Listen to a background process in vala - vala

Question

I have a command I want to listen to in the background Process.spawn_command_line_async is what I want but I can't work out how to then listen to the response. The command will output lines when something needs updating and I then need to parse that line and run a function accordingly. The process won't end until stopped, so will need to be listened to as it's running.

Answer 1

What you want is Process.spawn_commandline_async_with_pipes (). Valadoc has a code example:
private static bool process_line (IOChannel channel, IOCondition condition, string stream_name) {
if (condition == IOCondition.HUP) {
print ("%s: The fd has been closed.\n", stream_name);
return false;
}
try {
string line;
channel.read_line (out line, null, null);
print ("%s: %s", stream_name, line);
} catch (IOChannelError e) {
print ("%s: IOChannelError: %s\n", stream_name, e.message);
return false;
} catch (ConvertError e) {
print ("%s: ConvertError: %s\n", stream_name, e.message);
return false;
}
return true;
}
public static int main (string[] args) {
MainLoop loop = new MainLoop ();
try {
string[] spawn_args = {"ls", "-l", "-h"};
string[] spawn_env = Environ.get ();
Pid child_pid;
int standard_input;
int standard_output;
int standard_error;
Process.spawn_async_with_pipes ("/",
spawn_args,
spawn_env,
SpawnFlags.SEARCH_PATH | SpawnFlags.DO_NOT_REAP_CHILD,
null,
out child_pid,
out standard_input,
out standard_output,
out standard_error);
// stdout:
IOChannel output = new IOChannel.unix_new (standard_output);
output.add_watch (IOCondition.IN | IOCondition.HUP, (channel, condition) => {
return process_line (channel, condition, "stdout");
});
// stderr:
IOChannel error = new IOChannel.unix_new (standard_error);
error.add_watch (IOCondition.IN | IOCondition.HUP, (channel, condition) => {
return process_line (channel, condition, "stderr");
});
ChildWatch.add (child_pid, (pid, status) => {
// Triggered when the child indicated by child_pid exits
Process.close_pid (pid);
loop.quit ();
});
loop.run ();
} catch (SpawnError e) {
print ("Error: %s\n", e.message);
}
return 0;
}
valac --pkg glib-2.0 GLib.Process.spawn_async_with_pipes.vala