Monitor a file with tail with timestamps added

tail -f file | while read line; do echo -n $(date -u -Ins); echo -e "\t$line"; done
This is useful when watching a log file that does not contain timestamps itself. If the file already has content when starting the command, the first lines will have the "wrong" timestamp when the command was started and not when the lines were originally written.

6
By: hfs
2010-11-19 10:01:57

3 Alternatives + Submit Alt

What Others Think

Where did you find -I switch? I don't see it in man date ...
depesz · 417 weeks ago
Mmh, I don't remember. It's not listed in my man page, either. It seems to be the short form of '--rfc-3339='.
hfs · 416 weeks and 6 days ago
Could be written with a single echo and without the 'line' variable tail -f file | while read; do echo -e "$(date -u -Ins)\t$REPLY"; done
frans · 416 weeks and 4 days ago
-I is for ISO8601 http://en.wikipedia.org/wiki/ISO_8601 But I don't know what the ns TIMESPEC would be..
derekschrock · 416 weeks and 2 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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