Take the 2-minute tour ×
Code Review Stack Exchange is a question and answer site for peer programmer code reviews. It's 100% free, no registration required.

I'm working on a Unix machine where I can't use more than vanilla Perl, and I'm using Perl5.8. This script exits with a 1 if the current directory size is smaller than 1 GB (the character after -d is a literal "tab" character).

my $du = `du --si | tail -1 | cut -d"   " -f1`;
chomp $du;
if (substr($du, -1) ne "G") {
    exit 1;
exit 0;

This is gross, but I know the data is in du --si so I can write it in 30 seconds. Is there a cleaner, more robust way?

share|improve this question
Why tail -1? Doesn't that just choose one of the subdirectories arbitrarily? –  200_success Apr 30 at 23:29
I believe the last line of that output is the size of everything (it's the directory ., which is the current directory). The other lines are sizes of subdirectories. –  corykendall May 1 at 0:30

3 Answers 3

up vote 4 down vote accepted

I agree with @rolfl that this would be much simpler as a one-line shell pipeline. The -s option to du makes it produce a total. awk is a good tool to use for processing multi-column text.

du -s --si | awk '$1 ~ /G/ { exit 1 }'

However, the --si option seems to be a non-portable GNU extension. A more portable version would look at the number of 512-byte blocks. The magic number 1953125 is \$\dfrac{10^9}{512}\$.

du -s | awk '$1 < 1953125 { exit 1 }'

The second version also works even if the total is in the terabyte or exabyte range.

There is an inefficiency, though: you should be able to exit early as soon as you find that the total exceeds 1 GB. For that, you would go back to Perl, but with a proper Perl program instead of a wrapper around du.

use File::Find;
use strict;

my $sum = 0;
my %seen_inodes;
find(sub {
    my ($inode, $blocks) = (stat)[1, 12] or die "${File::Find::name}: $!";

    # Do not double-count hard links
    if (!$seen_inodes{$inode}) {
        $seen_inodes{$inode} = 1;
        $sum += 512 * $blocks;
        exit 0 if $sum >= 1_000_000_000;
}, ".");
exit 1;
share|improve this answer

It is unusual on Code Review, to recommend a different approach, but this process can be simplified a whole bunch..... and avoid perl entirely.....

du -s -B 1 | grep -P -q '^\d{10,}+\s.*'

It breaks down as follows:

du -s -B 1

print a summary (no details for each file), with a byte-per-block size ... i.e. print the number of bytes in the current directory.

Then, using grep (and perl-compatible regex).... use quiet output, which returns 0 on a successful match, and 1 on no-match.

In other words, make sure the line starts with at least 10 digits.... i.e. >= 1,000,000,000 bytes.

Putting it together, the grep will be successful if the current directory is at least 1GB.

I tested this with:

du -s -B 1 | grep -P -q '^\d{10,}+\s.*' && echo "Bigger than 1G" || echo "less than 1G"


This is compatible with your original code, which uses --si on du, which uses 1,000,000,000 bytes to represent GB. If you want to use GiB ( \$2^{31}\$ ) then it is actually substantially harder ....

share|improve this answer

Calling du to calculate the full size is Ok, as it is not a trivial task. Everything else is better done on the Perl side. Simpler and cleaner.

my $du = `du -bs .`;
my $bytes = $du =~ /^(\d+)/ or die "du failed";
if ($bytes > 1e9) {
    print "directory is bigger than 1GB\n"
share|improve this answer
Hi, and welcome to code review. du -s . does not count the number of bytes used ... but the number of kiloBytes. Consider adding the -B 1 option to du –  rolfl Jun 13 at 11:19
@rolfl, corrected, thank you. –  salva Jun 13 at 12:37

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.