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329
ViewsHow to add timestamp while redirecting stdout to file in Bash?
I have a program (server) and I am looking for a way (script) that will redirect (or better duplicate) all its stdout to file and add timestamp for each entry.
I've done some research and the furthest I could get was thanks to How to add timestamp to STDERR redirection. It redirects stdout but the timestamp added is of the time when the script finishes:
#!/bin/bash
./server | ./predate.sh > log.txt
code of predate.sh:
#!/bin/bash
while read line ; do
echo "$(date): ${line}"
done
It seems that server output is flushed after exit of the program.(without redirecting it works fine). Also if I try using predate.sh on given example in mentioned thread, it works perfectly. I am aware it would be easy adding a timestamp to the main program but I would rather avoid editing its code.
3 answers
Answer question0
I recently needed exactly that: receive log messages in a serial console (picocom), print them to a terminal and to a file AND prepend the date.
What I now use looks s.th. like this:
picocom -b 115200 /dev/tty.usbserial-1a122C | awk '{ print strftime("%s: "), $0; fflush(); }' | tee serial.txt
- the output of
picocomis piped toawk awkprepends the date (the%soption converts the time to the Number of seconds since 1970-01-01 00:00:00 UTC - or use%cfor a human-readable format)fflush()flushes any buffered output inawk- that is piped to
teewhich diverts it to a file. (you can find some stuff aboutteehere)
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moreutils ts
Absolute date and time is the default:
$ sudo apt-get install moreutils
$ (echo a;sleep 1;echo b;sleep 3;echo c;sleep 2;echo d;sleep 1) | ts | tee myfile
$ cat myfile
Apr 13 03:10:44 a
Apr 13 03:10:45 b
Apr 13 03:10:48 c
Apr 13 03:10:50 d
or counting from program start with ts -s:
$ (echo a; sleep 1; echo b; sleep 3; echo c; sleep 2; echo d; sleep 1) | ts -s
00:00:00 a
00:00:01 b
00:00:04 c
00:00:06 d
or deltas for benchmarking with ts -i:
$ (echo a; sleep 1; echo b; sleep 3; echo c; sleep 2; echo d; sleep 1) | ts -i
00:00:00 a
00:00:01 b
00:00:03 c
00:00:02 d
$ (echo a; sleep 1; echo b; sleep 3; echo c; sleep 2; echo d; sleep 1) | ts -i '%.s'
0.000010 a
0.983308 b
3.001129 c
2.001120 d
Tested on Ubuntu 18.04, moreutils 0.60.
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For Me Your Code is working perfectly fine
Check this is what I tried
test.sh
#!/bin/bash
while true; do
echo "hello"
done
predate.sh
#!/bin/bash
while read line; do
echo $(date) ":" $line;
done
then
./test.sh | ./predate.sh
gives me
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
Tue Jan 14 17:49:47 IST 2014 : hello
This can be redirected to some file using ">" or ">>" for append
