feat: Add "Hello, world!" C-based example

Signed-off-by: Alexander Jung <[email protected]>

README.md

@@ -23,6 +23,7 @@ kraft pkg ls --apps --update
 
 | | Example |
 |-|:-|
+| ![](https://raw.githubusercontent.com/unikraft/catalog/main/icons/c.svg) | [Simple "Hello, world!" application written in C](https://github.com/unikraft/catalog/tree/main/examples/helloworld-c) |
 | ![](https://raw.githubusercontent.com/unikraft/catalog/main/icons/python3.svg) | [Simple Flask 3.0 HTTP Web Server](https://github.com/unikraft/catalog/tree/main/examples/http-python3.10-flask3.0) |
 | ![](https://raw.githubusercontent.com/unikraft/catalog/main/icons/python3.svg) | [Simple Python 3.10 HTTP Web Server with `http.server.HTTPServer`](https://github.com/unikraft/catalog/tree/main/examples/http-python3.10) |
 

examples/helloworld-c/Kraftfile

@@ -0,0 +1,13 @@
+spec: v0.6
+
+name: helloworld
+
+unikraft: stable
+
+targets:
+- fc/arm64
+- fc/x86_64
+- linuxu/x86_64
+- qemu/arm64
+- qemu/x86_64
+- xen/x86_64

examples/helloworld-c/Makefile.uk

@@ -0,0 +1,3 @@
+$(eval $(call addlib,apphelloworld))
+
+APPHELLOWORLD_SRCS-y += $(APPHELLOWORLD_BASE)/main.c

examples/helloworld-c/README.md

@@ -0,0 +1,27 @@
+# Simple "Hello, world!" C Program on Unikraft
+
+This directory contains an example C-based "Hello, world!" example.
+
+To run this example, [install Unikraft's companion command-line toolchain `kraft`](https://unikraft.org/docs/cli).
+
+Then, clone this repository and cd into this directory.
+You can then build the project with:
+
+```
+kraft build
+```
+
+In the above command, `kraft build` will prompt you with the target you wish to compile for.
+If you are unsure, select `qemu/` and your host's architecture, e.g. `qemu/x86_64`.
+
+Once built, you can execute the unikernel via:
+
+```
+kraft run
+```
+
+## Learn more
+
+- [How to build unikernels](https://unikraft.org/docs/cli/building)
+- [How to run unikernels locally](https://unikraft.org/docs/cli/running)
+- [The `Kraftfile` specification](https://unikraft.org/docs/cli/reference/kraftfile/latest)

examples/helloworld-c/main.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+	printf("Hello, world!\n");
+
+	return 0;
+}