Appending Sed Output to a File

humbert

(edited so that the first command makes sense)

I want to parse the input from a tty device and append the output to a file. These are my failed attempts:

sed "s/Temperature/`date +%c`, Temperature/" /dev/ttyFT232 >> /home/temperature.log

and

cat < /dev/ttyFT232 | sed "s/Temperature/`date +%c`, Temperature/" >> /home/temperature.log

I've tried a lot of variations on these themes but those are the gist. I would use the /w flag but I don't want the output file overwritten each time.

I've seen similar examples on other websites which are purported to have worked so I just can't understand it.

PrzemoF

The first one should work - it works for me on android phone, but I used a file as the source.

Have you tried to use a file instead of /dev/ttyXXX?

Is the destination file accesible for writing?

Can you explain "failed"? (error / no result at all / resulet different than expected)

humbert

That's interesting, it does work with a file.

The reason I didn't test it with a file is that when I removed the
>> output_file
the parsed tty input was being printed to the stdout/terminal correctly, so I assumed no problem with reading from the device. The users group has access to the device and I've tested this successfully using cat and grep.

Thanks for the suggestion. Still very odd.

E.g. of output:
cat:
Temperature: 20
Temperature: 21
Temperature: 19

sed "s/Temperature/`date +%c`, Temperature/" /dev/ttyFT232:
14 Mar 2012 18:04:34 Temperature 20
14 Mar 2012 18:04:44 Temperature 21
14 Mar 2012 18:05:24 Temperature 21

Then when I change to
sed "s/Temperature/`date +%c`, Temperature/" /dev/ttyFT232 >> /home/temperature.log
There is no text coming to the stdout but nothing going to the file.

I think I need to test it with more conventional inputs making sure each step works since PrzemoF has shown it's not a problem with the sed command.

PrzemoF

Try mkfifo.
Some examples here: https://en.wikipedia.org/wiki/Mkfifo#Named_pipes_in_Unix