Checking for broken links in directory structures
Dead End
![Photo by Adam Birkett on Unsplash Photo by Adam Birkett on Unsplash](/var/linux_magazin/storage/images/media/linux-magazine-eng-us/images/261_photo-by-adam-birkett-on-unsplash_dead-end/816606-1-eng-US/261_Photo-by-Adam-Birkett-on-Unsplash_Dead-End_medium.png)
Photo by Adam Birkett on Unsplash
Broken links can wreak havoc in directory structures. This article shows you how to use scripts to avoid having your links lead to a dead end.
During a restore process, nothing is more disappointing than discovering that some of the links in your previously backed up data no longer work. Although the link is still there, the target no longer exists, resulting in the link pointing nowhere. These broken data structures can also cause problems when you are developing software and publishing it in the form of an archive, or if you need to install different versions of an application.
Finding and fixing broken links manually takes a lot of effort. You can avoid this scenario by using scripts and Unix/Linux tools to check for broken links in directory structures. In this article, I'll look at several ways to check the consistency of these data structures and detect broken links. Read on to avoid hiccups for you and your users.
Sample Data
As an example, I will use the directory structure shown in Figure 1, which is similar to a piece of software or a project directory that you might encounter in the wild. You can easily create a tree such as Figure 1 with the tree
command [1].
The directory tree in Figure 1 contains two versions of the software. There are three links: One points to the old version (named old
), one to the current version (named current
), and the third to a data file named dataset3
(which is missing).
Options
A small, manageable project structure like Figure 1 can be tested and checked manually. With larger projects, however, this quickly leads to errors because you are bound to overlook something. To automate the testing procedure, I rummaged around in my Unix/Linux toolbox and came up with four options that are suitable for everyday use: a shell script as a combination of a recursive function and a for
loop over all the files and directories, a special call to find
, a Python script, and the tools symlinks
, FSlint, rmlint
, and chase
.
Shell Script
The shell script (Listing 1) uses a recursive function named check()
. check()
only expects one parameter: the directory you want it to check for broken links (line 16). In the function, a for
loop iterates across all entries (lines 2 to 14).
Listing 1
find-broken-links.sh
01 function check { 02 for entry in $1/*; do 03 # echo "check $entry ... " 04 if [ -d "$entry" ]; then 05 check $entry 06 else 07 if [ -L "$entry" ]; then 08 target=$(readlink "$entry") 09 if [ ! -e "$target" ]; then 10 echo "broken link: from $entry to $target" 11 fi 12 fi 13 fi 14 done 15 } 16 check $1
For each entry, check()
first checks whether the entry actually is a directory (line 4). If so, the function is called again with this directory as a parameter (line 5). Otherwise, two more tests are made: Is it a link (line 7), and, if so, where does it point to (lines 8 and 9)? In line 8, the readlink
command returns the target to which the link points and stores the result in the local variable target
.
In line 9, the script checks if the link target exists. If not, the function sends an error message to that effect to stdout
(line 10). The routine ignores entries in the directory that are not links. Once the entire list has been processed, check()
returns to the call point. After processing the entire original directory, the script exits.
If you now call the script, you will see output similar to that in Listing 2. I made the call using a period (.
) for the current directory as the starting point. The output includes two lines because current
points to version2
and my function follows the link.
Listing 2
Output of find-broken-links.sh
$ ./find-broken-links.sh . broken link: from ./project/current/data/dataset3 to project/version1/data/dataset3 broken link: from ./project/version2/data/dataset3 to project/version1/data/dataset3
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
![Learn More](https://www.linux-magazine.com/var/linux_magazin/storage/images/media/linux-magazine-eng-us/images/misc/learn-more/834592-1-eng-US/Learn-More_medium.png)
News
-
Canonical Offers 12-Year LTS for Open Source Docker Images
Canonical is expanding its LTS offering to reach beyond the DEB packages with a new distro-less Docker image.
-
Plasma Desktop 6.1 Released with Several Enhancements
If you're a fan of Plasma Desktop, you should be excited about this new point release.
-
SUSE Offers CentOS 7 Support with Liberty Linux Lite
SUSE's Liberty Linux support offering now includes CentOS 7, which means businesses won't be forced to migrate those servers for some time.
-
Ubuntu's App Center Finally Supports Local Installs Again
If you regularly download .deb files and would prefer a GUI method of installing, Ubuntu has your back.
-
AlmaLinux Now Supports Raspberry Pi 5
If you're looking to create with the Raspberry Pi 5 and want to use AlmaLinux as your OS, you're in luck because it's now possible.
-
Kubuntu Focus Releases New Iterations of Ir14 and Ir16 Laptops
If you're a fan of the Kubuntu Focus laptops or have been waiting for the right time to purchase one, that time might be now.
-
NixOS 24.05 Is Ready for Prime Time
The latest release of NixOS (Uakari) has arrived and offers its usual reproducible, declarative, and reliable goodness.
-
Linux Lite 7.0 Officially Released
Based on Ubuntu 24.04 and kernel 6.8, Linux Lite version 7 now offers more options than ever.
-
KaOS Linux 2024.05 Adds Bcachfs Support and More
With updates all around, KaOS Linux now includes support for the bcachefs file system.
-
TUXEDO Computers Unveils New Iteration of the Stellaris Laptop Line
The Stellaris Slim 15 is the 6th generation and includes either an AMD or Intel CPU