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Perl Regular Expression?

I need to write a regular expression where the question marks are in the code code is below. The $var1 will be a value where only numbers and a period are ok.

Valid values would be:
1.0001
2.3
0.2

Invalid would be any letters, a comma, other characters, etc...
Only numbers and a period are valid.

Please post an answer and explanation of what it does. I'm terrible at regular expressions and in a hurry to finish some code, but still trying to learn them as I go! Thanks!

if( $var1 ~= ???? ){
    print "true";
}else{
    print "false";
}

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Pratima

^\d+(\.\d)?$

Pratima

refr
http://work.lauralemay.com/samples/perl.html

ozo

perldoc -q "How do I determine whether a scalar is a number/whole/integer/float"
Found in perlfaq4.pod
How do I determine whether a scalar is a number/whole/integer/float?

Assuming that you don't care about IEEE notations like "NaN" or
"Infinity", you probably just want to use a regular expression.

if (/\D/) { print "has nondigits\n" }
if (/^\d+$/) { print "is a whole number\n" }
if (/^-?\d+$/) { print "is an integer\n" }
if (/^[+-]?\d+$/) { print "is a +/- integer\n" }
if (/^-?\d+\.?\d*$/) { print "is a real number\n" }
if (/^-?(?:\d+(?:\.\d*)?|\.\d+)$/) { print "is a decimal number\n" }
if (/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/)
{ print "a C float\n" }

There are also some commonly used modules for the task. Scalar::Util
(distributed with 5.8) provides access to perl's internal function
"looks_like_number" for determining whether a variable looks like a
number. Data::Types exports functions that validate data types using
both the above and other regular expressions. Thirdly, there is
"Regexp::Common" which has regular expressions to match various types
of numbers. Those three modules are available from the CPAN.

If you're on a POSIX system, Perl supports the "POSIX::strtod"
function. Its semantics are somewhat cumbersome, so here's a "getnum"
wrapper function for more convenient access. This function takes a
string and returns the number it found, or "undef" for input that isn't
a C float. The "is_numeric" function is a front end to "getnum" if you
just want to say, "Is this a float?"

sub getnum {
use POSIX qw(strtod);
my $str = shift;
$str =~ s/^\s+//;
$str =~ s/\s+$//;
$! = 0;
my($num, $unparsed) = strtod($str);
if (($str eq '') || ($unparsed != 0) || $!) {
return undef;
}
else {
return $num;
}
}

sub is_numeric { defined getnum($_[0]) }

kaufmed

pratima_mcs' solution is close, except that it won't handle your first sample: 1.0001. The correction is small though:

^\d+(?:\.\d+)?$

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As for the explanation:

^          Beginning of string
\d+        One-or-more ( + ) of a digit ( \d )
(? ... )   Non-capturing group -- treat everything inside as one unit
\.         Literal period
\d+        One-or-more ( + ) of a digit ( \d )
?          Zero-or-one. Modifies the thing to the left, which in this case is the non-capturing group
$          End of string

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KGNickl

ASKER

m/^\d*\.\d+$/

ASKER CERTIFIED SOLUTION

kaufmed

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KGNickl

ASKER

Award kaufmed points. I didn't look at new answers after 11:00 this morning and then just closed it w/ adding my comments. So that answer is good and can be awarded points, just was after I already located the answer earlier in the morning.