09-21-2005
How to check whether a string is number or not
Hi ,
I am facing a problem .. which looks simple... but took 2 days of mine.. even now it is not solved completely..
I have one variable..., want to know whether that variable contains number... canbe +ve or -ve ...
Values
+35 --- number
-43 --- number
45A -- non number
34+45 -- non number
please help me
Shihab
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re(3pm) Perl Programmers Reference Guide re(3pm)
NAME
re - Perl pragma to alter regular expression behaviour
SYNOPSIS
use re 'taint';
($x) = ($^X =~ /^(.*)$/s); # $x is tainted here
$pat = '(?{ $foo = 1 })';
use re 'eval';
/foo${pat}bar/; # won't fail (when not under -T switch)
{
no re 'taint'; # the default
($x) = ($^X =~ /^(.*)$/s); # $x is not tainted here
no re 'eval'; # the default
/foo${pat}bar/; # disallowed (with or without -T switch)
}
use re 'debug'; # NOT lexically scoped (as others are)
/^(.*)$/s; # output debugging info during
# compile and run time
use re 'debugcolor'; # same as 'debug', but with colored output
...
(We use $^X in these examples because it's tainted by default.)
DESCRIPTION
When "use re 'taint'" is in effect, and a tainted string is the target of a regex, the regex memories (or values returned by the m// opera-
tor in list context) are tainted. This feature is useful when regex operations on tainted data aren't meant to extract safe substrings,
but to perform other transformations.
When "use re 'eval'" is in effect, a regex is allowed to contain "(?{ ... })" zero-width assertions even if regular expression contains
variable interpolation. That is normally disallowed, since it is a potential security risk. Note that this pragma is ignored when the
regular expression is obtained from tainted data, i.e. evaluation is always disallowed with tainted regular expresssions. See "(?{ code
})" in perlre.
For the purpose of this pragma, interpolation of precompiled regular expressions (i.e., the result of "qr//") is not considered variable
interpolation. Thus:
/foo${pat}bar/
is allowed if $pat is a precompiled regular expression, even if $pat contains "(?{ ... })" assertions.
When "use re 'debug'" is in effect, perl emits debugging messages when compiling and using regular expressions. The output is the same as
that obtained by running a "-DDEBUGGING"-enabled perl interpreter with the -Dr switch. It may be quite voluminous depending on the complex-
ity of the match. Using "debugcolor" instead of "debug" enables a form of output that can be used to get a colorful display on terminals
that understand termcap color sequences. Set $ENV{PERL_RE_TC} to a comma-separated list of "termcap" properties to use for highlighting
strings on/off, pre-point part on/off. See "Debugging regular expressions" in perldebug for additional info.
The directive "use re 'debug'" is not lexically scoped, as the other directives are. It has both compile-time and run-time effects.
See "Pragmatic Modules" in perlmodlib.
perl v5.8.0 2002-06-01 re(3pm)