Ucode - how to get output from binary into an variable

Installing and Using OpenWrt
1

I am trying a little ucode -just for fun.
I would like to execute ping -c 3 127.0.0.1 and capture the output to an variable.
I cannot use system(command, timeoutopt) → {number} since it only outputs exit code.

2

You need to use a ubus.call to execute external programs. Something like this:

#!/usr/bin/ucode -S

import * as mod_ubus from "ubus";
let ubus = mod_ubus.connect();
if (! ubus) {
    warn(`Unable to connect to ubus: ${mod_ubus.error()}\n`);
    exit(1);
}

let cmd = {
    command: "/bin/ping",
    params:  [ "-c4", "google.com" ],
};
let data = ubus.call("file", "exec", cmd);
if (data?.code == 0) {
    printf("stdout = %s\n", data.stdout);
}
else {
    printf("Ping failed: %s\n", data);
}

ubus.disconnect();
exit(0);
2 Likes
3

Thank you. Just what I needed.

Where do I find the documentation for ubus? It is not in https://ucode.mein.io/

4

Oh, now you're asking too much... Documentation? :joy:

I don't think there is any for the ubus module. I learned from seeing a ubus call somewhere (fw4 code???), then dug into the ucode source, starting around here: https://github.com/jow-/ucode/blob/master/lib/ubus.c#L1994

I listed various ubus calls and translated them into the ucode version. There's some pretty useful stuff just in the ubus file object.

$ ubus -v list file
'file' @b0e6aa85
        "read":{"path":"String","base64":"Boolean","ubus_rpc_session":"String"}
        "write":{"path":"String","data":"String","append":"Boolean","mode":"Integer","base64":"Boolean","ubus_rpc_session":"String"}
        "list":{"path":"String","ubus_rpc_session":"String"}
        "stat":{"path":"String","ubus_rpc_session":"String"}
        "md5":{"path":"String","ubus_rpc_session":"String"}
        "remove":{"path":"String","ubus_rpc_session":"String"}
        "exec":{"command":"String","params":"Array","env":"Table","ubus_rpc_session":"String"}

Another good (undocumented) one is the ucode-mod-uclient for doing wget-like stuff, which is how I do web queries in owut, although it's new for 24.10 and not available in earlier versions.

5

Thank you. Now I have an idea of what I could find in ubus.

6

You might also poke through owut, it uses ubus in several places:

https://github.com/efahl/owut/blob/main/files/owut#L968