om...
>[color=green]
> > if (!strpos($email ,"@")) [...][/color]
>
> Your solution does not provide any check other than checking for existance
> of @[/color]

One of the queries was how to go about checking a string contained
"@". Using regular expression functions for that alone would be
inefficient.
[color=blue]
> The regexp does :)[/color]

Indeed. But it doesn't answer the other query (how to detect non-
alphanumeric characters in a string). So why use it?

I suspect Picture Dots is trying to confirm the validity of email
addresses, but neither the Subject line nor the body of the original
article says so. The pattern in question is insufficient for
checking email address syntax.

--
Jock

**Geoff Berrow** · Jul 17 '05, 03:15 AM

Re: Finding @ in a string, and other items

I noticed that Message-ID: <c0ajk1$ac$1@ne ws.cistron.nl> from Michel
contained the following:
[color=blue]
>Your solution does not provide any check other than checking for existance
>of @
>The regexp does :)[/color]

I know. But I think such checks are pointless anyway.
--
Geoff Berrow (put thecat out to email)
It's only Usenet, no one dies.
My opinions, not the committee's, mine.
Simple RFDs http://www.ckdog.co.uk/rfdmaker/

**Chung Leong** · Jul 17 '05, 03:17 AM

Re: Finding @ in a string, and other items

More or less. Mistyping a email address that's synatically correct is far
more likely than enter a invalid character. Doing a MX lookup might be more
worthwhile than trying to write a regexp that validates RFC822 conformance.

Uzytkownik "Geoff Berrow" <blthecat@ckdog .co.uk> napisal w wiadomosci
news:bkmh20pd2c mdlra2hsdaglate uiaajdfpg@4ax.c om...[color=blue]
> I noticed that Message-ID: <c0ajk1$ac$1@ne ws.cistron.nl> from Michel
> contained the following:
>[color=green]
> >Your solution does not provide any check other than checking for[/color][/color]
existance[color=blue][color=green]
> >of @
> >The regexp does :)[/color]
>
> I know. But I think such checks are pointless anyway.
> --
> Geoff Berrow (put thecat out to email)
> It's only Usenet, no one dies.
> My opinions, not the committee's, mine.
> Simple RFDs http://www.ckdog.co.uk/rfdmaker/[/color]

**Rahul Anand** · Jul 17 '05, 03:18 AM

Re: Finding @ in a string, and other items

"Chung Leong" <chernyshevsky@ hotmail.com> wrote in message news:<hsKdndUVw 6CMX7fdRVn-jQ@comcast.com> ...[color=blue]
> More or less. Mistyping a email address that's synatically correct is far
> more likely than enter a invalid character. Doing a MX lookup might be more
> worthwhile than trying to write a regexp that validates RFC822 conformance.
>
> Uzytkownik "Geoff Berrow" <blthecat@ckdog .co.uk> napisal w wiadomosci
> news:bkmh20pd2c mdlra2hsdaglate uiaajdfpg@4ax.c om...[color=green]
> > I noticed that Message-ID: <c0ajk1$ac$1@ne ws.cistron.nl> from Michel
> > contained the following:
> >[color=darkred]
> > >Your solution does not provide any check other than checking for[/color][/color]
> existance[color=green][color=darkred]
> > >of @
> > >The regexp does :)[/color]
> >
> > I know. But I think such checks are pointless anyway.
> > --
> > Geoff Berrow (put thecat out to email)
> > It's only Usenet, no one dies.
> > My opinions, not the committee's, mine.
> > Simple RFDs http://www.ckdog.co.uk/rfdmaker/[/color][/color]

You can find a regular expression to validate email-address here:

Mail::RFC822::Address

http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html

Try using this if it worth using for your email-validation :)

--
Thanks,
Rahul Anand

**John Dunlop** · Jul 17 '05, 03:18 AM

Re: Finding @ in a string, and other items

Rahul Anand wrote:
[color=blue]
> You can find a regular expression to validate email-address here:
>
> http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html[/color]

This is a Perl module which validates email addresses against the
syntax of RFC822 (obsoleted by RFC2822); the pattern itself will not
match all valid email addresses, despite its complexity.
[color=blue]
> Try using this if it worth using for your email-validation :)[/color]

Validating the syntax of an email address and finding it exists is
not proof of it being in use. If you'd like to know that what a user
entered is really her email address, then a confirmation mail is the
best way, as both the CGI FAQ and the Mail::RFC822::A ddress
documentation recommend.

--
Jock

**Rahul Anand** · Jul 17 '05, 03:20 AM

Re: Finding @ in a string, and other items

John Dunlop <john+usenet@jo hndunlop.info> wrote in message news:<MPG.1a95c 2465fa6d64a9896 8d@News.Individ ual.NET>...[color=blue]
> Validating the syntax of an email address and finding it exists is
> not proof of it being in use. If you'd like to know that what a user
> entered is really her email address, then a confirmation mail is the
> best way, as both the CGI FAQ and the Mail::RFC822::A ddress
> documentation recommend.[/color]

Yes, I agree. Best way is to send a mail with confirmation URL or some
confirmation code. Only after actual validation you can be sure that
the request is authentic.

--
Cheers,
Rahul Anand

**Chung Leong** · Jul 17 '05, 03:21 AM

Re: Finding @ in a string, and other items

I just thought of a reason to validate the syntax of a email address. If the
address is going to be placed in a hyperlink that is displayed publically,
with validation an attacker can inject Javascript into your page:

<a href="mailto: $address">

if $address is "><script src="123.45.2.1/a.js">

then the output becomes

<a href="mailto: "><script src="123.45.2.1/a.js">">

Uzytkownik "John Dunlop" <john+usenet@jo hndunlop.info> napisal w wiadomosci
news:MPG.1a95c2 465fa6d64a98968 d@News.Individu al.NET...[color=blue]
> Rahul Anand wrote:
>[color=green]
> > You can find a regular expression to validate email-address here:
> >
> > http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html[/color]
>
> This is a Perl module which validates email addresses against the
> syntax of RFC822 (obsoleted by RFC2822); the pattern itself will not
> match all valid email addresses, despite its complexity.
>[color=green]
> > Try using this if it worth using for your email-validation :)[/color]
>
> Validating the syntax of an email address and finding it exists is
> not proof of it being in use. If you'd like to know that what a user
> entered is really her email address, then a confirmation mail is the
> best way, as both the CGI FAQ and the Mail::RFC822::A ddress
> documentation recommend.
>
> --
> Jock[/color]

**John Dunlop** · Jul 17 '05, 03:22 AM

Re: Finding @ in a string, and other items

Chung Leong wrote upsidedown:
[color=blue]
> I just thought of a reason to validate the syntax of a email address. If the
> address is going to be placed in a hyperlink that is displayed publically,
> with validation an attacker can inject Javascript into your page:
>
> <a href="mailto: $address">
>
> if $address is "><script src="123.45.2.1/a.js">
>
> then the output becomes
>
> <a href="mailto: "><script src="123.45.2.1/a.js">">[/color]

If you're inserting user-supplied data into your document, and only
checking said data conforms to RFC(2)822 address syntax, you've still
got problems. Imagine this syntactically valid address in the
situation above:

"><script src='scheme:123 .45.2.1/a.js'>"@domain. example

(It's essential to use an absolute URI, otherwise the src value will
be interpreted as a relative URI. Adding the required type
attribute, obligatory SCRIPT end-tag, and the A element's end-tag,
could conceivably result in a valid document!)

Presumably, however, if the address is to be used as part of an URL,
you'd URL encode it, after separating it into its component parts.
This is a hypothetical discussion. :-)

--
Jock

Finding @ in a string, and other items

Finding @ in a string, and other items

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment