I'm trying to pipe output from echo into a command using GLib's spawn_command_line_sync method. The problem I've run into is echo is interpreting the entire command as the argument.
To better explain, I run this in my code:
string command = "echo \"" + some_var + "\" | command";
Process.spawn_command_line_sync (command.escape (),
out r, out e, out s);
I would expect the variable to be echoed to the pipe and the command run with the data piped, however when I check on the result it's just echoing everything after echo like this:
"some_var's value" | command
I think I could just use the Posix class to run the command but I like having the result, error and status values to listen to that the spawn_command_line_sync method provides.
The problem is that you are providing shell syntax to what is essentially the kernel’s exec() syscall. The shell pipe operator redirects the stdout of one process to the stdin of the next. To implement that using Vala, you need to get the file descriptor for the stdin of the command process which you’re running, and write some_var to it manually.