How to redirect the output of a command as the quickfix list to a vim server / function?

Question

When I click on a link in thunderbird and firefox is already running, it doesn't open a new window, just a new tab.

I want the same thing for vim: no matter where I am and how I send a bunch of files to it, I want them opened in a single session.

To do this, I've added the following code in my ~/.bashrc and ~/.zshrc.

function nv {

vim --serverlist | grep -q VIM

if [ $? -eq 0 ]; then

    if [ $# -eq 0 ]; then
        vim
    else
        vim --remote "$@"
    fi

else
    vim --servername vim "$@"
fi

}

It defines the function nv which can do 3 things :

• if no VIM server is running, nv launches one
• if a VIM server is running and one or more arguments were passed to nv, it sends them to the server
• if a VIM server is running but no argument was passed to nv, it launches a simple vim session (so that I can still launch a separate vim session by using the same function / alias)

---

I've recently read that you could redirect the output of a shell command as the quickfix list to vim. For example :

vim -q <(grep -Rn foo *)

It works with vim but not with my function nv.

I would like to use the same syntax so that the output of grep is not opened by a new vim session, but by the VIM server.

When I use nv -q <(grep -Rn foo *), the VIM server doesn't receive the output of grep but a file called -q and another one : /proc/<pid>/fd/11.

I know why it doesn't work, the function was not written with that case in mind.

But then, I tried something simpler : vim --remote -q <(grep -Rn foo *)

And the result is the same, it doesn't work, the server still receives two files : -q and /proc/<pid>/fd/11.

I would like to know if it's possible to edit the code of my nv function so that it works when I use it with the -q switch to remotely populate the quickfix list of an already running vim server, and if so receive some advice on how to do it.

If it's not, at least, I would like to know how to use the -q and --remote switch simultaneously.

---

Edit : I may be wrong but I don't think -q and --remote can be used simultaneously.

For the moment, I've come up with the following command :

vim --remote-send ":grep -Rn foo *<cr><cr>"

Now I need to edit the nv function to integrate it, but I don't know how to do it.

Edit bis: I don't think it's worth the trouble, I'll stick with nv and the last command when needed.

Answer 1

You cannot use --remote with -q, any arguments after --remote are treated as filenames:

--remote    Connect to a Vim server and make it edit the files given in
            the rest of the arguments.  If no server is found a warning
            is given and the files are edited in the current Vim.

That said, you cannot use the result of process substitution (<(cmd)) with a program running elsewhere. If you notice, the file name from process substitution uses /proc/self:

$ echo <(date)
/proc/self/fd/11

The shell sets up the file descriptors of the executed command so that one of them points the substituted process. Naturally, this fd cannot be easily used by a separate process - you'll at least need to translate /proc/self to /proc/<PID>.

Therefore, it would be easier if we could run the command in Vim itself. The cexpr command should help us there: quickfix.txt For Vim version 7.4. Last change: 2015 Sep 08

                                                        :cex :cexpr E777
:cex[pr][!] {expr}      Create a quickfix list using the result of {expr} and
                        jump to the first error.
                        If {expr} is a String, then each new-line terminated
                        line in the String is processed using the global value
                        of 'errorformat' and the result is added to the
                        quickfix list.
                        If {expr} is a List, then each String item in the list
                        is processed and added to the quickfix list.  Non
                        String items in the List are ignored.
                        See :cc for [!].
                        Examples: 
                                :cexpr system('grep -n xyz *')
                                :cexpr getline(1, '$')

Huh, one of the examples uses grep much the same way you do.

Using cexpr, the following function could work:

function nv (
    if vim --serverlist | grep -q VIM; then
        if [ $# -eq 0 ]; then
            vim
        elif [[ $1 == -q ]]; then
            shift
            IFS=' '
            vim --remote-send ":cexpr system('$*')<cr><cr>"
        else
            vim --remote "$@"
        fi
    else
        vim --servername VIM "$@"
    fi
)

Use it thus:

nv -q grep -Rn foo *

That's to say, you pass the command as you would write it to nv -q. The function checks if the first argument is -q, and then uses vim --remote-send to call cexpr and system() on the rest of the arguments.

This bit might need explaining:

shift
IFS=' '
... system('$*') ...

Since the first argument is -q and it's no longer needed, and using $* is more convenient, I simply discard -q.

Now, there are two quick ways of combining the arguments: $@ and $*. A quoted $@ is usually preferred, if you want separate words (we don't). So, we use $*, which combines the arguments using the first character of IFS. What the value of IFS is depends on the shell, so I set it to a space to get the needed effect.

The best effect is if you send a quoted command:

nv -q 'grep -Rn foo *'

Then * won't be expanded by the shell you called it from, thus preventing problems when called by system().

Note

My earlier version of the function used {} to group the command. This version uses (), to create a subshell. This makes it easier to set variables like IFS locally without disturbing the shell.