diff --git a/examples/interactive/cli-platform/src/lib.rs b/examples/interactive/cli-platform/src/lib.rs
index 96d010fa3f..683c1112f1 100644
--- a/examples/interactive/cli-platform/src/lib.rs
+++ b/examples/interactive/cli-platform/src/lib.rs
@@ -391,3 +391,25 @@ pub extern "C" fn roc_fx_envVarUtf8(key: &RocStr) -> RocStr {
 
     RocStr::from(val.as_str())
 }
+
+#[no_mangle]
+pub extern "C" fn roc_fx_writeUtf8(path: &RocStr, string: &RocStr) {
+    write_bytes(path, string.as_str().as_bytes())
+}
+
+#[no_mangle]
+pub extern "C" fn roc_fx_writeBytes(path: &RocStr, bytes: &RocList<u8>) {
+    write_bytes(path, bytes.as_slice())
+}
+
+fn write_bytes(path: &RocStr, bytes: &[u8]) {
+    // TODO return Result
+    let mut file = File::create(path.as_str()).unwrap();
+    file.write_all(bytes).unwrap();
+}
+
+#[no_mangle]
+pub extern "C" fn roc_fx_errLine(line: &RocStr) {
+    let string = line.as_str();
+    eprintln!("{}", string);
+}