Filesystem

This is a simple filesystem example. This WASI P1 module writes a file to a preopened directory, reads it back, and prints the result to stdout — verifying that the guest has read/write access to the host filesystem. For this example we need to enable preopened directories in the guest's configuration. To do this, we need to set the PROPLET_PREOPENED_DIRS environment variable to /tmp in the guest's configuration.

export PROPLET_PREOPENED_DIRS="/tmp"

Source Code

The source code is available in the examples/filesystem directory.

Loading...

Create Task

To create a task for this example, we need to build the example to wasm and then create a task with the wasm file.

cd propeller
make filesystem

Now we can create a task with the wasm file:

curl -X POST "http://localhost:7070/tasks" \
-H "Content-Type: application/json" \
-d '{"name": "_start"}'

Your output should look like this:

{
  "id": "9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841",
  "name": "_start",
  "kind": "standard",
  "state": 0,
  "cli_args": null,
  "inputs": [10, 20],
  "daemon": false,
  "encrypted": false,
  "start_time": "0001-01-01T00:00:00Z",
  "finish_time": "0001-01-01T00:00:00Z",
  "created_at": "2026-02-13T12:41:28.911748133Z",
  "updated_at": "0001-01-01T00:00:00Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

Upload Wasm

Now we need to upload the wasm file:

curl -X PUT "http://localhost:7070/tasks/9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841/upload" \
-F "file=@$(pwd)/build/filesystem.wasm"

Your output should look like this:

{
  "id": "9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841",
  "name": "_start",
  "kind": "standard",
  "state": 0,
  "file": "...<redacted>...",
  "cli_args": null,
  "daemon": false,
  "encrypted": false,
  "start_time": "0001-01-01T00:00:00Z",
  "finish_time": "0001-01-01T00:00:00Z",
  "created_at": "2026-02-13T13:56:34.479984121Z",
  "updated_at": "2026-02-13T13:56:50.205271293Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

Start Task

Now we can start the task:

curl -X POST "http://localhost:7070/tasks/9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841/start"

Your output should look like this:

{ "started": true }

The results of the task will be something like this.

curl -X GET "http://localhost:7070/tasks/9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841"

Your output should look like this:

{
  "id": "9fa47dfa-d96a-4fb5-a3e5-07aa9abdb841",
  "name": "_start",
  "kind": "standard",
  "state": 3,
  "file": "...<redacted>...",
  "cli_args": null,
  "daemon": false,
  "encrypted": false,
  "proplet_id": "a95517f9-5655-4cf5-a7c8-aa00290b3895",
  "results": "",
  "start_time": "2026-02-13T13:56:55.42199427Z",
  "finish_time": "2026-02-13T13:56:55.574175392Z",
  "created_at": "2026-02-13T13:56:34.479984121Z",
  "updated_at": "2026-02-13T13:56:55.574175341Z",
  "next_run": "0001-01-01T00:00:00Z",
  "priority": 50
}

Invoking Using WasmTime

wasmtime --dir /tmp ./build/filesystem.wasm

The results of the task will be something like this.

Writing 88 bytes to /tmp/proplet-fs-test-1770991174.txt
Write OK
Read back 88 bytes:
Proplet filesystem test
Timestamp: 1770991174
Path: /tmp/proplet-fs-test-1770991174.txt
Round-trip verification OK
Append OK
Listing /tmp:
  .ICE-unix
  .X1-lock
  .X11-unix
  .XIM-unix
  .fbdffd3bf7dbbafd-00000000.so
  .font-unix
  .org.chromium.Chromium.STgQkz
  gopls-tempmod259847075
  juju-wakatime-cli-config-mutex
  node-compile-cache
  org.chromium.Chromium.xjwT6F
  proc-macro-srv12d4b-0
  proc-macro-srv1dace-0
  proc-macro-srv1dacf-0
  proc-macro-srv1f152-0
  proc-macro-srv1f153-0
  proc-macro-srv1f154-0
  proc-macro-srv27fb4-0
  proc-macro-srv27fb5-0
  proc-macro-srv27fb6-0
  proc-macro-srv27fb7-0
  proc-macro-srv2bddc-0
  proc-macro-srv2bddd-0
  proc-macro-srv2bdde-0
  proc-macro-srv2bddf-0
  proc-macro-srv2bde0-0
  proplet-fs-test-1770991174.txt
  proplet_c8b06138-6542-49dc-9633-f382c4a965db.wasm
  scoped_dir71lcW5
  scoped_dir8W0hZm
  sddm-:0-mkdKqV
  sddm-auth-907d5f22-aa44-47f1-a045-c2e8ff71056d
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-bluetooth.service-0O7EFY
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-dbus-broker.service-RkfelQ
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-iio-sensor-proxy.service-vUI7Xx
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-polkit.service-hZZn8R
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-systemd-logind.service-mEtxyF
  systemd-private-2d3804d1b11b4918b1f3c0d3c7c1c5c8-upower.service-51AZUz
Delete OK
All filesystem operations succeeded

Filesystem

Source Code

Create Task

Upload Wasm

Start Task

Invoking Using WasmTime

On this page