examples/functions/isnum.bash

   1 #From: jrmartin@rainey.blueneptune.com (James R. Martin)
   2 #Newsgroups: comp.unix.shell
   3 #Subject: Re: testing user input on numeric or character value
   4 #Date: 26 Nov 1997 01:28:43 GMT
   5
   6 # isnum returns True if its argument is a valid number,
   7 # and False (retval=1) if it is any other string.
   8 # The first pattern requires a digit before the decimal
   9 # point, and the second after the decimal point.
  10
  11 # BASH NOTE: make sure you have executed `shopt -s extglob' before
  12 # trying to use this function, or it will not work
  13
  14 function isnum # string
  15 {
  16     case $1 in
  17     ?([-+])+([0-9])?(.)*([0-9])?([Ee]?([-+])+([0-9])) )
  18         return 0;;
  19     ?([-+])*([0-9])?(.)+([0-9])?([Ee]?([-+])+([0-9])) )
  20         return 0;;
  21     *) return 1;;
  22     esac
  23 }