Re: Regular expression to find from start of string to first space

On Tue, August 8, 2006 4:21 am, Dave M G wrote: > Shouldn't this regular expression select everything from the start of > the string to the first space character: > > $firstWord = preg_match('#^*(.*) #iU', $word); > > It doesn't, so clearly I'm wrong, but here's why I thought it would: > > The enclosing has marks, "#", I *think* just encloses the expression. > I > was told to use them before, but I can't find them here: > http://jp2.php.net/manual/en/reference.pcre.pattern.syntax.php The # can be any character you want, that's convenient. Convenient generally means "not likely to be needed within the pattern" The #, or whatever you choose, marks beginning and end of the pattern. I believe that there are also some special ones like < and > that you can use. > The caret, "^", says to start at the beginning of the line. Yes. > The first asterix, "*" after the caret says to use any starting > character. No. * means "0 or more of the preceding thingie" * by itself, with nothing preceding it... I don't even know WHAT that means. Maybe it's just a * sometimes a star is just a star :-) Or maybe it applies to the "beginning of string" anchor, so it would match "0 or more" newlines if you were using 's' at the end... But the whole point of ^ is to require a start, and the whole point of * is to not require anything at all, so that would be a oxymoron. > The space just before the second "#" is the closing character of my > search. No. The # is the closing of your pattern, because you CHOSE # as the beginning of your pattern. These are all the same: #^(.*)\s# |^(.*)\s| /^(.*)\s/ Z^(.*)\sZ Z is probably not such a good idea as you may need a Z in your pattern. It may even be illegal and you can only use non-alphanumeric for the delimiter, actually. > The "(.*)" in the middle says to take anything in between the > beginning > of the line and the space. > > "iU" says, "be case insensitive, and don't be greedy". Yes. Without that, the .* would match spaces as well as non-spaces, and only the LAST whitespace would "count" for the \s bit. > So, it should start at the beginning of the line and get everything up > to the first space. But it doesn't work. I generally find .* to be problematic, and do more like: #^([^\s])*#sU This way, I'm saying to anchor at the beginning, and then look for NON-whitespace, and use * to get as many as possible. The ^ *inside* the [] means "not" -- Like Music? http://l-i-e.com/artists.htm