How do the CLOCAL and CRTSCTS Flags in termios.c_cflag Affect the Serial Port?

Question

I want to configure a UART to use the Hardware Flow Control lines RTS and CTS in Linux. According to http://linux.die.net/man/3/termios, CRTSCTS enables RTS/CTS (hardware) flow control, and CLOCAL configures the serial port to ignore modem control lines. The 2 flags seem contradictory, how can you have hardware flow control enabled with CRTSCTS and ignore the lines with CLOCAL?

Answer 1

CLOCAL ignores only the CD signal.