How I use the Zig build system to install ncdu

I have an old Linux system that I intend to backup and then update. Before performing a manual backup I like to understand disk usage. I have used a few different tools for this task:

This year ncdu is 18 years old. A few years ago I read about a rewrite. I was a fan of the original version. Version 2 of ncdu is implemented in Zig. The only Zig software that I regularly use today is Ghostty; and I use Ghostty on both Mac and Linux.

I'm interested in Zig the language and Zig the build system. For example I found the case study of Uber using the Zig tool chain for cross compilation interesting. The Zig website states:

Not only can you write Zig code instead of C or C++ code, but you can use Zig as a replacement for autotools, cmake, make, scons, ninja, etc.

Much more than the alternatives mentioned, I'm interested in learning more about the Zig build system and this post is a chance to try it out. Below I use a Fedora Linux 42 container to build the latest release of ncdu from source. I chose Fedora Linux 42, released on 15 April 2025, because it is the first version to package the Zig ncdu implementation, so system-level dependencies should be straight forward.

Launch a container and install system-level dependencies

Command to launch a container:

incus launch images:fedora/42/cloud c1

Command to install the required system-level dependencies:

incus exec c1 -- dnf install \
  libzstd-devel \
  ncurses-devel \
  minisign \
  git-core \
  wcurl \
  make \
  gcc

Download the latest ncdu and Zig releases

Command to download Zig 0.15.1 and a signature:

incus exec c1 -- wcurl \
  https://ziglang.org/download/0.15.1/zig-x86_64-linux-0.15.1.tar.xz \
  https://ziglang.org/download/0.15.1/zig-x86_64-linux-0.15.1.tar.xz.minisig

Command to verify the download with minisign against the public key from the Zig download page:

incus exec c1 -- minisign \
    -V \
    -m zig-x86_64-linux-0.15.1.tar.xz \
    -P RWSGOq2NVecA2UPNdBUZykf1CCb147pkmdtYxgb3Ti+JO/wCYvhbAb/U

Expected output:

Signature and comment signature verified
Trusted comment: timestamp:1755707121   file:zig-x86_64-linux-0.15.1.tar.xz     hashed

Command to extract the Zig compiler:

incus exec c1 -- tar xf zig-x86_64-linux-0.15.1.tar.xz

Command to clone the source code for the latest release of ncdu:

incus exec c1 -- git clone --config advice.detachedHead=false \
  https://code.blicky.net/yorhel/ncdu.git --branch v2.9.1

It is safe to ignore the warning below, this is displayed because v2.9.1 is an annotated git tag:

warning: refs/tags/v2.9.1 79a0f4f623adfef4488593c3bbfda21e74f34f5c is not a commit!

Build and install

Command to run the build:

incus exec c1 -- sh -c 'PATH="/root/zig-x86_64-linux-0.15.1/:$PATH" make -C ncdu'

Command to install the resulting binary on the host system:

incus file pull c1/root/ncdu/zig-out/bin/ncdu ~/.local/bin

Clean up

Command to stop and delete the container:

incus stop c1 && incus delete c1

Why install GCC above?

I install GCC to avoid an issue relating to the linker script installed as /usr/lib64/libncursesw.so. Although the issue is closed; I cannot confirm it is resolved because I ran into other issues building ncdu with a Zig nightly version. Unfortunately system-level dependencies weren't as straightforward as I expected.

make: Entering directory '/root/ncdu'
zig build --release=fast -Dstrip
install
└─ install ncdu
   └─ compile exe ncdu ReleaseFast native 1 errors
error: ld.lld: unable to find library -ltinfo
error: the following command failed with 1 compilation errors:
/root/zig-x86_64-linux-0.15.1/zig build-exe -D_DEFAULT_SOURCE -D_XOPEN_SOURCE=600 -lncursesw -ltinfo -lzstd -fstrip -OReleaseFast -Mroot=/root/ncdu/src/main.zig -lc --cache-dir .zig-cache --global-cache-dir /root/.cache/zig --name ncdu --zig-lib-dir /root/zig-x86_64-linux-0.15.1/lib/ --listen=-

Build Summary: 0/3 steps succeeded; 1 failed
install transitive failure
└─ install ncdu transitive failure
   └─ compile exe ncdu ReleaseFast native 1 errors

error: the following build command failed with exit code 1:
.zig-cache/o/7ade27cbf6b5118e3c7fe0ce076f4a3f/build /root/zig-x86_64-linux-0.15.1/zig /root/zig-x86_64-linux-0.15.1/lib /root/ncdu .zig-cache /root/.cache/zig --seed 0x1af56ad3 -Z2b12229399a4fdd0 --release=fast -Dstrip
make: *** [Makefile:20: release] Error 1
make: Leaving directory '/root/ncdu

INPUT(libncursesw.so.6 -ltinfo)

Commentary

At first I ignored the Makefile; but I ran into an error: failed to parse shared library: UnexpectedEndOfFile because I was trying to produce a debug build. Now, I am happy with the approach above.

Installing minisign is perhaps extra complexity. The project does not plan to provide "SHA" hashes; though these are published in https://ziglang.org/download/index.json. The instructions above to verify a download are taken from a closed issue.

It was unfortunate to run into the issue around -ltinfo. I am slightly more positive after this experience with the build system. Zig is an attractive systems programming language and tool chain.