That is one bizarre line of sh script. I'm not sure what it is that you think it does, but this is what it's actually doing:

ls prints the name of each item in the directory, one line per item.

If there is a space or tab in the filename, awk will only print the first word of the name.

The list of names is then passed to printf. The first argument to printf will be treated as the format string. The output of printf will depend on the contents of the first pathname emitted by ls. If there are no conversion specifiers in the name, only that first pathname is printed. If there are conversion specifiers, the output depends on their number and type.

Whatever comes out of printf goes through tr where space characters are removed. Unless you're trying to delete uncommon whitespace, such as vertical tabs, form feeds, or carriage returns, tr will not accomplish anything; tabs and spaces have already been removed by awk (and if they hadn't been, they would have been by the field splitting of the results of the ls|awk command substitution).

Even if all of the above is as intended, the unquoted [:space:] is a bug. It is a valid sh pathname pattern, so, if there is a file in the current directory named 's', or 'p', or 'a', or 'c', or 'e', or ':', tr will never see '[:space:]', but instead the single character with which the shell globbing mechanism replaced it.

Again, not sure what you're trying to do, but that line of shell script is beyond wacky.

Regards,
Alister