Add timestamp to cat output from shell script

Question

I have a small script that cats the output from the ttyUSB to a file I would like to prepend a timestamp to each line. From the command line this does everything I want:

$ cat /dev/ttyUSB0 /home/pi/daily_logs/ttyUSSB0 | awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }

My issue is that when I add it to a script everything works but the awk timestamp isn't added. My script line looks like this:

cat < /dev/ttyUSB0 > /home/pi/daily_logs/ttyUSB0 | awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; } &

Any help getting this going would be appreciated.

You might find my `timer` command useful: https://github.com/Keith-S-Thompson/kst-time-utils — Keith Thompson, Jan 04 '13 at 19:04

score 8 · Accepted Answer · edited Apr 13 '17 at 12:36

8

You need to redirect awk's output to the file, not cat's. The way you have it, awk gets nothing. Actually, you may not need cat at all:

awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }' /dev/ttyUSB0 > /home/pi/daily_logs/ttyUSB0 &

edited Apr 13 '17 at 12:36

Community

1
1

answered Jan 04 '13 at 17:14

PleaseStand

31,641
6
68
95

Happy to push you over ;-) Good luck to all. – shellter Jan 04 '13 at 17:52
Awesome thank you, I have a lot more reading to do. Follow up question. Now that I have this running without cat, how to I stop it if I want to roll the file over at end of the day? Currently I am looking for the cat pids st – Argus Jan 07 '13 at 16:58

score 1 · Answer 2 · edited Nov 06 '18 at 15:57

1

You need to put the > /home/pi/daily_logs/ttyUSB0 after the pipe. Like so:

cat < /dev/ttyUSB0 | awk '{ print strftime("%Y-%m-%d %H:%M:%S"), $0; }' > /home/pi/daily_logs/ttyUSB0

edited Nov 06 '18 at 15:57

kkonrad

1,262
13
32

answered Jan 04 '13 at 17:16

Kevin Beck

2,394
2
15
27

score 0 · Answer 3 · answered Jan 04 '13 at 19:03

0

Useless use of cat is impeding the solution. To minimize the changes needed, you can also do:

< /dev/ttyUSB0 > /home/pi/daily_logs/ttyUSB0 awk '...' &

answered Jan 04 '13 at 19:03

William Pursell

204,365
48
270
300

Add timestamp to cat output from shell script

3 Answers3

Linked