Shell Programming and Scripting

I wanna to read the output of various commands like mpstat, vmstat, etc... but want to output this to a file with each line preceeded by a time stamp.

I've played around with various loops, shell redirection, custom descriptors and etc.. but can't seem to get something to work. I did this years ago and know it can be done but my scripting skills have gotten way rusty.

Anyone have any tricks for doing something like this?

Thx

Step 1:
Create a perl script to display the time and the output.

Filename : dispTime.pl

Code:

#!/usr/bin/perl
while (<>) { print localtime() . ": $_"; }

Step2:
chmod 755 dispTime.pl

Step3:
Execute any command and pipe the above perl script. See the output now :-)

ex:
$ vmstat 1 5 | dispTime.pl
Wed Nov 17 10:12:06 2010: kthr memory page disk faults cpu
Wed Nov 17 10:12:06 2010: r b w swap free re mf pi po fr de sr m0 m1 m2 m9 in sy cs us sy id
Wed Nov 17 10:12:06 2010: 0 0 0 18427800 7747944 59 488 47 3 3 0 0 4 3 3 1 479 4262 1344 1 3 96
Wed Nov 17 10:12:07 2010: 0 0 0 9142184 449832 124 200 0 0 0 0 0 0 0 0 0 465 1334 1160 0 2 98
Wed Nov 17 10:12:08 2010: 0 0 0 9142184 449832 4 4 0 0 0 0 0 0 0 0 0 378 935 884 0 1 98
Wed Nov 17 10:12:09 2010: 0 0 0 9142184 449832 4 4 0 0 0 0 0 0 0 0 0 389 1035 889 0 1 98
Wed Nov 17 10:12:10 2010: 0 1 0 9142184 449832 4 4 0 0 0 0 0 1 1 1 0 421 7476 1529 1 10 90

Would you like unix time, gregorian date-time, microseconds, delta microseconds? Simplest with min latency:

Code:

... | while [ 1 ]
 do
   l=`line`
  date '+%whatever'"$l"
 done

Commands that read stdin with a buffered FILE* often get the pipe data several K at a time, delayed. I have found that reading one byte at a time, like line does, overcomes this latency. Commands that write() one line at a time may not have this problem. Your UNIX may vary!