Finding the Latest Modified Time In A Mount Point

User wanted to decommission a particular mount point but needed to ensure no files/directories was updated recently. So the question is how can we find out exactly the latest modified time in this mount point.

My initial approach was to do a couple of find /mount/point -mtime -... -ls to roughly locate the last modified time. I used the divide and conquer approach, eg, starts with 100 days, if no file return change to 200 days, else 50 days, ... This approach can only give me a rough estimate. If I can list the timestamp in the ISO 8601 format YYYYMMDDTHHMMSS, I can just simply sort it and the latest modified time will be the last record. I know find is not able to do that, but find2perl can convert a find command to Perl code. With Perl, I can modify it to output to the format that I want.

$ /usr/perl5/5.8.4/bin/find2perl /mount/point -ls
#! /usr/perl5/5.8.4/bin/perl -w
    eval 'exec /usr/perl5/5.8.4/bin/perl -S $0 ${1+"$@"}'
        if 0; #$running_under_some_shell

use strict;
use File::Find ();

# Set the variable $File::Find::dont_use_nlink if you're using AFS,
# since AFS cheats.

# for the convenience of &wanted calls, including -eval statements:
use vars qw/*name *dir *prune/;
*name   = *File::Find::name;
*dir    = *File::Find::dir;
*prune  = *File::Find::prune;

sub wanted;
sub ls ();


my @rwx = qw(--- --x -w- -wx r-- r-x rw- rwx);
my @moname = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);

my (%uid, %user);
while (my ($name, $pw, $uid) = getpwent) {
    $user{$uid} = $name unless exists $user{$uid};
}

my (%gid, %group);
while (my ($name, $pw, $gid) = getgrent) {
    $group{$gid} = $name unless exists $group{$gid};
}


# Traverse desired filesystems
File::Find::find({wanted => \&wanted}, '/mount/point');
exit;


sub wanted {
    my ($dev,$ino,$mode,$nlink,$uid,$gid);

    (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
    ls;
}


sub sizemm {
    my $rdev = shift;
    sprintf("%3d, %3d", ($rdev >> 8) & 0xff, $rdev & 0xff);
}

sub ls () {
    my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
        $atime,$mtime,$ctime,$blksize,$blocks) = lstat(_);
    my $pname = $name;

    $blocks
        or $blocks = int(($size + 1023) / 1024);

    my $perms = $rwx[$mode & 7];
    $mode >>= 3;
    $perms = $rwx[$mode & 7] . $perms;
    $mode >>= 3;
    $perms = $rwx[$mode & 7] . $perms;
    substr($perms, 2, 1) =~ tr/-x/Ss/ if -u _;
    substr($perms, 5, 1) =~ tr/-x/Ss/ if -g _;
    substr($perms, 8, 1) =~ tr/-x/Tt/ if -k _;
    if    (-f _) { $perms = '-' . $perms; }
    elsif (-d _) { $perms = 'd' . $perms; }
    elsif (-l _) { $perms = 'l' . $perms; $pname .= ' ->>' . readlink($_); }
    elsif (-c _) { $perms = 'c' . $perms; $size = sizemm($rdev); }
    elsif (-b _) { $perms = 'b' . $perms; $size = sizemm($rdev); }
    elsif (-p _) { $perms = 'p' . $perms; }
    elsif (-S _) { $perms = 's' . $perms; }
    else         { $perms = '?' . $perms; }

    my $user = $user{$uid} || $uid;
    my $group = $group{$gid} || $gid;

    my ($sec,$min,$hour,$mday,$mon,$timeyear) = localtime($mtime);
    if (-M _ > 365.25 / 2) {
        $timeyear += 1900;
    } else {
        $timeyear = sprintf("%02d:%02d", $hour, $min);
    }

    printf "%5lu %4ld %-10s %3d %-8s %-8s %8s %s %2d %5s %s\n",
            $ino,
                 $blocks,
                      $perms,
                            $nlink,
                                $user,
                                     $group,
                                          $size,
                                              $moname[$mon],
                                                 $mday,
                                                     $timeyear,
                                                         $pname;
    1;
}

Just change the original printf to this one:

printf("%04d%02d%02dT%02d%02d%02d %d %s\n", $timeyear, $mon+1, $mday, $hour, $min, $sec, $mtime, $pname);

There is a lot of stuff not needed from the find2perl output. We can trim it down to just suit our need, which is to locate the latest modified time. My friend found this on the Internet that do exactly this task. It is very efficient because the script will keep track of the latest time stamp.

#!/bin/perl
use File::Find;
@ARGV = ('.') unless @ARGV;
my ($age, $name);
sub youngest {
    return if defined $age && $age > (stat($_))[9];
    $age = (stat(_))[9];
    $name = $File::Find::name;
}
find(\&youngest, @ARGV);
print "$name " . scalar(localtime($age)) . "\n";