Is there a Unix utility to prepend timestamps to s

Question

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.)

Answer 1

Here's my awk solution (from a Windows/XP system with MKS Tools installed in the C:\bin directory). It is designed to add the current date and time in the form mm/dd hh:mm to the beginning of each line having fetched that timestamp from the system as each line is read. You could, of course, use the BEGIN pattern to fetch the timestamp once and add that timestamp to each record (all the same). I did this to tag a log file that was being generated to stdout with the timestamp at the time the log message was generated.

/"pattern"/ "C\:\\\\bin\\\\date '+%m/%d %R'" | getline timestamp;
print timestamp, $0;

where "pattern" is a string or regex (without the quotes) to be matched in the input line, and is optional if you wish to match all input lines.

This should work on Linux/UNIX systems as well, just get rid of the C\:\\bin\\ leaving the line

             "date '+%m/%d %R'" | getline timestamp;

This, of course, assumes that the command "date" gets you to the standard Linux/UNIX date display/set command without specific path information (that is, your environment PATH variable is correctly configured).

Answer 2

caerwyn's answer can be run as a subroutine, which would prevent the new processes per line:

timestamp(){
   while read line
      do
         echo `date` $line
      done
}

echo testing 123 |timestamp

Answer 3

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

Answer 4

annotate, available via that link or as annotate-output in the Debian devscripts package.

$ echo -e "a\nb\nc" > lines
$ annotate-output cat lines
17:00:47 I: Started cat lines
17:00:47 O: a
17:00:47 O: b
17:00:47 O: c
17:00:47 I: Finished with exitcode 0

Answer 5

Distilling the given answers to the simplest one possible:

unbuffer $COMMAND | ts

On Ubuntu, they come from the expect-dev and moreutils packages.

sudo apt-get install expect-dev moreutils