Finding world-writable files in local directories only

Over at Stack Overflow I asked how to scan a local filesystem ignoring all remote mount points. I only really wanted a push in the right direction and received it. After clacking away on my keyboard I think I might have what I what I need. I ask for an evaluation to determine if it fulfills the requirements:

• Scan every local directory for world-writable files ignoring "special" directories (/sys, /proc, /dev)

• Ignore directories

• Ignore files on any remote filesystems which may be mounted

• Ignore any files in an "exclude" list

I'm quite certain it could be drastically optimized and any suggestions are welcome as are any suggestions for a better algorithm. However, rewriting the script is secondary to performing the task properly.

I've tested it and I'm fairly confident that I've created what I want. I just need some extra eyes to confirm.

```
#!/usr/bin/perl

# Directives which establish our execution environment
use warnings;
use strict;
use Fcntl ':mode';
use File::Find;
no warnings 'File::Find';
no warnings 'uninitialized';

# Variables used throughout the script
my $DIR = "/var/log/tivoli/";
my $MTAB = "/etc/mtab";
my $PERMFILE = "world_writable_w_files.txt";
my $TMPFILE = "world_writable_files.tmp";
my $EXCLUDE = "/usr/local/etc/world_writable_excludes.txt";
my $ROOT = "/";
my @devNum;

# Create an array of the file stats for "/"
my @rootStats = stat("${ROOT}");

# Compile a list of mountpoints that need to be scanned
my @mounts;

open MT, ") {
if ($_ =~ /ext[34]/) {
my @line = split;
push(@mounts, $line[1]);

}

}

close MT;

# Read in the list of excluded files and create a regex from them
my $regExcld = do {
open XCLD, ";
chomp @ignore;
local $" = '|';
qr/@ignore/;

};

# Create a regex containing mountpoint dev numbers to compare file device numbers to.
my $devRegex = do {
chomp @devNum;
local $" = '|';
qr/@devNum/;

};

# Create the output file path if it doesn't already exist.
mkdir("${DIR}" or die "Cannot execute mkd

Processing mount points

This can be improved in many ways:

# Compile a list of mountpoints that need to be scanned
my @mounts;
open MT, ") {
  if ($_ =~ /ext[34]/) {
    my @line = split;
    push(@mounts, $line[1]);
  }
}

close MT;

Using bare names for file handles is not recommended:
replace MT with my $MT, and ` with .

The comment talks about local mount points.
That's too vague, when in fact you're looking specifically for ext3 and ext4 filesystems.

You could simplify if ($_ =~ /ext[34]/) as if (/ext[34]/).

You could put the entire while loop inside a map, and it will be still readable.

Putting it together, you can rewrite like this:

open my $MT, "));

close $MT;

Note that if you didn't find any mount points,
the script has nothing to process, so it should exit:

die 'no mount points to process' unless @mounts;

Try to apply these techniques everywhere in the script,
especially the bit about filehandlers.

# Read in the list of excluded files and create a regex from them
my $regExcld = do {
  open XCLD, ";
  chomp @ignore;
  local $" = '|';
  qr/@ignore/;
};

As earlier, replace XCLD with my $XCLD or something.
You also forgot to close it.

Btw, a common way to shorten my @arr = ; chomp @arr as chomp(my @arr = ).

Most importantly,
should it be really a fatal error if the file with excluded patterns doesn't exist?
It might make sense to make this optional.
Perhaps issue a warning instead, something like this:

my $regExcld = do {
  if (open my $fh, ");
      close($fh);
      local $" = '|';
      qr/@ignore/;
  } else {
      warn "Cannot open ${EXCLUDE}, $!\n";
      undef;
  }
};

This bit seems pointless:

# Create a regex containing mountpoint dev numbers to compare file device numbers to.
my $devRegex = do {
  chomp @devNum;
  local $" = '|';
  qr/@devNum/;
};

Because @devNum is an empty array in your script,
you never actually gave it any values.

This is quite strange:

# Create the output file path if it doesn't already exist.
mkdir("${DIR}" or die "Cannot execute mkdir on ${DIR}, $!") unless (-d "${DIR}");

You misplaced the die:
it will run if "${DIR}" is empty,
not if mkdir fails.

Also, there's no need whatsoever to double-quote ${DIR}`.

Corrected and simplified:

mkdir($DIR) or die "Cannot execute mkdir on ${DIR}, $!" unless -d $DIR;

StackExchange Code Review Q#46611, answer score: 4