diff --git a/scripts/_common b/scripts/_common
index 9584cf1..f526a9b 100644
--- a/scripts/_common
+++ b/scripts/_common
@@ -10,6 +10,34 @@ ALL_QUIET () {  # Redirige la sortie standard et d'erreur dans /dev/null
   $@ > /dev/null 2>&1
 }
 
+CHECK_VAR () {  # Check variable is not empty
+# $1 = Checking variable
+# $2 = Text to display on error
+  test -n "$1" || (echo "$2" >&2 && false)
+}
+
+CHECK_PATH () { # Checks / at the beginning of the path. And his absence at the end.
+  if [ "${path:0:1}" != "/" ]; then    # If the first character is not /
+    path="/$path"    # Add / at the beginning of path
+  fi
+  if [ "${path:${#path}-1}" == "/" ] && [ ${#path} -gt 1 ]; then    # If the last character is a / and it is not the only character.
+    path="${path:0:${#path}-1}" # Delete last character
+  fi
+}
+
+CHECK_DOMAINPATH () { # Checks the availability of the path and domain.
+  sudo yunohost app checkurl $domain$path -a $app
+}
+
+CHECK_FINALPATH () {  # Checks that the destination folder is not already in use.
+  final_path=/var/www/$app
+  if [ -e "$final_path" ]
+  then
+    echo "This path already contains a folder" >&2
+    false
+  fi
+}
+
 # Substitute a string by another in a file
 #
 # usage: ynh_substitute_char string_to_find replace_string file_to_analyse
diff --git a/scripts/install b/scripts/install
index 205522c..73f73f8 100644
--- a/scripts/install
+++ b/scripts/install
@@ -14,23 +14,22 @@ is_public=$YNH_APP_ARG_IS_PUBLIC
 
 app=$YNH_APP_INSTANCE_NAME
 
-# Check domain/path availability
-sudo yunohost app checkurl "${domain}${path}" -a "$app" \
-    || ynh_die "Path not available: ${domain}${path}"
+CHECK_VAR "$app" "app name not set"
 
-# Remove trailing "/" for next commands
-if [[ ! "$path" == "/" ]]; then
-    path=${path%/}
-fi
+CHECK_PATH
+
+CHECK_DOMAINPATH
+
+CHECK_FINALPATH
+
+# Create system user dedicace for this app
+ynh_system_user_create $app
 
 # Copy files to the right place
 final_path=/var/www/$app
 sudo mkdir -p $final_path
 extract_source $final_path
 
-# Create system user dedicace for this app
-ynh_system_user_create $app
-
 # Copy files to the right place with the right permissions
 final_path=/var/www/$app
 sudo mkdir -p $final_path