remove spaces fom filename

Having a space in the file name is never a good idea.
If you are in need to remove space from all file names
within your current directory you can use a following
command to do so:

ls | grep " " | while read -r f; do mv -i "$f" `echo $f | tr -d ' '`; done

In case that you wich to substitute space within a file
name to underscore ( or any other character ) use a following
command to do so:

ls | grep " " | while read -r f; do mv "$f" `echo $f | tr ' ' '_'`; done

How it works? ls and grep will feed while loop with all files within
a current working directory which contain a space in their file name.
In the body of the while loop we will next execute mv command a translate
it file destination with tr command. Make sure to keep -i option enabled
when using mv command to avoid accidentally overwrite files.