tcgetpgrp

pub fn tcgetpgrp(handle: fd_t) TermioGetPgrpError!pid_t {
    while (true) {
        var pgrp: pid_t = undefined;
        switch (errno(system.tcgetpgrp(handle, &pgrp))) {
            .SUCCESS => return pgrp,
            .BADF => unreachable,
            .INVAL => unreachable,
            .INTR => continue,
            .NOTTY => return error.NotATerminal,
            else => |err| return unexpectedErrno(err),
        }
    }
}