Read serial input with awk, insert date

Question

I'm trying to reformat serial input, which consists of two integers separated by a comma (sent from an Arduino):

1,2
3,4
0,0
0,1

etc. I would like to append the date after each line, separating everything with a tab character. Here's my code so far:

cat /dev/cu.usbmodem3d11 | awk 'BEGIN {RS=","};{printf "%i\t%i\t%s",$1,$2,system("date")}'

Here's the result I get (with date in my locale):

1   2   0Mer 26 fév 2014 22:09:20 EST
3   4   0Mer 26 fév 2014 22:09:20 EST
0   0   0Mer 26 fév 2014 22:09:20 EST
0   1   0Mer 26 fév 2014 22:09:20 EST

Why is there an extra '0' in front of my date field? Sorry for the newbie question :(

EDIT This code solved my problem. Thanks to all who helped.

awk 'BEGIN {FS=","};{system("date")|getline myDate;printf "%i\t%i\t%s",$1, $2, myDate}' /dev/cu.usbmodem3d11

I'm not clear why, but in order for the date to keep updating and recording at what time the data was received, I have to use system("date")instead of just "date"in the code above.

Answer 1

2 things

It will be easier to see your problem if you add a \n at the end of your printf string

Then the output is

>echo '1,2' | awk 'BEGIN {RS=","};{printf "%i\t%i\t%s\n",$1,$2,system("date")}'
Wed Feb 26 21:30:17 CST 2014
1       0       0
Wed Feb 26 21:30:17 CST 2014
2       0       0

I'm guessing that output from system("date") returns its output "outside" of scope of awk's $0 natural scope of each line of input processed. Others may be able to offer a better explanation.

To get the output you want, I'm using the getline function to capture the output of the date command to a variable (myDt). Now the output is

> echo '1,2' | awk 'BEGIN {RS=","};{"date" | getline myDt ; printf "%i\t%i\t%s\n",$1,$2,myDt}'
1       0       Wed Feb 26 21:31:15 CST 2014

2       0       Wed Feb 26 21:31:15 CST 2014

Finally, we remove the "debugging" \n char, and get the output you specify:

> echo '1,2' | awk 'BEGIN {RS=","};{"date" | getline myDt ; printf "%i\t%i\t%s",$1,$2,myDt}'
1       0       Wed Feb 26 21:34:56 CST 2014
2       0       Wed Feb 26 21:34:56 CST 2014

And, per Jaypal's post, I see now that FS="," is another issue, so when we make that change AND return the `\n' char, we have

echo '1,2' | awk 'BEGIN {FS=","};{"date" | getline myDt ; printf "%i\t%i\t%s\n",$1,$2,myDt}'
1       2       Wed Feb 26 21:44:42 CST 2014