Package Manager for deno 🦕

Trex 🦕

Package management for deno (pronounced "tee rex")

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Use Trex


Trex is a package management tool for deno similar to npm but keeping close to the deno philosophy. Packages are cached and only one import_map.json file is generated.

// import_map.json

  "imports":  {
    "http/":  "https://deno.land/std/http/"

For more information about the import maps in deno see import maps.

Additional topics


deno install -A --unstable --import-map=https://deno.land/x/trex/import_map.json -n trex --no-check https://deno.land/x/trex/cli.ts

note: Works with deno >= 1.10.2

we shorten the install command so it's not that long

The permissions that Trex uses are:

  • --allow-net
  • --allow-read
  • --allow-write
  • --allow-run
  • --allow-env

You can give those permissions explicitly.

Updating Trex

Install new version with the -f flag:

deno install -f -A --unstable --import-map=https://deno.land/x/trex/import_map.json -n trex --no-check https://deno.land/x/trex/cli.ts

Or use the upgrade command:

trex upgrade

note: available for versions 0.2.0 or higher. note: if you want to try the latest features before release you can use -the --canary flag.

Verify the installation of Trex:

trex --version

and the console should print the Trex version.

For help on the commands that Trex provides, use:

trex --help


Installing from deno.land

Install the fs, http and fmt modules from std:

trex install --map fs http fmt

note: you can use trex i --map fs http fmt

--map installs packages from the standard library and those hosted at deno.land/x

Installing from nest.land

Install a package hosted on nest.land:

trex install --nest opine@0.13.0

note: if you want to install a package using nest.land you must specify a version explicitly as above

You can install packages from std hosted in nest.land by specifying the package and the version:

trex install --nest fs@0.61.0

Installing from a repository

trex install --pkg [user]/[repo or repo@tag/branch]/[path/to/file] [packageName]


trex install --pkg oakserver/oak@main/mod.ts oak

note: In the event that the repository uses a branch other than master as the main branch, this must be specified

The above downloads oak directly from its repository.

Example import map

All installation methods produce an import_map.json file:

  "imports": {
    "fs/": "https://deno.land/std/fs/",
    "http/": "https://deno.land/std/http/",
    "fmt/": "https://deno.land/std/fmt/"

Downloading packages

Download all the packages listed in the import_map.json similar to npm install:

trex install

Adding custom packages

Install a package from a custom URL source:

trex --custom React=https://dev.jspm.io/react/index.js


  "imports": {
    "http/": "https://deno.land/std/http/",
    "fmt/": "https://deno.land/std/fmt/",
    "oak": "https://deno.land/x/oak/mod.ts",
    "React": "https://dev.jspm.io/react/index.js"

Deleting packages

trex delete React

Remove a specific version from the cache and the import_map.json file:

trex delete fs@0.52.0


  "imports": {
    "fs/": "https://deno.land/std/fs/",
    "http/": "https://deno.land/std/http/",
    "fmt/": "https://deno.land/std/fmt/",
    "oak": "https://deno.land/x/oak/mod.ts"

Removing from cache only works with standard packages and those installed from deno.land/x

Selecting a specific version of a package

Specify a package's version:

trex install --map fs@0.54.0


  "imports": {
    "fs/": "https://deno.land/std@0.54.0/fs/"

note: can be used with third party packages.

Check if a dependencie is outdate

if you want to check if one or more dependencies are out of date, only run trex check command.

trex check

this checks the dependencies and if there are updates for that dependency.

for now only works for deno.land/std and deno.land/x but eventually should work with many registers an cdn

Run Scripts

now you can create command aliases similar to npm run, you just have to create a run.json file with the following structure:

  "scripts": {
    "welcome": "deno run https://deno.land/std@0.71.0/examples/welcome.ts"

note: to run command aliases you must use the command trex run <aliases>

now you can call a command within another or call a deno script like denopack or eggs within a command alias

  "scripts": {
    "start": "trex run welcome",
    "welcome": "deno run https://deno.land/std@0.71.0/examples/welcome.ts",
    "dev": "denon run ./app.ts",
    "build": "aleph build"

Installation life cycle

when the command trex install or trex i executed, you can perform actions before and after the execution of trex install.

execution order:

  • preinstall
  • install
  • postinstall
  "scripts": {
    "start": "trex run welcome",
    "welcome": "deno run https://deno.land/std@0.71.0/examples/welcome.ts",
    "dev": "denon run ./app.ts",
    "build": "aleph build",
    "preinstall": "deno --version",
    "postinstall": "deno test --unstable"

note: you can use the --watch flag to monitor the changes and rerun the script, example: deno run --watch --unstable https://deno.land/std@0.71.0/examples/welcome.ts

you can pass arguments in the command alias and these will be resisted by the file to execute

trex run start --port=3000 --env
console.log(Deno.args); // ["--port=3000", "--env"]

Reboot script alias protocol (rsap)

with trex you can create script aliases that are reloaded every time a file is changed, this can be done using deno's --watch flag. If you would like to have this same functionality but with any command alias you want, you can use trex reboot script protocol which reruns the command alias every time changes are detected in the files and folders you specify


  "scripts": {
    "start": "trex run welcome",
    "welcome": "deno run https://deno.land/std@0.71.0/examples/welcome.ts",
    "dev": "denon run ./app.ts",
    "build": "aleph build"
  "files": ["./app.ts"]

You only have to add the files option in the run.json file and it will only observe the files and folders that you specify, if you leave the array empty it will observe all the files.

for the script alias to use rsap you just need to add the --watch or -w flag to the end of the command alias.


  "scripts": {
    "dev": "go build"
  "files": ["./main.go"]
trex run dev --watch ...args

and of course it can be used with any cli tool, compiler or interpreter.

note: you can create the run file in yaml format

- scripts:
    dev: go build

- files:
    - ./main.go

a limitation of watch mode is that they do not restart the processes that never end as http servers, in those cases we recommend other alternatives such as denon

Virtual cli tool execution

trex exec allows you to run many cli tools hosted at deno.land/x

trex exec aleph init hello_world

trex will fetch aleph's cli and run without installing it locally using deno install, you can also specify the version you want to use.

trex exec aleph@v0.2.28 init hello_world

You can also specify the permissions that the cli will use

trex exec --perms env,read,write,net denon run ./app.ts

you just have to pass the --perms flag followed by the permissions separated by commas


  • env: --allow-env
  • write: --allow-write
  • read: --allow-read
  • net: --allow-net
  • run: --allow-run
  • reload: --reload
  • plugin: --allow-plugin
  • hrtime: --allow-hrtime
  • A: --allow-all

note: if you don't specify the permissions, they are all automatically granted to you

you can also use this combined with the command alias


// run.json
  "scripts": {
    "denon": "trex exec denon run"
  "files": ["./app.ts"]
trex run denon ./app.ts

and yes you can do this:

trex exec trex exec trex exec ....

even this:

trex exec land trex exec land trex exec ....

this functionality is heavily inspired by npx and land. if you need another alternative to trex exec to use in deno, land this is a great option.

Local configuration and global configuration (experimental)

When you work with import maps trex by default will handle everything using an import_map.json file, but what if I want to use an import-map.json or an importMap.json instead?

That's what the global settings are for, basically it allows you to change the behavior of trex with respect to the file where the dependencies will be handled.


trex global-config --importMap=import-map.json

this will change the default name from import_map.json to import-map.json. to obtain the name or format used you must execute the following command.

trex global-config --getImportMap

But what happens if I am working with several people on the same project and we have different configurations? for these cases there is the local configuration or local configuration file. trex.config.json


  "importMap": "importMap.json"

this will tell trex that the format for the import map will be the one dictated by the config file. this allows that there are no problems with the different local configurations of each developer since the configuration file only affects the scope of the project.

note: the file trex.config.json must be at the same level(scope) as the import map for trex to detect it.

the hierarchy that trex respects with the configurations is the following:

graph TD
trex.config.json --> LocalGlobalConfig
LocalGlobalConfig --> defaultTrexConfig

Purge a package or URL

if you want delete a package or url package from cache memory in deno, you can use the purge command to remove from cache memory.


trex purge oak

this finds the oak package in the import_map.json file and removes it from the cache.

trex purge https://deno.land/x/oak@v6.3.1/mod.ts

also can be used with urls

Checking a package's dependency tree

trex tree fs

This prints out something like:

local: C:\Users\trex\AppData\Local\deno\deps\https\deno.land\434fe4a7be02d1875....
type: TypeScript
compiled: C:\Users\trex\AppData\Local\deno\gen\https\deno.land\std\fs\mod.ts.js
map: C:\Users\trex\AppData\Local\deno\gen\https\deno.land\std\fs\mod.ts.js.map
  ├─┬ https://deno.land/std/fs/empty_dir.ts
  │ └─┬ https://deno.land/std/path/mod.ts
  │   ├── https://deno.land/std/path/_constants.ts
  │   ├─┬ https://deno.land/std/path/win32.ts
  │   │ ├── https://deno.land/std/path/_constants.ts
  │   │ ├─┬ https://deno.land/std/path/_util.ts
  │   │ │ └── https://deno.land/std/path/_constants.ts
  │   │ └── https://deno.land/std/_util/assert.ts
  │   ├─┬ https://deno.land/std/path/posix.ts
  │   │ ├── https://deno.land/std/path/_constants.ts
  │   │ └── https://deno.land/std/path/_util.ts
  │   ├─┬ https://deno.land/std/path/common.ts
  │   │ └─┬ https://deno.land/std/path/separator.ts
  │   │   └── https://deno.land/std/path/_constants.ts
  │   ├── https://deno.land/std/path/separator.ts
  │   ├── https://deno.land/std/path/_interface.ts
  │   └─┬ https://deno.land/std/path/glob.ts
  │     ├── https://deno.land/std/path/separator.ts
  │     ├─┬ https://deno.land/std/path/_globrex.ts
  │     │ └── https://deno.land/std/path/_constants.ts
  │     ├── https://deno.land/std/path/mod.ts
  │     └── https://deno.land/std/_util/assert.ts
  ├─┬ https://deno.land/std/fs/ensure_dir.ts
  │ └─┬ https://deno.land/std/fs/_util.ts
  │   └── https://deno.land/std/path/mod.ts
  ├─┬ https://deno.land/std/fs/ensure_file.ts
  │ ├── https://deno.land/std/path/mod.ts
  │ ├── https://deno.land/std/fs/ensure_dir.ts
  │ └── https://deno.land/std/fs/_util.ts
  ├─┬ https://deno.land/std/fs/ensure_link.ts
  │ ├── https://deno.land/std/path/mod.ts
  │ ├── https://deno.land/std/fs/ensure_dir.ts
  │ ├── https://deno.land/std/fs/exists.ts
  │ └── https://deno.land/std/fs/_util.ts
  ├─┬ https://deno.land/std/fs/ensure_symlink.ts
  │ ├── https://deno.land/std/path/mod.ts
  │ ├── https://deno.land/std/fs/ensure_dir.ts
  │ ├── https://deno.land/std/fs/exists.ts
  │ └── https://deno.land/std/fs/_util.ts
  ├── https://deno.land/std/fs/exists.ts
  ├─┬ https://deno.land/std/fs/expand_glob.ts
  │ ├── https://deno.land/std/path/mod.ts
  │ ├─┬ https://deno.land/std/fs/walk.ts
  │ │ ├── https://deno.land/std/_util/assert.ts
  │ │ └── https://deno.land/std/path/mod.ts
  │ └── https://deno.land/std/_util/assert.ts
  ├─┬ https://deno.land/std/fs/move.ts
  │ ├── https://deno.land/std/fs/exists.ts
  │ └── https://deno.land/std/fs/_util.ts
  ├─┬ https://deno.land/std/fs/copy.ts
  │ ├── https://deno.land/std/path/mod.ts
  │ ├── https://deno.land/std/fs/ensure_dir.ts
  │ ├── https://deno.land/std/fs/_util.ts
  │ └── https://deno.land/std/_util/assert.ts
  ├── https://deno.land/std/fs/read_file_str.ts
  ├── https://deno.land/std/fs/write_file_str.ts
  ├── https://deno.land/std/fs/read_json.ts
  ├── https://deno.land/std/fs/write_json.ts
  ├── https://deno.land/std/fs/walk.ts
  └── https://deno.land/std/fs/eol.ts

Integrity checking & lock files

Let's say your module depends on a remote module. When you compile your module for the first time, it is retrieved, compiled and cached. It will remain this way until you run your module on a new machine (e.g. in production) or reload the cache.

But what happens if the content in the remote url is changed? This could lead to your production module running with different dependency code than your local module. Deno's solution to avoid this is to use integrity checking and lock files.

Create a lockfile:

deno cache --lock=lock.json --lock-write file.ts

The above generates a lock.json file.

If you use import_map.json in input file, you can specify it:

deno cache --lock=lock.json --lock-write --import-map=import_map.json --unstable file.ts

See deno document for more info.

Complete example

A simple std server

Install http and fmt:

trex install --map http fmt

Create a simple server:

// server.ts
import { serve } from "http/server.ts";
import { green } from "fmt/colors.ts";

const server = serve({ port: 8000 });

for await (const req of server) {
  req.respond({ body: "Hello World\n" });

Run the server:

deno run --allow-net --import-map=import_map.json --unstable server.ts

note: it is important to use --import-map=import_map.json --unstable

Adding third party packages

Example using oak

Add the master version of oak:

trex i --map oak

This adds oak to the import_map.json file:

  "imports": {
    "http/": "https://deno.land/std/http/",
    "fmt/": "https://deno.land/std/fmt/",
    "oak": "https://deno.land/x/oak/mod.ts"

Then create an oak application. Note the import statement.

// app.ts
import { Application } from "oak";

const app = new Application();

app.use((ctx) => {
  ctx.response.body = "Hello World!";

await app.listen({ port: 8000 });

Run the server:

deno run --allow-net --import-map=import_map.json --unstable app.ts


Contributions are welcome, see CONTRIBUTING GUIDELINES.


Trex is licensed under the MIT license.

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