shuf and fmt command

With the shuf command you can shuffle the contents of a file.
$ cat file.txt
file1
file2
file3
file4
file5

$ shuf file.txt
file2
file3
file1
file5
file4

A file with the contents:

abc
def
fgh
ijk

becomes with this command:
$ fmt file.txt
abc def fgh ijk