Regex: Specifying quantity for bracketed items

Hagbone has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Regex: Specifying quantity for bracketed items by tall_man (Parson) on Nov 10, 2004 at 21:21 UTC
You aren't matching what you think you are. The `[^ ]+` greedily matches all the letters and numbers but one, as this example will show: `$_ = "\@abcde99\@"; if (/^([^ ]+)([a-z0-9]+)([^ ]+)$/) { # prints: @abcde99@ print "$1$2$3\n"; }` [download] A better regex might be this one: `$_ = "\@abcde99\@"; if (/^([^ ]+?)([a-z0-9]{5,12})([^ a-z0-9]+)$/) { print "$1$2$3\n"; }` [download]	[reply] [d/l] [select]
Re: Regex: Specifying quantity for bracketed items by tachyon (Chancellor) on Nov 10, 2004 at 21:32 UTC
The reason that your RE does not work as expect is that the `[^ ]+` atom will match any number of non space chars, which effectively makes your 5,12 limit useless. You first regex is also (probably) broken as it will match all sorts of non lowercase stuff. Here is what it does: `while(<DATA>) { chomp; print "Matches like: ($1)($2)($3)\n" if m/^([^ ]+)([a-z0-9]+)([^ ] ++)$/ } __DATA__ >>>>this<<<< $$$$that$$$$` [download] As suggested you probably want `m/^[a-z0-9]+$/` which will only match strings that are lowercase or numbers. Changing the + to {MIN,MAX) limits the number. If you want something special at the begining or end of the string using lookback and lookahead assertions may be relevant. However given that a space is not part of your match class..... cheers tachyon	[reply] [d/l] [select]
Re: Regex: Specifying quantity for bracketed items by injunjoel (Priest) on Nov 10, 2004 at 21:17 UTC
Greetings all, would something like this work? `/^[a-z0-9]{5,12}$/i` [download] The ^ and $ will ensure that the string doesn't start or end with a space. -InjunJoel "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo	[reply] [d/l]
Re: Regex: Specifying quantity for bracketed items by ikegami (Patriarch) on Nov 10, 2004 at 21:36 UTC
Maybe you want something like this: `/ ^(?![ ]) # Doesn't start with a space .? # Anything [a-z0-9]{5,12} # Has a 5..12 lowercases or digits in a row . # Anything (?<![ ])$ # Doesn't end with a space /x` [download] which will match `a1b2c3` `BVBDa1b2c3` `a1b2c3ZZZ` `!@#a1b2c3$%^` `! a1b2c3 FF`	[reply] [d/l] [select]
Re^2: Regex: Specifying quantity for bracketed items by Eimi Metamorphoumai (Deacon) on Nov 10, 2004 at 22:07 UTC
Actually, that doesn't limit you to 5..12, that matches anything with at least 5 lowercases or digits in a row. Any more than 12 just get sucked into the `.` after it. Which makes it equivalent to `/ ^(?![ ]) # Doesn't start with a space .? # Anything [a-z0-9]{5} # Has 5 lowercases or digits in a row .* # Anything (possibly more lowercases or digits) (?<![ ])$ # Doesn't end with a space /x` [download]	[reply] [d/l] [select]
Re^3: Regex: Specifying quantity for bracketed items by ikegami (Patriarch) on Nov 10, 2004 at 22:10 UTC
Right you are! Fixed below. `/ ^(?![ ]) # Doesn't start with a space .? # Anything (?<![a-z0-9]) # For the {5,12} to be meaningful. [a-z0-9]{5,12} # Has a 5..12 lowercases or digits in a row (?![a-z0-9]) # For the {5,12} to be meaningful. . # Anything (?<![ ])$ # Doesn't end with a space /x` [download]	[reply] [d/l]
Re: Regex: Specifying quantity for bracketed items by Hagbone (Monk) on Nov 11, 2004 at 00:05 UTC
Ahhh the post (albiet corrected) above appears to be just what I was looking for .... many, many thanks. Regex's ..... if brains were muscles, regex's would be a prescribed workout (at least for me;) Thanks much to all who replied	[reply]