ls -l not equivalent to
ls < some_params.txt where
some_params.txt would contain
Because the command line isn't the standard input!
ls is not a very good example here, since it doesn't use standard input. It just processes the command line options it gets, looks through some directories, and prints a listing to standard output.
But consider something like
cat -n. It takes the
-n flag from the command line, then reads from its standard input, adds line numbers and prints to standard output. Without
< filename, the input comes from the terminal (i.e. your keyboard). With it, it comes from a file.
What you could do is use command substitution to insert the contents of a file to the command line.
ls $(cat some_params.txt) (or
ls $(< some_params.txt) in shells that support it) would do what you propose.