There are a few ways of renaming a list of files, replacing the spaces inside their names with underscore (_) or dashes (-) or whatever.

Here's the method I used:

1) The list of files from before replacement

2) The loop that does the replacement:

ls *.mp3 | sed 's/ /|/g' replaces spaces " " with pipes "|" in the output of ls command ( I choosed pipe because no file had in it's name's componence this special char) so that the for loop will take line by line, not word by word, separated by space. Next in the old variable it is set the name of the file (replacing the pipe back to space). Now that the old name of the file is set correctly, we move the file (mv "$old") to a new file called `echo $i | sed /s/|/_/g'`, meaninga new file that instead of pipe (|) it has underscore (_).

Note: This method will not work on all filenames. If one of the files in the list contains a pipe (|) in it's name before running this command, then this file will most probably fail to be renamed so there would be 2 options: rename manually this file or not using the pipe as delimiter, but rather a combination of special chars, like "/|" or something similar that is very unprobably to be in the composition of an existing file.

3) The new list of files after they all've been renamed and spaces replaced with underscores

I've also tested this with ls|xargs, find -print|xargs and -J option but nothing worked like this method.

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