README.md

@@ -2,6 +2,16 @@
 
 ## Running the examples
 
+### examples/fib
+
+The fib example performs fibonacci trivially on a fixed number. It is the most basic example of a process that requires no privilege, excluding `Stdout` to print the result.
+
+To run this example:
+
+    cargo build
+    cargo build --example fib
+    target/debug/clone-shim -s examples/fib/spec.json target/debug/examples/fib
+
 ### examples/basic
 
 The basic example instructs the shim to spawn two processes, each of which writes "hello from main{1,2}!" to stdout.

examples/fib/main.rs

@@ -0,0 +1,16 @@
+fn main() {
+    println!("fib(1) = {}", fib(1));
+    println!("fib(7) = {}", fib(7));
+    println!("fib(19) = {}", fib(19));
+}
+
+fn fib(i: u64) -> u64 {
+    let mut a = 0;
+    let mut b = 1;
+
+    for _ in 0..i {
+        (a, b) = (b, a + b);
+    }
+
+    a
+}

examples/fib/spec.json

@@ -0,0 +1,30 @@
+{
+    "entrypoints": {
+        "fib": {
+            "args": [
+                "BinaryName"
+            ],
+            "environment": [
+                "Stdout",
+                {
+                    "Filesystem": {
+                        "host_path": "/lib/x86_64-linux-gnu/libgcc_s.so.1",
+                        "environment_path": "/lib/libgcc_s.so.1"
+                    }
+                },
+                {
+                    "Filesystem": {
+                        "host_path": "/lib/x86_64-linux-gnu/libc.so.6",
+                        "environment_path": "/lib/libc.so.6"
+                    }
+                },
+                {
+                    "Filesystem": {
+                        "host_path": "/lib64/ld-linux-x86-64.so.2",
+                        "environment_path": "/lib64/ld-linux-x86-64.so.2"
+                    }
+                }
+            ]
+        }
+    }
+}

src/main.rs

@@ -98,7 +98,7 @@ fn main() {
         };
 
         match run(&args) {
-            Ok(_) => exitcode::OK,
+            Ok(code) => code,
             Err(e) => {
                 error!("error: {}", e);
                 -1