Active11 months ago
Linux Serial Port
What is the proper way to get a list of all available serial ports/devices on a Linux system?
Moving the License Server of ABBYY FineReader. This article explains how to move the License Server of ABBYY FineReader. Setserial - get/set Linux serial port information Synopsis setserial. A Linux serial port test program. Below is a Linux serial test program which requires the command parameters to be entered on the command line when the.
In other words, when I iterate over all devices in
/dev/
, how do I tell which ones are serial ports in the classic way, that is, those usually supporting baud rates and RTS/CTS flow control?The solution would be coded in C.
I ask because I am using a third-party library that does this clearly wrong: It appears to only iterate over
/dev/ttyS*
. The problem is that there are, for instance, serial ports over USB (provided by USB-RS232 adapters), and those are listed under /dev/ttyUSB*. And reading the Serial-HOWTO at Linux.org, I get the idea that there'll be other name spaces as well, as time comes.So I need to find the official way to detect serial devices. The problem is that none appears to be documented, or I can't find it.
I imagine one way would be to open all files from
/dev/tty*
and call a specific ioctl()
on them that is only available on serial devices. Would that be a good solution, though?Update
hrickards suggested to look at the source for 'setserial'.Its code does exactly what I had in mind:
First, it opens a device with:
Then it invokes:
If that call returns no error, then it's a serial device, apparently.
I found similar code in Serial Programming/termios, which suggested to also add the
O_NOCTTY
option.There is one problem with this approach, though:
When I tested this code on BSD Unix (that is, Mac OS X), it worked as well. However, serial devices that are provided through Bluetooth cause the system (driver) to try to connect to the Bluetooth device, which takes a while before it'll return with a timeout error. This is caused by just opening the device. And I can imagine that similar things can happen on Linux as well - ideally, I should not need to open the device to figure out its type. I wonder if there's also a way to invoke
ioctl
functions without an open, or open a device in a way that it does not cause connections to be made?What should I do?
Thomas Tempelmann
Thomas TempelmannThomas Tempelmann![Abbyy Linux Serial Port Abbyy Linux Serial Port](https://www.rasppishop.de/media/image/product/7258/lg/gpio-zu-serieller-uart-port-max232-fuer-raspberry-pi~4.jpg)
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11 Answers
The
/sys
filesystem should contain plenty information for your quest. My system (2.6.32-40-generic #87-Ubuntu) suggests:Which gives you descriptions of all TTY devices known to the system. A trimmed down example:
Following one of these links:
Here the
dev
file contains this information:This is the major/minor node. These can be searched in the
/dev
directory to get user-friendly names:The
A.H.A.H./sys/class/tty
dir contains all TTY devices but you might want to exclude those pesky virtual terminals and pseudo terminals. I suggest you examine only those which have a device/driver
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In recent kernels (not sure since when) you can list the contents of /dev/serial to get a list of the serial ports on your system. They are actually symlinks pointing to the correct /dev/ node:
This is a USB-Serial adapter, as you can see. Note that when there are no serial ports on the system, the /dev/serial/ directory does not exists. Hope this helps :).
flu0flu0
I'm doing something like the following code. It works for USB-devices and also the stupid serial8250-devuices that we all have 30 of - but only a couple of them realy works.
Basically I use concept from previous answers. First enumerate all tty-devices in /sys/class/tty/. Devices that does not contain a /device subdir is filtered away. /sys/class/tty/console is such a device. Then the devices actually containing a devices in then accepted as valid serial-port depending on the target of the driver-symlink fx.
and for ttyS0
All drivers driven by serial8250 must be probes using the previously mentioned ioctl.
Only port reporting a valid device-type is valid.
The complete source for enumerating the serialports looks like this. Additions are welcome.
Søren HolmSøren Holm
I think I found the answer in my kernel source documentation:/usr/src/linux-2.6.37-rc3/Documentation/filesystems/proc.txt
Here is a link to this file:http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=blob_plain;f=Documentation/filesystems/proc.txt;hb=e8883f8057c0f7c9950fa9f20568f37bfa62f34a
mk2mk2
user6655984
RealHuman75RealHuman75
setserial with the -g option appears to do what you want and the C source is available at http://www.koders.com/c/fid39344DABD14604E70DF1B8FEA7D920A94AF78BF8.aspx.
hrickardshrickards5812 gold badges6 silver badges20 bronze badges
I have no serial device here to test it, but if you have python and dbus you can try it yourself.
If it fails you can search inside
hwmanager_i.GetAllDevicesWithProperties()
to see if the capability name 'serial' that I just guessed has a different name.HTH
baolbaol
I do not have a USB serial device, but there must be a way to find the real ports using the HAL libraries directly:
The posted python-dbus code nor this sh script lists the bluetooth /dev/rfcomm* devices, so it is not the best solution.
Note that on other unix platforms, the serial ports are not named ttyS? and even in linux, some serial cards allow you to name the devices. Assuming a pattern in the serial devices names is wrong.
kelk1kelk1
Using /proc/tty/drivers only indicates which tty drivers are loaded. If you're looking for a list of the serial ports check out /dev/serial, it will have two subdirectories: by-id and by-path.
EX:
Thanks to this post: https://superuser.com/questions/131044/how-do-i-know-which-dev-ttys-is-my-serial-port
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blarfblarf
Linux Serial Port Software
My approach via group dialout to get every tty with user 'dialout'
ls -l /dev/tty* | grep 'dialout'
to only get its folderls -l /dev/tty* | grep 'dialout' | rev | cut -d ' ' -f1 | rev
easy listen to the tty output e.g. when arduino serial out:
head --lines 1 < /dev/ttyUSB0
listen to every tty out for one line only:
for i in $(ls -l /dev/tty* | grep 'dialout' | rev | cut -d ' ' -f1 | rev); do head --lines 1 < $i; done
I really like the approach via looking for drivers:
ll /sys/class/tty/*/device/driver
Linux Serial Port Monitor
You can pick the tty-Name now:
ls /sys/class/tty/*/device/driver | grep 'driver' | cut -d '/' -f 5
Abbyy Linux Serial Portfolio
McPepprMcPeppr
The serial communication manager library has many API and features targeted for the task you want. If the device is a USB-UART its VID/PID can be used. If the device is BT-SPP than platform specific APIs can be used. Take a look at this project for serial port programming: https://github.com/RishiGupta12/serial-communication-manager
samuel05051980samuel05051980