Unix – Unix utility to prepend timestamps to stdin


I ended up writing a quick little script for this in Python, but I was wondering if there was a utility you could feed text into which would prepend each line with some text — in my specific case, a timestamp. Ideally, the use would be something like:

cat somefile.txt | prepend-timestamp

(Before you answer sed, I tried this:

cat somefile.txt | sed "s/^/`date`/"

But that only evaluates the date command once when sed is executed, so the same timestamp is incorrectly prepended to each line.)

Best Answer

ts from moreutils will prepend a timestamp to every line of input you give it. You can format it using strftime too.

$ echo 'foo bar baz' | ts
Mar 21 18:07:28 foo bar baz
$ echo 'blah blah blah' | ts '%F %T'
2012-03-21 18:07:30 blah blah blah

To install it:

sudo apt-get install moreutils