Regular Expression Help

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

Hi Monks,
I have a string of numbers that comes into my program that supposable, it should have 6 digits long, like 123456, but sometimes it will come in to the program with 4 or 5 digits only, when that happens I have to add 0's to complement the string to have 6 digits.
Like if a string of number comes in with 1234, I have to add 0's to it like, 001234, so it can have 6 digits.
I have a regular expression that isn't working but my question is what is the best way to do this?

if($u=~/\d{4}?/){$u=~s/\d\d\d\d/00$u/;}
if($u=~/\d{5}?/){$u=~s/\d\d\d\d\d/0$u/;}
[download]

The code above isn't working because in both cases it match the digits it finds.
Thank you!

Comment on Regular Expression Help Download Code

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Re: Regular Expression Help by davidrw (Prior) on Jun 28, 2005 at 17:48 UTC
Best way is with sprintf: `$u = sprintf "%06d", $u;` [download] If you want to use a substitution, you could do: `$u =~ s/(\d+)/"0"x(6-length($1)).$1/e; if length($u) < 6;` [download] Update: To correct your attempt: `if($u=~/^\d{4}$/){$u=~s/\d\d\d\d/00$u/;} if($u=~/^\d{5}$/){$u=~s/\d\d\d\d\d/0$u/;} # but better written as: # $u = "00$u" if $u =~ /^\d{4}$/; # $u = "00$u" if length($u) == 4; # if you know it's digits` [download]	[reply] [d/l] [select]
Re: Regular Expression Help by Transient (Hermit) on Jun 28, 2005 at 17:46 UTC
`$u = ('0' x (6-length($u))).$u;` [download]	[reply] [d/l]
Re^2: Regular Expression Help by Anonymous Monk on Jun 28, 2005 at 17:53 UTC
Hi interesting, can you give me an explaination on this code? Thanks!	[reply]
Re^3: Regular Expression Help by Transient (Hermit) on Jun 28, 2005 at 17:58 UTC
Sure! Basically if you take where we started : `$u = ('0' x (6-length($u))).$u;` we can break this up into multiple statements: `$length_of_u = length($u); # how long is this string? $how_many_characters_short = 6-$length_of_u; # how far are we from ha +ving 6 characters? $padding = '0' x $how_many_characters_short; # this will give us as ma +ny 0's as $how_many_characters_short is long (e.g. if it is 4 - it gi +ves us '0000') $u = $padding.$u; # concatenate them together... finished!` [download] HTH!	[reply] [d/l] [select]
Re^4: Regular Expression Help by Anonymous Monk on Jun 28, 2005 at 18:01 UTC
Re: Regular Expression Help by kirbyk (Friar) on Jun 28, 2005 at 17:50 UTC
There's More Than One Way To Do It! I prefer: $u = sprintf("%06d", $u); -- Kirby, WhitePages.com	[reply]
Re: Regular Expression Help by Forsaken (Friar) on Jun 28, 2005 at 17:50 UTC
printf is your friend. `printf("%06d", $string);`(untested) should do the trick. Remember rule one...	[reply] [d/l]