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Text-Terminals on Linux


13.12 Meaning of Received Control Codes

Auto New Line {Newline}

In this case "New Line" means a new line starting at the left margin below the current line. In Linux and C "new line" (NL) may have a different meaning: the line-feed control character LF also called new-line or NL. This is because in Linux text files, the LF character means a "new line starts here" so it's labeled NL. Normally, a LF (NL) sent to a terminal only results in the cursor jumping down one line below where is was and does not move the cursor back to the start of this "new line".

If Auto New Line is set, the above "normal" situation is canceled and a physical new line is created on the display upon receiving a LF from the host. This is exactly what one wants in Linux. Except that (when Auto New Line is set) the Return (or Enter) key sends a CR LF sequence to the host (for Wyse and VT100, but for VT420 ??). Since Linux uses LF as a "new line" marker in files, Linux would like only a LF to be sent (and not a CR LF). Thus the "New Line" option is seldom used. Instead, the required translations are made by the serial port device driver by default. It is as if one gave the command "stty onlcr icrnl". But you don't need to do this since it's the default.

Auto Line Feed {Rcv CR}

This is just another type of "Auto New Line". When a CR (carriage return) character is received, a LF (line feed) action is added resulting in a new line being displayed. Since Linux marks the end of lines with LF, this option is not used.

Recognize Del (Wyse Only ??) or Null

If off, the DEL character received by the terminal is ignored. If on the DEL performs a destructive backspace. Null characters are usually ignored in any case. Both DEL and NULL are sometimes used for padding. See Padding

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