Linux Commands Examples

A great documentation place for Linux commands


attach a line discipline to a serial line

see also : inputattach


ldattach [-dhV78neo12] [-s speed] [-i iflag] ldisc device

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The ldattach daemon opens the specified device file (which should refer to a serial device) and attaches the line discipline ldisc to it for processing of the sent and/or received data. It then goes into the background keeping the device open so that the line discipline stays loaded.

The line discipline ldisc may be specified either by name or by number.

In order to detach the line discipline, kill(1) the ldattach process.

With no arguments, ldattach prints usage information.


-d | --debug

Causes ldattach to stay in the foreground so that it can be interrupted or debugged, and to print verbose messages about its progress to the standard error output.

-h | --help

Prints a usage message and exits.

-V | --version

Prints the program version.

-s value | --speed value

Set the speed of the serial line to the specified value.

-7 | --sevenbits

Sets the character size of the serial line to 7 bits.

-8 | --eightbits

Sets the character size of the serial line to 8 bits.

-n | --noparity

Sets the parity of the serial line to none.

-e | --evenparity

Sets the parity of the serial line to even.

-o | --oddparity

Sets the parity of the serial line to odd.

-1 | --onestopbit

Sets the number of stop bits of the serial line to one.

-2 | --twostopbits

Sets the number of stop bits of the serial line to two.

-i value | --iflag [-]value{,...}

Sets the specified bits in the c_iflag word of the serial line. Value may be a number or a symbolic name. If value is prefixed by a minus sign, clear the specified bits instead. Several comma separated values may be given in order to set and clear multiple bits.


The ldattach command is part of the util-linux package and is available from

line disciplines

Depending on the kernel release, the following line disciplines are supported:


The default line discipline, providing transparent operation (raw mode) as well as the habitual terminal line editing capabilities (cooked mode).


Serial Line IP (SLIP) protocol processor for transmitting TCP/IP packets over serial lines.


Device driver for RS232 connected pointing devices (serial mice).


Point to Point Protocol (PPP) processor for transmitting network packets over serial lines.



Line driver for transmitting X.25 packets over asynchronous serial lines.


Driver for Simatic R3964 module.


Linux IrDa (infrared data transmission) driver - see


Synchronous HDLC driver.


Synchronous PPP driver.


Bluetooth HCI UART driver.


Driver for Siemens Gigaset M101 serial DECT adapter.


Driver for serial line Pulse Per Second (PPS) source.

see also

inputattach , ttys


Tilman Schmidt (tilman[:at:]imap[:dot:]cc)

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