How to send strings/commands to stdin - vala

Question

While testing programs it would be nice to be able to pump strings into stdin for processing (libvala-0.36 on VSCode 1.15.0-insider/Linux Mint 18.2). Below is just for illustration, but stdin.puts/stdin.flush doesn't seem to work. How can I pump keystrokes/strings into stdin?
private void test_func(){
...do stuff
stdin.puts("""{"event":"server.connected","params":{"version":"0.0.1","pid":0}}""");
...do stuff
stdin.puts("exit\r\n");
}
public static int main (string[] args) {
string line;
...do stuff
#if DEBUG
test_func();
#endif
while ((line = stdin.read_line ()) != null) {
line = line.strip ();
if (line.length > 0) {
if (line == "exit") break;
gJsonRPC.handle_request (line);
}
}
...do stuff
}
Update:
Have not found functionality similar to .Net "SendKeys" class in GLib, so temporarily settled on this method....
public static void SendKeys(string sKeys) {
//--------------------------------------------------------------
//OSS:Hack:SendKeys
//--------------------------------------------------------------
char[] _keys = sKeys.to_utf8();
for (int i = _keys.length; i >= 0; i--)
stdin.ungetc (_keys[i]);
//--------------------------------------------------------------
}
#Lasall suggested FileStream.open(¨/dev/stdin¨, ¨w¨), so I try that next.

Answer 1

GLib.stdin really is just a GLib.FileStream.
You can encapsulate your processing code in a function that takes a FileStream like this:
public void my_processing_func (FileStream stream) {
while ((line = stream.read_line ()) != null) {
line = line.strip ();
if (line.length > 0) {
if (line == "exit") break;
gJsonRPC.handle_request (line);
}
}
}
}
Then in your main you can conditionally use either your test data or stdin:
#ifdef DEBUG
var stream = test_func ();
#else
var stream = stdin;
#endif
my_processing_func (stream);
I probably wouldn't use DEBUG, but some more descriptive name like TEST_DATA, also it might be better to use proper unit testing and write a test program instead of #ifdefing your main program.