Perl code to differentiate numeric and non-numeric input

Shell Programming and Scripting
1

Hi All,

Is there any code in Perl which can differentiate between numeric and non-numeric input?

2

The most common way:
Use regular expression.

Alternative (probably a better) way:

cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("-8.90e10")?"Looks like a number.\n":"Not a number.\n")'
Looks like a number.
cbkihong@cbkihong:~$ perl -MScalar::Util -e 
'print(Scalar::Util::looks_like_number("89d")?"Looks like a number.\n":"Not a number.\n")'
Not a number.
3

Hi ,

Below is my Perl code using regular expression. but it doesn;t seem to work.
Can anybody tell me what's wrong with my code ?

#!/usr/bin/perl

print "Enter a term: ";
$Input = <STDIN>;
print "\n";

if ($input == [0-9]) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}
4 
#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ($input =~ /^[0-9]+$/) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}
5

i don't intend to flame you, but wish to point out a few deficiencies in your code - it doesn't consider negative numbers, and real numbers, in current form, it is identifying natural numbers, along with zero

6

this one identifies integers, real numbers, and negative numbers as well:

#!/usr/bin/perl
use strict;

print "Enter a number: ";
chomp (my $num = <STDIN>);

if ($num =~ m/^-?\d+$/) {
    print "An integer \n";
}
elsif ($num =~ m/^-?\d+[\/|\.]\d+$/) {
    print "real number! \n";
}
else {
    print "not a number \n";
}
7 
#!/usr/bin/perl

print "Enter a term: ";
$input = <STDIN>;
print "\n";

if ( $input =~ /^[\+-]*[0-9]*\.*[0-9]*$/ && $input !~ /^[\. ]*$/  ) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}
8

if you don't want to consider --45 as numeric:

if ( $input =~ /^[\+-]?[0-9]*\.*[0-9]*$/ && $input !~ /^[\. ]*$/ ) {

and 56..34 doesn't seem to be numeric, so how about:

if ( $input =~ /^[\+-]?[0-9]*\.?[0-9]*$/ && $input !~ /^[\. ]*$/ ) {
9

Hi Anbu,
I tried your code but it's not working.

$ cat xxx.pl
#!/usr/bin/perl

print "Enter a term: ";
$Input = <STDIN>;

if ($input =~ /[3]*[0-9]*\.*[0-9]$/ && $input !~ /[4]$/) {
print "$Input is numeric\n";
}
else {
print "$Input is non-numeric\n";
}
$ perl xxx.pl
Enter a term: 10
10
is non-numeric
$ perl xxx.pl
Enter a term: 23
23
is non-numeric

  1. \+- ↩︎

  2. \. ↩︎

  3. \+- ↩︎

  4. \. ↩︎

10 
$Input = <STDIN>;

if ($input =~ /^[\+-]*[0-9]*\.*[0-9]*$/ && $input !~ /^[\. ]*$/) {

Variable names are case sensitive and also incorporate the Yogesh Sawants comments.

$input = <STDIN>;

if ( $input =~ /^[\+-]?[0-9]*\.?[0-9]*$/ && $input !~ /^[\. ]*$/ ) {
11

Hi Anbu,

Thanks for the guidance. it works fine now!

12

How to invoke the above perl code in ksh script.

Thanks in adv.

Br//
Vijay