Create and open file with one command?

If you are looking for some logic for this, ie. create a file and open if possible you could use something like this:

touch testFile && vi testFile

Here testFile is created with touch. The && part says if the creation was successful then open it with vi.

Also, you could just create a new file with something like vi, while opening it at the same time (this assumes you save the file after editing it).

vi testFile

That entirely depends on your text editor. Most will allow you to simply open a non-existent file, and assume you want it created on save.

You could also use a function if that is somehow not possible for you:

cropen() {
    if ! [ "$1" ]; then
        echo "need a file!" >&2
        return 1
    fi
    : > "$1" && open "$1"
}

You can call it as cropen file.

Use vim. Just type

vim newfile.txt

For vim you need to know the hot-keys.

i   - Insert text in the file
esc - return to the command-input-mode
:w  - Write (save)
:q  - Quit (exit)

or (Easier to use Nano):

nano newfile.txt

If you want a GUI type: (Works for ubuntu and other distros)

gedit newfile.txt

Like everyone is telling you, this depends on your editor. And if you don't like the way your editor handles this, that can probably be configured, as well.

With Emacs, emacs new_file.txt (for a nonexistent new_file.txt in the current directory) will bring up Emacs and display a buffer that refers to a new_file.txt. However, until you save, there will be no such file. If you don't do anything and quit, no file will have been created.

While this is certainly one way, I think an even better way is to always have an instance of Emacs running. So, whenever you feel the need for a new file, go to Emacs, hit C-x C-f (or M-x find-file RET), then write the path to the nonexistent file, and you're at the same point as after the CLI command (above, in the second paragraph).