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I'd like to add a functionality to a project I'm working on, in which as soon as an external controller device powers on, it sends a time-request/command to a ttyusb port of an Ubuntu PC, and the Ubuntu PC sends back the system's time and date. Does such a command exists in Ubuntu?

for example something like:

'timeReq' > /dev/ttyUSB0

In which "time" is the command that would echo back the system's time

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  • Does this answer your question? How do I connect to TTY/COM (/dev/ttyUSB0)?
    – K7AAY
    Mar 12, 2020 at 17:29
  • @K7AAY Not really, I'm specifically asking about a special command that would echo back the time and date on my Ubuntu system. The answer you have provided is just to interact with the ttyUSBxx port. But thank you
    – Marco Castro
    Mar 12, 2020 at 17:34
  • You probably think that you can redirect only echo output. That is wrong.
    – Pilot6
    Mar 12, 2020 at 17:48
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    Does the edit to the question explain better what you're looking for?
    – K7AAY
    Mar 12, 2020 at 18:06
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    No: Allowing random external devices without login to issue shell commands would be a tremendous security hole. Imagine all the damage a nefarious USB device could cause!
    – user535733
    Mar 12, 2020 at 21:14

1 Answer 1

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The command that outputs system time is date.

You can use format parameters to output only the time.

Also you can send its output to USB using > redirection.

Example

date +%R > /dev/ttyUSB0

The user needs to be a mamber of dialout group or have some other permissions to be able to write there.

You can use man date to see for other formatting options.

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  • Just to clarify, If I send "date +%R > /dev/ttyUSB0" as a string from my embedded device to the ttyUSB0 port, will Ubuntu recognize that as a shell command and then send the result back to the USB0 port?
    – Marco Castro
    Mar 12, 2020 at 17:53
  • I don't know what you mean by "sending back to USB port". This command in Ubuntu will send time to USB port. Everything else about some embedded device is uclear.
    – Pilot6
    Mar 12, 2020 at 17:55
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    What I mean is, if you write that command (date +%R > /dev/ttyUSB0) in your terminal, it will send the time to the USB port correct? but what I intend is to ask for the time from the embedded device. "a time request" to put it on other words
    – Marco Castro
    Mar 12, 2020 at 18:02
  • Yes, it is correct. You can try yourself and see what this command deoes without redirection.
    – Pilot6
    Mar 12, 2020 at 18:11

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