Using `` >'' to redirect output to a file is destructive: in other words, the command
overwrites the contents of the file file-list. If, instead, you redirect with the symbol `` >>'', the output will be appended to the named file, instead of overwriting it.
will append the output of the ls command to file-list.
Just keep in mind that redirection and using pipes are features provided by the shell---the shell provides this handy syntax using `` >'' and `` >>'' and `` |''. It has nothing to do with the commands themselves, but the shell.