Need help with regexp

Posted by Gunner on Tue 30 Mar 2021 03:51 AM — 4 posts, 17,735 views.

Gunner Argentina Tue 30 Mar 2021 03:51 AM #0

Hello.
I am trying to validate text input from an input box.
What I need is for the character string to match a word (not numbers) or two words separated by a space
the function is:


function comprobar_hechizo (dhech)
  local match = string.match (dhech, "^%%a+%%s%%a+$")
  if not n then
    utils.msgbox ("the spell name can only contain letters and spaces", "Error")
  return false
  end
return true
end

This only works if the string contains two words and a space, but I also want it to work if the string contains only one word.
I have tried this:


  local match = string.match (dhech, "^%%a+|%%a+%%s%%a+$")

But don't work.

Nick Gammon Australia Forum Administrator Tue 30 Mar 2021 04:35 AM #1

What's with the two % symbols?

Anyway, Lua patterns don't have optional things (however the PCRE regexps, used in triggers, do).

You could do this:


test = "foo bar"

if string.match (test, "^[%a%s]+$") then
  print "ok"
else
  print "fail"
end

That will test for letters and spaces, so it would match one word, two words, three or more words, or even a single space.

A better thing would be to have two tests (one word, or two words) like this:


test = "foo bar"

if string.match (test, "^%a+$") or string.match (test, "^%a+%s+%a+$") then
  print "ok"
else
  print "fail"
end

Nick Gammon Australia Forum Administrator Tue 30 Mar 2021 04:40 AM #2

Although this might work:


test = "foo bar"

if string.match (test, "^%a+%s*%a*$") then
  print "ok"
else
  print "fail"
end

That is testing for:

One or more letters (so you get at least one word)
Zero or more spaces (so the space is optional)
Zero or more extra letters (to allow for the second word)

See: http://www.gammon.com.au/scripts/doc.php?lua=string.find

Gunner Argentina Tue 30 Mar 2021 04:52 AM #3

Nick Gammon said:

A better thing would be to have two tests (one word, or two words) like this:


test = "foo bar"

if string.match (test, "^%a+$") or string.match (test, "^%a+%s+%a+$") then
  print "ok"
else
  print "fail"
end

Perfect, that has worked for me.
As for the double%, that function is inside a send in an alias