Shell Programming and Scripting

#!/usr/bin/ksh
file="sslexpiry" #the file where you keep your string expiry date

name=$(cat "$file")        #the output of 'cat $file' is assigned to the $name variable
 
date > todate.ext #the file where you keep current date value

file1="todate.ext"  #the file where you keep your string current date

todaydate=$(cat "$file1") #the output of 'cat $file1' is assigned to the $todaydate variable
 
 
echo $name
echo $todaydate

Fri Apr 10 18:59:59 CDT 2015
Thu Feb 19 18:50:52 CST 2015

days=`perl -e 'use Date::Parse; print int((str2time($ARGV[1])-str2time($ARGV[0]))/86400);' "$name" "$todaydate"`
if [ "$days" -lt 30 ]; then
   echo "send mail..."
fi

days=$(( (`date --date="$name" +%s` - `date --date="$todaydate"  +%s`)/86400 ))
if [ "$days" -lt 30 ]; then
   echo "send mail..."
fi