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I have a prstat log, as you all know the date and time is recorded on the top of the log file, I would like to add that date and time to the begging of each line until it gets to a new date, then I would do the same for that part of the log.

Is this possible?, is there a way to do this through commands or a script, I would've created a script to do so, but it's too late as the data has already been collected.

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up vote 1 down vote accepted

Assuming date format is yyyy-mm-dd hh:mi:ss you can use this perl script:

#!/usr/bin/perl -w

open(FILEH,"<","your.log") or die "cannot open file";
my $date = "0000-00-00 00:00:00";

while(<FILEH>) {
    if( /^([A-Z][a-z]{2}\s[A-Z][a-z]{2}\s[0-9]+\s[0-2][0-9]:[0-5][0-9]:[0-5][0-9]\s[0-9]{4})$/ ) {
        $date = $1;
    else {
        print "$date $_";

Change your.log with full path of your log file.

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I've modified the pattern for date. Which is the full path? – Laurentiu Roescu Dec 13 '12 at 7:27
The regex matched the timestamp in the logs correctly, but for some reason its printing the default 000-00-00 00:00:00 on each line, I cant see why, the perl script is correct by finding the timestamp and printing it when it reaches a line where it doesnt, but I cant find out why its printing the default value only... Adding the full path worked btw – I AM L Dec 13 '12 at 7:34
If it is printing the default I don't think it matches the timestamp correctly. Can you give me a real timestamp example? – Laurentiu Roescu Dec 13 '12 at 7:46
Actually this is my fault, I did not explain my question properly, you see a prstat log has multiple chunks of lines, after another second or so, another chunk is then logged with a new timestamp above it, on top of each chunk looks something like this: ### (1311344015) Thu Dec 13 01:03:35 2012 – I AM L Dec 13 '12 at 7:50
I tested your regex with an online perl regex tester and its matching it perfectly – I AM L Dec 13 '12 at 7:51

i don't know python much more, but i tried

#!/usr/bin/env python

Each_line = [line.split() for line in open('/tmp/prstat.log')]

for n in xrange(len(Each_line)):
    if '2008' in Each_line[n]:
         print " ".join(Each_line[n])," ".join(Each_line[n+1])
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