regex

craig467 · 03-02-2007, 12:31 PM

I have a form collecting data including a city name. People are not paying attention and I am collecting strange city names. Is there a way to check that only letters and single spaces have been added in the field. I found out how to remove the leading spaces and trailing spaces with this:

Code:

$city =~ s/^ +//;  #Remove leading spaces
$city =~ s/ +$//;  #Remove trailing spaces

but I am having trouble using the m//operator so that it will accept "San Francisco", "Augusta", "Miami" and reject anything with a number, punctuation or multiple spaces in it.

What I have so far is this:

Code:

if ($city !~ m/[a-zA-Z ]+/) {
    #print error message
}

But that is not working. I tried \b[a-zA-Z ]+\b among other things that did not work and so I am stuck, can someone help?

Vookimedlo · 03-02-2007, 12:47 PM

for example:

Code:

if ($city =~m/[ \t]{2,}/ or $city !~m/^[a-zA-Z ]+$/) {
	print "message\n"
}

craig467 · 03-02-2007, 03:30 PM

That is incredible.

I would love to know how this stuff makes sense to people, I have not caught on to the logic of regex yet, but I want to. Just bought a book called "Regular Expressions The complete Tutorial" by Jan Goyvaerts and am waiting for it to come. I hope that after reading that, it will make more sense!

Thanks again! I really appreciate it.

theNbomr · 03-02-2007, 04:17 PM

Quote:

Originally Posted by Vookimedlo

for example:

Code:

if ($city =~m/[ \t]{2,}/ or $city !~m/^[a-zA-Z ]+$/) {
	print "message\n"
}

Not sure what you are trying to filter with that first regex '/[ \t]{2,}/', which I read as 'exactly two tabs, spaces, or combination thereof'. I cannot see how that serves any useful purpose. Can you explain?
I think the original poster can improve the leading/trailing whitespace trimmer with something like

Code:

$city =~ s/^\s+//;  #Remove leading spaces
$city =~ s/\s+$//;  #Remove trailing spaces

This is more general, and removes tabs, etc.

--- rod.

craig467 · 03-02-2007, 06:12 PM

Quote:

Originally Posted by theNbomr

Not sure what you are trying to filter with that first regex '/[ \t]{2,}/', which I read as 'exactly two tabs, spaces, or combination thereof'. I cannot see how that serves any useful purpose. Can you explain?
I think the original poster can improve the leading/trailing whitespace trimmer with something like

Code:

$city =~ s/^\s+//;  #Remove leading spaces
$city =~ s/\s+$//;  #Remove trailing spaces

This is more general, and removes tabs, etc.

--- rod.

Thanks theNbomr, I fixed the leading/trailing spaces and understand your reasoning - thanks for posting.

As for the '/[ \t]{2,}/', I understood it the way you explained it, but just figured it was my inexperience with regex that was not translating it correctly. I entered in what what posted and it does what I needed it to do which was great, but I am sure I could not explain it. This regex still seems a little smoke and mirrors to me, but I am determined to make sense out of it, seems that it will just take some time.

Vookimedlo · 03-03-2007, 04:39 AM

Quote:

Originally Posted by theNbomr

Not sure what you are trying to filter with that first regex '/[ \t]{2,}/', which I read as 'exactly two tabs, spaces, or combination thereof'. I cannot see how that serves any useful purpose. Can you explain?

Craig467 wrote that he want to: "reject anything with a number, punctuation or multiple spaces in it." And regex '/[ \t]{2,}/' catchs all strings that contain 2 or more white characters.

bigearsbilly · 03-03-2007, 09:09 AM

your match is matching if it finds a character,
you need to match a non-char like so:

Code:

if ($city =~ m/[^a-zA-Z ]+/) {
    #print error message
}

think about it
m/[a-z/ will match 123a because it finds a char.
m/[^a-z]/ will not match "abc" because it doesn't find a non-char.
but will match "abc1" because it finds a non char