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Full Discussion: Read only number
Top Forums Shell Programming and Scripting Read only number Post 302418309 by jim mcnamara on Monday 3rd of May 2010 08:49:30 PM
Old 05-03-2010
one way is to chck each lelemnt of the string to see if it is a numeric character

Code:
while :
do
  echo "enter a number: \c"
  read number
  len=${#number}
  testvar=$(echo "$number" | tr -dc '[:digit:]')   # remove non-numeric chars from $number
  if [[ $len -ne ${#testvar} ]] ; then  # if you had all numeric chars they would be the same length
      echo "$number is not a number"  # error message
  else
      break      #exit the loop
  fi
done 
#... more code goes here to work with the number

 

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English(3pm)						 Perl Programmers Reference Guide					      English(3pm)

NAME
English - use nice English (or awk) names for ugly punctuation variables SYNOPSIS
use English; use English qw( -no_match_vars ) ; # Avoids regex performance penalty # in perl 5.16 and earlier ... if ($ERRNO =~ /denied/) { ... } DESCRIPTION
This module provides aliases for the built-in variables whose names no one seems to like to read. Variables with side-effects which get triggered just by accessing them (like $0) will still be affected. For those variables that have an awk version, both long and short English alternatives are provided. For example, the $/ variable can be referred to either $RS or $INPUT_RECORD_SEPARATOR if you are using the English module. See perlvar for a complete list of these. PERFORMANCE
NOTE: This was fixed in perl 5.20. Mentioning these three variables no longer makes a speed difference. This section still applies if your code is to run on perl 5.18 or earlier. This module can provoke sizeable inefficiencies for regular expressions, due to unfortunate implementation details. If performance matters in your application and you don't need $PREMATCH, $MATCH, or $POSTMATCH, try doing use English qw( -no_match_vars ) ; . It is especially important to do this in modules to avoid penalizing all applications which use them. perl v5.18.2 2014-01-06 English(3pm)
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