Unlock & Lock your mac

lock.m

extern void SACLockScreenImmediate ( );

SACLockScreenImmediate();

unlock.m

io_registry_entry_t r = IORegistryEntryFromPath(kIOMasterPortDefault, "IOService:/IOResources/IODisplayWrangler");
if (r) {
    IORegistryEntrySetCFProperty(r, CFSTR("IORequestIdle"), kCFBooleanFalse);
    IOObjectRelease(r);
}

NSString *pw = [SSKeychain passwordForService:@"login" account:@"login"];

NSString *s = @"tell application \"System Events\"\n\
tell application \"ScreenSaverEngine\" to quit\n\
delay 0.5\n\
keystroke \"%@\"\n\
keystroke return\n\
end tell";

NSDictionary *err;
NSAppleScript *script = [[NSAppleScript alloc] initWithSource:[NSString stringWithFormat:s,pw]];
[script executeAndReturnError:&err];