[SOLVED] tee disables grep

Andy_CH · 08-14-2014, 01:50 PM

I've a problem with tee

cat /dev/ttyS0 | grep abc

generates exactly that what I want

cat /dev/ttyS0 | grep abc | tee logfile

Writes all lines coming from ttyS0 to the logfile.
What's wrong?

Thanks
Andy

szboardstretcher · 08-14-2014, 01:53 PM

Well, that IS what you are asking it to do...

The question is, what is it you WANT it to do?

Andy_CH · 08-19-2014, 03:34 AM

Hm - I thougt it's clear :-) Sorry

cat /dev/ttyS0 | grep abc

Gives me the output to the console -> exactly as I expect

cat /dev/ttyS0 | grep abc > logfile

Writes it to a file -> exactly as I expect

Now I want to have it in a file and on the console

But using tee, I have much more output than before

(English is definitly not my native language - I hope you understand what I mean)

rupertwh · 08-21-2014, 06:46 AM

You were actually pretty clear the first time around. And what you describe sounds impossible.

My best guess is that you are accidently not looking at the same logfile you are writing to. Or that you are looking at "old" stuff in the logfile while current content is still buffered and not written to the file yet.

Console 1:

Code:

rw@jodel:~$ cat > fifo
Hello
this line shouldn't show
Jelly
rw@jodel:~$

Console 2:

Code:

rw@jodel:~$ cat fifo | grep ll | tee log
Hello
Jelly
rw@jodel:~$ cat log
Hello
Jelly
rw@jodel:~$

Andy_CH · 08-23-2014, 06:49 AM

After a couple of trials I have the idea, that my problem may have to do with the separator ...

cat /dev/ttyS0 > log_1
cat log_1

shows me ^M after each alpha-numeric field.

0F0509F4^M0F0608D7^M0F1E0BFF^M[BatteryManagement] Neuer Zustand: POWER_FAIL
1005FFF8^M100800000005^M070252A37B53

Only after the line starting with [BatteryManagement] (which I terminate with \n in the C-program) a new line starts.

Is there a way to handle that in my command sequence?

[Edit]
Solved!

As I thougt it was not a problem of tee itself

sudo cat /dev/ttyS0 | sed 's/\r/\n/g' | grep -i battery