updated shell scripts

Author: learnbyexample

example_files/shell_scripting/comments.sh

@@ -0,0 +1,2 @@
+# this is a comment on its own line
+echo 'hello' # and this is a comment after a command

example_files/shell_scripting/if_then_else.sh

@@ -3,7 +3,7 @@ if (( $# != 1 )) ; then
     exit 1
 else
     if [[ ! -f $1 ]] ; then
-        echo "Error! '$1' is not a valid file" 1>&2
+        printf 'Error! %q is not a valid file\n' "$1" 1>&2
         exit 1
     else
         echo "No. of lines in '$1' is $(wc -l < "$1")"