#
# Usage: $0 required_space [filesystem]
# required_space = nnn[unit]  unit=Bytes, Kilo, Mega, Giga
# filesystem, default ='.'

: ${1:?'You must specify required free space'}

df -k ${2:-.} | tail -1 | \
awk -v Required=$1 '
BEGIN {
   Required = toupper(Required);
   if (Required !~ /^[0-9]+(\.[0-9]*)?[BKMG]?$/) {
      print "Invalid value for required free space: " Required;
      exit 1;
   }
   if (Required ~ /[BKMG]$/) {
      len = length(Required);
      unit = substr(Required,len,1);
      Required = substr(Required,1,len-1);
   } else {
      unit = "B";
   }
   if      (unit == "G")
        Required = Required * 1024 * 1024;
   }
   if      (unit == "G")
        Required = Required * 1024 * 1024;
   else if (unit == "M")
        Required = Required * 1024;
   else if (unit == "B")
        Required = (Required + 1023) / 1024;
   Required = int(Required + .999);

   print "Required free space : " Required " K";
}
{
   Free = $4;
   print "Free space : " Free "K";
   if (Free > Required) {
      print "\nRequired free space available";
      exit;
   } else {
      print "\nNot enought free space available" ;
      exit 1;
   }
}
'