1 files changed, 12 insertions, 0 deletions
diff --git a/resize.sh b/resize.sh
index 24baaf7..f49a1a5 100755
--- a/resize.sh
+++ b/resize.sh
@@ -6,6 +6,18 @@
 if [ -z $1 ] 
 	then reduce=25
 	else reduce=$1
+        re='^[0-9]+$'       # reg expression for digits only
+        if ! [[ $reduce =~ $re ]] 
+            then
+                echo "Usage: If you use arguments, arg 1 (resize percentage) must be an integer"
+                exit 1
+            else
+                # arg1 is an integer
+                if [ $reduce -gt 99 ] || [ $reduce -lt 1 ] ; then
+                    echo "Usage: reduction percentage must be between 1 and 99 percent"
+                    exit 1
+                fi
+        fi
 fi
 
 # Check for folder name in command line (no spaces of course!)