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I am running the top command to see details about specific processes. The output is piped to grep like so:

top -n 1 | grep jre

The output is usually around 4 lines, and I would like to prefix the current time to each line so it would be something like:


2772 deleteme  20   0  2832 1156  872 R  2.0  0.1   0:00.01 top  


13:46 25-08-2012 2772 deleteme  20   0  2832 1156  872 R  2.0  0.1   0:00.01 top  
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2 Answers

Look at the ts command from the moreutils package:

       ts - timestamp input

       ts [-r] [format]

       ts adds a timestamp to the beginning of each line of input.

You can e.g. use it as such:

$ top -n 1 | grep init | ts
aug 28 17:15:00     1 root      20   0 24448 2272 1340 S    0  0.1   0:01.07 init
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This is so simple! WOW! Why does TS add a empty line between entries? Any way to stop that? –  neildeadman Aug 29 '12 at 8:27
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The ps command is better suited for this kind of task. Try something like this:

$ ps -ao bsdstart,fuser,pid,%cpu,%mem,args | grep jre

From the ps man page:

ps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top(1) instead.

In the command I suggested, the option '-a' tells ps to print processes for all users. The -o specifies the output format. In my example (again from the ps man page):

bsdstart : time the command started.  If the process was
                             started less than 24 hours ago, the output format
                             is " HH:MM", else it is " Mmm:SS" (where Mmm is
                             the three letters of the month).  See also
                             lstart, start, start_time, and stime.

fuser    :  filesystem access user ID.  This will be the
                             textual user ID, if it can be obtained and the
                             field width permits, or a decimal representation
pid      :  a number representing the process ID (alias tgid).

%cpu     :  cpu utilization of the process in "##.#" format.
                             Currently, it is the CPU time used divided by the
                             time the process has been running
                             (cputime/realtime ratio), expressed as a
                             percentage.  It will not add up to 100% unless
                             you are lucky.  (alias pcpu).
%mem     :  ratio of the process's resident set size  to the
                             physical memory on the machine, expressed as a
                             percentage.  (alias pmem).

args     : command with all its arguments as a string.
                             Modifications to the arguments may be shown.  The
                             output in this column may contain spaces.  A
                             process marked <defunct> is partly dead, waiting
                             to be fully destroyed by its parent.  Sometimes
                             the process args will be unavailable; when this
                             happens, ps will instead print the executable
                             name in brackets.  (alias cmd, command).  See
                             also the comm format keyword, the -f option, and
                             the c option.
                             When specified last, this column will extend to
                             the edge of the display.  If ps can not determine
                             display width, as when output is redirected
                             (piped) into a file or another command, the
                             output width is undefined (it may be 80,
                             unlimited, determined by the TERM variable, and
                             so on).  The COLUMNS environment variable or
                             --cols option may be used to exactly determine
                             the width in this case.  The w or -w option may
                             be also be used to adjust width.

You can change this to suit your needs. Have a look at man ps and search for "STANDARD FORMAT SPECIFIERS" (you can use vi-style search in man pages, hit "/" and enter your search pattern, "n" will move to the next match).

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That's perfect! Anyway to include the headers? I realise grep stops this, but anyother way? –  neildeadman Aug 28 '12 at 14:28
Actually, it doesn't work right. if I just ran the top & grep commands together (i.e. without you line) it seems to show more results.... –  neildeadman Aug 28 '12 at 14:33
@neildeadman It will show more lines if you are not using the -n1 option. –  terdon Aug 28 '12 at 14:38
but with the -n 1 and not your additional commands it shows 4 lines, but with your additional lines and the -n 1 it shows 1 line and sometimes 3 or 4. –  neildeadman Aug 28 '12 at 14:41
@neildeadman Another problem is that the output of top is strange. It manipulates the terminal somehow. If you tell me what exactly you need to do (what information do you want from top's headers for example), I should be able to give you a working command using ps. –  terdon Aug 28 '12 at 14:45
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