Bash – Shell script wrapper to prevent running command with no arguments

Well, "$@" expands to the list of positional parameters, one argument per positional parameter.

When you do:

set '' 'foo bar' $'blah\nblah'
cmd "$@"

cmd is being invoked with those 3 arguments: the empty string, foo bar and blah<newline>blah. The shell will call the execve() system call with something like:

execve("/path/to/cmd", ["cmd", "", "foo bar", "blah\nblah"], [envvars...]);

If you want to reconstruct a shell command line (that is code in the shell language) that would reproduce that same invocation, you could do something like:

awk -v q="'" '
  function shellquote(s) {
    gsub(q, q "\\" q q, s)
    return q s q
  }
  BEGIN {
    for (i = 1; i < ARGC; i++) {
      printf "%s", sep shellquote(ARGV[i])
      sep = " "
    }
    printf "\n"
  }' cmd "$@"

Or with zsh, asking for different types of quotes:

$ set '' 'foo bar' $'blah\nblah'
$ print -r -- cmd "${(q)@}"
cmd '' foo\ bar blah$'\n'blah
$ print -r -- cmd "${(qq)@}"
cmd '' 'foo bar' 'blah
blah'
$ print -r -- cmd "${(qqq)@}"
cmd "" "foo bar" "blah
blah"
$ print -r -- cmd "${(qqqq)@}"
cmd $'' $'foo bar' $'blah\nblah'

Or with zsh, bash or ksh93 (here for bash, YMMV with other shells):

$ set '' 'foo bar' $'blah\nblah'
$ printf cmd; printf ' %q' "$@"; printf '\n'
cmd '' foo\ bar $'blah\nblah'

You could also use the shell's xtrace option that causes the shell to print what it's going to execute:

$ (PS4=; set -x; : cmd "$@")
: cmd '' 'foo bar' 'blah
blah'

Above, we ran the : no-op command with cmd and the positional parameters as argument. My shell printed them in a nice quoted fashion suitable for reinput to the shell. Not all shells do that.

Conveniently, xargs -I does exactly what you want:

$ xargs <my_file_list.txt -I filename ./my_command "filename"

-I replace-str
    Replace occurrences of replace-str in the initial-arguments with names read
    from standard input.
    Also, unquoted blanks do not terminate input items;
    instead the separator is the newline character.
    Implies -x and -L 1.

This means it takes exactly one newline-delimited input line and invokes your command with it as a single argument. Nothing apart from newline is treated as a delimiter, so spaces and other special characters are fine.

Note that if you wanted to allow newlines in your filenames, the nul terminator (as per Wildcard's answer) will also work in a file.