The Right Way of Running External Commands on Vim

Today I was struggled with one of the worst behavior of Vim script.

Try the following code on your Vim.

:!echo "#!"

Assuming you know that the command :! is to run the given command on your shell. This looks equivalent to

$ echo "#!"

on your terminal.

But Vim will show a cryptic error. That's because both # and ! are special letters for :! command.

• ! is the command previously ran. This is for the pseudo command :!! which means that running the same command again.
• # is the filename previously you edited.
• Similar in %

They may be useful for using Vim, but they make Vim script programmers crazy.