Find newest file in directory and then search it

Posted on 2004-04-15
Last Modified: 2007-12-19
I have a batch job that i run about 3 to 4 times a day. It creates a log of format 1262002-1000 am.log i want to find the newest log file and then grep its results. I have the grep part written but am struggling with how to do the opendir and use a array to find the newest file and then run my grep against that.
Question by:gdmacmillan
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Expert Comment

ID: 10836320
why use perl?

if you already have your grep:

grep "searchstring" `ls -tr | tail -1`

tho, if you wanted, you could put that backtick command into perl, too...

Author Comment

ID: 10836341
Sorry forgot to mention im doing this on a windows system thats why im using perl.
LVL 20

Accepted Solution

jmcg earned 440 total points
ID: 10836357
We have been asked something very much like this before:

For your case, I think it might work if you started out with something like the following:

use strict;
use File::stat;

my $newest = [ undef, 0 ];

for ( <*.log> ) {
    my $st = stat($_) or next; # should warn here?
    my $mtime = $st->mtime;

    $newest = [ $_, $mtime] if $mtime > newest->[1] ;

print "most recent file is: ", $newest->[0], "\n";

This should be reasonably efficient and I think I've avoided the typos that plagued that other question. With $newest->[0] in hand as your filename, you can then apply whatever grep code you had already worked out.

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Expert Comment

ID: 10836386

and your log name leaves a little to be desired... is your example from jan 26th? or from dec 6th?

you could scan the filenames into an array and use sort, but only after you did some magic on the names. specifically, you need to alter all the filenames so they can be compared... like using YYYYMMDDHHMM.log instead of what you got with the am's and all...

Expert Comment

ID: 10836389
or, use File::stat as jmcg suggests :P

Author Comment

ID: 10836669
Hi Jcmp,
          yep ive been looking at those other awnsers but i am quite a newbie to perl. The last programming i did was pascal back in college in 90.  I understand we are creating a array which is undefined and then searching through the files to find the newest.  The stat function is used to get info from the flie. What i get stuck at is how do i tell it which directory to go search.

Assisted Solution

fim32 earned 60 total points
ID: 10837127
that's in the for part:

for ( <.*log> ) {

the <.*log> part says search the local directory for all files names .*log, it's a shortcut to using the opendir and such.

Author Comment

ID: 10837161
Doh. So if i run it from that directory it will search that directory? What if i wanted to use it to go search another one?

Expert Comment

ID: 10837330
you could as easily wrap that for loop in a opendir/closedir:

opendir D,"/newdir";
for (readdir D) {
  other stuffs here
closedir D;

or, if you wanted to make sure it was only *log files you were getting, change the abovre for (readdir) to:
for (grep { /.*log/ } readdir D) {

Author Comment

ID: 10843632
Hi fim32 & Jmcg thanks for all your help on this. I have the program working now.

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