---
title: Environment Variables
description:
  Learn more about all the environment variables Melos supports and also
  pre-populates.
---

# Environment Variables

These variables are available as environment variables in the commands run by
`melos exec` and in [`exec`](/configuration/scripts#exec) scripts:

```yaml
melos:
  scripts:
    echo:vars:
      exec: echo $MELOS_PACKAGE_NAME $MELOS_PACKAGE_VERSION $MELOS_PACKAGE_PATH
```

The variables that describe a package only exist while `melos exec` runs a
command in that package. When you call `melos exec` yourself, from a terminal or
from a [`run`](/configuration/scripts#run) script, a POSIX shell expands
`$MELOS_PACKAGE_NAME` to an empty string before Melos starts. Wrap the command
in single quotes, or escape the reference as `\$MELOS_PACKAGE_NAME`, so that the
shell started by `melos exec` expands it instead:

```bash
melos exec -- 'echo $MELOS_PACKAGE_NAME'
```

A command substitution in an `exec` script still runs once, before `melos exec`
starts, so the package variables are not defined inside of it. Escape the
substitution to run it in every package instead:

```yaml
melos:
  scripts:
    echo:directory:
      exec: echo \$(basename $MELOS_PACKAGE_PATH)
```

`$MELOS_PACKAGE_NAME` is also replaced in the paths passed to the
`--file-exists` package filter:

```bash
melos exec --file-exists='test_driver/$MELOS_PACKAGE_NAME_e2e.dart' -- echo hello
```

## Defined by Melos

### `MELOS_ROOT_PATH`

The path to the mono-repo root

### `MELOS_PACKAGE_NAME`

The name of the package that's currently executing a script (when using
`melos exec`)

### `MELOS_PACKAGE_VERSION`

The version of the package that's currently executing a script (when using
`melos exec`)

### `MELOS_PACKAGE_PATH`

The path of the package that's currently executing a script (when using
`melos exec`).

### `MELOS_PARENT_PACKAGE_NAME`

The name of the parent package of the example that's currently being executed
in a script (when using `melos exec`).

### `MELOS_PARENT_PACKAGE_VERSION`

The version of the parent package of the example that's currently being executed
in a script (when using `melos exec`).

### `MELOS_PARENT_PACKAGE_PATH`

The path of the parent package of the example that's currently being executed
in a script (when using `melos exec`).

### `MELOS_PUBLISH_DRY_RUN`

Whether the current publish is a dry run or not. This is `true` when running
`melos publish --dry-run` and `false` otherwise.

#### What is a 'parent package'

If an example package exists in a directory that is a child of another package,
then its parent is the 'parent package'. For example; the package
`firebase_auth` has an `example` directory that is also a package, when running
a `melos exec` script in the `example` package then the parent package would be
`firebase_auth`.

Note, this 'parent package' functionality only currently works when the 'child
package' name ends with `example`.

## User Defined

### `MELOS_PACKAGES`

Define a comma delimited list of package names that Melos should focus on. This
will act as the `scope` global package filter, and it will override the `scope`
for all the filtering options defined in the `packageFilters` section.

Melos also sets this variable itself when running a script that declares
[`packageFilters`](/configuration/scripts#packagefilters), so that a `melos`
command invoked by the script is scoped to the selected packages.

### `MELOS_SDK_PATH`

The path to the Dart/Flutter SDK to use. This environment variable has
precedence over the `sdkPath` option in the root `pubspec.yaml`, but is
overridden by the command line option `--sdk-path`.

### `MELOS_QUIET`

Set to `true` to only print warnings, errors and the output of failed commands.
This environment variable has precedence over the
[`quiet`](/configuration/overview#quiet) option in the root `pubspec.yaml`, but
is overridden by the command line options `--quiet` and `--no-quiet`.

Melos also sets this variable itself for the scripts that it runs in quiet mode,
so that a `melos` command invoked by a script is quiet too.

### `MELOS_RUN_UNCHANGED`

Set to `true` to make [`melos exec`](/commands/exec#--sources) run the command
in every package, even in the packages in which the sources did not change. This
has the same effect as the command line option `--run-unchanged`.

Melos also sets this variable itself for the scripts that it runs with
[`melos run --run-unchanged`](/commands/run#--run-unchanged), so that it
applies to every `melos exec` command invoked by a script.

### `MELOS_IGNORE_SOURCES`

Set to `true` to make [`melos exec`](/commands/exec#--ignore-sources) ignore the
sources of commands, so that they run in every package without calculating or
storing checksums, for example on a continuous integration server. This
environment variable has precedence over the
[`ignoreSources`](/configuration/overview#ignoresources) option in the root
`pubspec.yaml`, but is overridden by the command line options
`--ignore-sources` and `--no-ignore-sources`.

Melos also sets this variable itself for the scripts that it runs with
[`melos run --ignore-sources`](/commands/run#--ignore-sources).

### `MELOS_ANSI_STYLES`

Set to `true` to make Melos style its output with colors, even if it does not
write to a terminal, for example on a continuous integration server. Set to
`false` to never style the output.

Melos also sets this variable itself for the scripts that it runs. Melos
captures the output of those scripts, so a `melos` command invoked by a script
cannot detect the terminal on its own and would otherwise lose its colors.

Other tools that are invoked by a script do not write to a terminal either, so
most of them turn off their colors. They usually have an option to turn colors
back on, for example `flutter --color test` or `dart test --color`. Scripts that
need a real terminal can use
[`stdio: inherit`](/configuration/scripts#stdio).