How does vim use the current line as a parameter to execute shell commands?

  question, vim
1 hello
 2 world
 3 me

For example, I am now in the second row, how do I execute it! echo world?

:.w ! commandThe command can send the current line to the standard input of the command, for example:.w ! cat, of course, this does not meet your needs, because you want as a command line argument, so you can use this:
:.w ! xargs command
Well, I know it’s ugly, but it does work …