Presently I am getting the weight reported by a large legal for trade scale over the serial port using

The problem is that it seems to be actively updating the screen with the reported weight changes. I intend to create an ajax long polling script that runs every few seconds from apache to check what the current weight on the scale is. The most obviously solution to me is to have the above command continually output the value to a script, continually overwriting it's contents with the latest reported number.

I feel like this should be simple but I don't quite understand why `cat` doesn't terminate like normal when I run it against normal text files.

Any tips in the right direction greatly appreciated.

As I posted in your other thread in my follow up post I suspected the serial port was configured for a remote display which always outputs a reading. Since the serial port outputs continuous data there isn't an EOF or the like so it doesn't terminate. Do you know if serial port has other output modes?

Using cat or bash IMHO usually doesn't work very well with serial ports and using a programming language with serial port support is better.

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It does have other modes, but when I set it to "stabilize" (as in, once the weight has stabilized, it sends a single weight to the serial port, but it never sends back the zero when the weight is removed from the scale, it will only send the next weight greater than zero which is not optimal for my use case).

I am thinking I may want to just run `cat` command for 5 seconds at a time, log that data to a txt file, and then have apache/php read the latest line. A bit jank, was hoping for something a bit more elegant.

I see in the manual for the scale it can be configured to send a "stop bit". Is that something that can send an End Of File? Manual here: https://www.ohaus.ca/pdf/3000-Series-Indicators-Man.pdf (section 3.8 Print Menu)

Memory serves I used to use like tail -f

See sections 5.1 and 5.2, looks like there is a way to poll for data. I am guessing if auto print is off you can send commands.

The stop bit is part of the RS-232 protocol that defines how data is sent.

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Amazing! I never thought I'd be able to send commands to the scale to request data back.

How would I go about (or what should I search for) sending commands and receiving output from this thing?

Something like

?

A suggest a real language because using bash can be unreliable. Using Python should be fairly easy.