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Checking if field contains numbers

Posted on 2000-04-19
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Last Modified: 2010-03-05
Hi!

How can I tell if $FORM{count} only contains numbers, therefore no letters etc.

Thanks in advance,

Graeme Sandwell
graeme@officedevil.co.uk
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Question by:graemesandwell
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3 Comments
 
LVL 16

Accepted Solution

by:
maneshr earned 100 total points
ID: 2730839
You want to check whether a string represents a valid number. This is a common problem when validating input, as in a CGI script.


This problem gets to the heart of what we mean by a number. Even things that sound simple, like integer, make you think hard about what you will accept ("Is a leading + for positive numbers optional, mandatory, or forbidden?").


You must decide what you will and will not accept. Then, construct a regular expression to match those things alone. Here are some precooked solutions  for most common cases.


## Sample value.
$FORM{count}="1298";

## Eliminate any leading and trailing spaces from the variable
$FORM{count}=~ s/^\s+//;
$FORM{count}=~ s/\s+$//;

## Now check...
if ($FORM{count}!~ /^\d+$/){ # rejects -3
  print "not a natural number\n";
}

if ($FORM{count}!~ /^-?\d+$/){ ## rejects +3
  print "not an integer\n";
}

if ($FORM{count}!~ /^[+-]?\d+$/){
  print "not an integer\n";
}

if ($FORM{count}!~ /^-?\d+\.?\d*$/){ ## rejects .2
  print "not a decimal number\n";
}

if ($FORM{count}!~ /^-?(?:\d+(?:\.\d*)?|\.\d+)$/){
  print "not a decimal number\n";
}
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LVL 84

Expert Comment

by:ozo
ID: 2731686
perldoc -q "How do I determine whether a scalar is a number/whole/integer/float"
0
 

Author Comment

by:graemesandwell
ID: 2737606
Thanks for all the time you put into your answer!  I was looking for a number > 0.

Thanks again!

Graeme Sandwell
0

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