Question

I’m trying to use vala to start an external application using GLib with spawn_command_line_sync().
According to the documentation (http://valadoc.org/#!api=glib-2.0/GLib.Process.spawn_sync) you can pass a string to store the output of the external application.

While this works fine when starting a script which prints a couple of lines, I need to call a program which will print the content of a binary file.
(for example “cat /usr/bin/apt-get”)

Is there any way how I can receive the output of the external program not in a string, but in a DataStream or something like that ?

I’m planning to write the ouput of the external program to a file, so just calling “cat /usr/bin/apt-get > outputfile” would be an alternative (not as nice), but it doesn’t seem to work.

Anyway I would prefer it to get some kind of Output Stream.
I would appreciate any help.

Code im using:

using GLib;

static void main(string[] args) {
    string execute = "cat /usr/bin/apt-get";
    string output = "out";

    try {
        GLib.Process.spawn_command_line_sync(execute, out output);
    } catch (SpawnError e) {
        stderr.printf("spawn error!");
        stderr.printf(e.message);
    }

    stdout.printf("Output: %s\n", output);
}

Answer 1

GLib.Process.spawn_async_with_pipes will let you do just that. It spawns the processes and returns a file descriptor for each of stdout, stderr, and stdin. There’s a sample of code in the ValaDoc on how to set up IOChannels to monitor the output.