# Stack root The Stack root is a directory where Stack stores important files. On Unix-like operating systems and Windows, Stack can be configured to follow the XDG Base Directory Specification if the environment variable `STACK_XDG` is set to any non-empty value. However, Stack will ignore that configuration if the Stack root location has been set on the command line or the `STACK_ROOT` environment variable exists. ## Location The location of the Stack root depends on the operating system, whether Stack is configured to use the XDG Base Directory Specification, and/or whether an alternative location to Stack's default 'programs' directory has been specified. The location of the Stack root can be configured by setting the [`STACK_ROOT`](../configure/environment_variables.md#stack_root) environment variable or using Stack's [`--stack-root`](../configure/global_flags.md#-stack-root-option) option on the command line. === "Unix-like" The Stack root contains snapshot packages; (by default) tools such as GHC, in a `programs` directory; Stack's global [configuration](../configure/yaml/index.md) file (`config.yaml`); and Stack's [`global-projects`](../configure/yaml/index.md) directory. The default Stack root is `~/.stack`. === "Windows" The default Stack root is `$Env:APPDATA\stack`. If the `LOCALAPPDATA` environment variable exists, then the default location of tools is `$Env:LOCALAPPDATA\Programs\stack`. Otherwise, it is the `programs` directory in the Stack root. !!! warning If there is a space character in the `$Env:LOCALAPPDATA` path (which may be the case if the relevant user account name and its corresponding user profile path have a space) this may cause problems with building packages that make use of the GNU project's `autoconf` package and `configure` shell script files. That may be the case particularly if there is no corresponding short name ('8 dot 3' name) for the directory in the path with the space (which may be the case if '8 dot 3' names have been stripped or their creation not enabled by default). If there are problems building, it will be necessary to override the default location of Stack's 'programs' directory to specify an alternative path that does not contain space characters. Examples of packages on Hackage that make use of `configure` are `network` and `process`. On Windows, the length of filepaths may be limited (to [MAX_PATH](https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=cmd)), and things can break when this limit is exceeded. Setting a Stack root with a short path to its location (for example, `C:\sr`) can help. === "Windows (Command Prompt)" The default Stack root is `%APPDATA%\stack`. If the `LOCALAPPDATA` environment variable exists, then the default location of tools is `%LOCALAPPDATA%\Programs\stack`. Otherwise, it is the `programs` directory in the Stack root. !!! warning If there is a space character in the `%LOCALAPPDATA%` path (which may be the case if the relevant user account name and its corresponding user profile path have a space) this may cause problems with building packages that make use of the GNU project's `autoconf` package and `configure` shell script files. That may be the case particularly if there is no corresponding short name ('8 dot 3' name) for the directory in the path with the space (which may be the case if '8 dot 3' names have been stripped or their creation not enabled by default). If there are problems building, it will be necessary to override the default location of Stack's 'programs' directory to specify an alternative path that does not contain space characters. Examples of packages on Hackage that make use of `configure` are `network` and `process`. On Windows, the length of filepaths may be limited (to [MAX_PATH](https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=cmd)), and things can break when this limit is exceeded. Setting a Stack root with a short path to its location (for example, `C:\sr`) can help. === "XDG Base Directory Specification" The Stack root is `/stack`. If the `XDG_DATA_HOME` environment variable does not exist, the default is `~/.local/share/stack` on Unix-like operating systems and `%APPDATA%\stack` on Windows. The location of `config.yaml` is `/stack`. If the `XDG_CONFIG_HOME` environment variable does not exist, the default is `~/.config/stack` on Unix-like operating systems and `%APPDATA%\stack` on Windows. This approach treats: * the project-level configuration file that is common to all projects without another such file in their project directory or its ancestor directories as _data_ rather than as part of Stack's own _configuration_; * the snapshots database as essential data rather than as non-essential data that would be part of a _cache_, notwithstanding that Stack will rebuild that database as its contents are needed; and * the Pantry store as essential data rather than as non-essential data that would be part of a _cache_, notwithstanding that Stack will download the package index and rebuild the store if it is absent. An alternative to the default location of tools such as GHC can be specified with the [`local-programs-path`](../configure/yaml/non-project.md#local-programs-path) configuration option. The location of the Stack root is reported by command: ~~~text stack path --stack-root ~~~ The full path of Stack's global configuration file is reported by command: ~~~text stack path --global-config ~~~ The location of tools such as GHC for the current platform is reported by command: ~~~text stack path --programs ~~~ ## Contents The contents of the Stack root depend on the operating system, whether Stack is configured to use the XDG Base Directory Specification, and/or whether an alternative location to Stack's default 'programs' directory has been specified. === "Unix-like" The Stack root contains snapshot packages; (by default) tools such as GHC, in a `programs` directory; Stack's global [configuration](../configure/yaml/index.md) file (`config.yaml`); and Stack's [`global-projects`](../configure/yaml/index.md) directory. === "Windows" The Stack root contains snapshot packages; Stack's global [configuration](../configure/yaml/index.md) file (`config.yaml`); and Stack's [`global-projects`](../configure/yaml/index.md) directory. The default location of tools such as GHC and MSYS2 is outside of the Stack root. === "XDG Base Directory Specification" If Stack is following the XDG Base Directory Specification, the Stack root contains what it would otherwise contain for the operating system, but Stack's global configuration file (`config.yaml`) may be located elsewhere. ### `config.yaml` This is Stack's global configuration file. For further information, see the documentation for non-project specific [configuration](../configure/yaml/non-project.md#non-project-specific-configuration). If the file is deleted, and Stack needs to consult it, then Stack will create a file with default contents. ### `stack.sqlite3` This is a 'user' database that Stack uses to cache certain information. The associated lock file is `stack.sqlite3.pantry-write-lock`. ### `.stack-work` directory (optional) Stack can build when there is no project-level configuration file (including one in the `global-project` directory of the Stack root); for example, as a result of a [`stack script`](../commands/script_command.md) command (at the command line or in a [Stack interpreter options comment](scripts.md) in a Haskell script file). When it does so, the directory corresponding to a project directory is the Stack root. Stack will create its work directory, named `.stack-work` by default, in the Stack root. If the work directory is deleted, and Stack needs that work directory, then Stack will recreate it. ### `global-project` directory This contains: * an explanation of the directory (`README.txt`); * the project-level configuration file (`stack.yaml`) for the global project and its associated lock file (`stack.yaml.lock`); and * if created, Stack's working directory (`.stack-work`) for the global project. If the project-level configuration file is deleted, and Stack needs to consult it, then Stack will recreate the contents of the directory. ### `pantry\hackage` directory This contains a local cache of the package index. If the contents of the directory are deleted, and Stack needs to consult the package index, then Stack will seek to download the latest package index. !!! info Stack depends on package `pantry` which, in turn, depends on package `hackage-security`. The latter handles the local cache of the package index. The type `CacheLayout` represents the location of the files that are cached. `pantry` uses `cabalCacheLayout :: CacheLayout`, the layout that Cabal (the tool) uses. That is what specifies the names of the files used to cache the package index, including `00-index.tar` and `00-index.tar.gz`. ### `pantry` directory This contains: * the Pantry database used by Stack (`pantry.sqlite3`) and its associated lock file (`pantry.sqlite2.pantry-write-lock`). If the database is deleted, and Stack needs to consult it, then Stack will seek to create and initialise it. The database is initialised with information from the package index; and * a database of package versions that come with each version of GHC (`global-hints-cache.yaml`). ### `programs` directory This contains a directory for the platform. That directory contains for each installed Stack-supplied tool: * the archive file for the tool. This can be deleted; * a file indicating the tool is installed (`.installed`); and * a directory for the tool. To remove a Stack-supplied tool, delete all of the above. If Stack needs a Stack-supplied tool and it is unavailable, then Stack will seek to obtain it. ### `scripts` directory (optional) If the `--compile` or `--optimize` and `--use-root` flags are used with the [`stack script`](../commands/script_command.md) command, then this contains: * script-specific locations, each containing all the compilation outputs (inclduing the executable) generated by the command. If the `scripts` directory, or a script-specific location within it, is deleted, and Stack needs that directory, then Stack will recreate it. ### `setup-exe-cache` directory This contains a directory for the platform. That directory contains, for each version of GHC (an associated version of Cabal (the library)) that Stack has used, an executable that Stack uses to access Cabal (the library). If the contents of the directory are deleted, and Stack needs the executable, then Stack will seek to rebuild it. ### `setup-exe-src` directory See the documentation for the [`setup-exe-cache` directory](#setup-exe-cache-directory). This contains the two source files (`setup-.hs` and `setup-shim-.hs`) that Stack uses to build the executable. If the contents of the directory are deleted, and Stack needs the executable, then Stack will recreate them. The hash in the names of the source files is a hash of arguments passed to GHC when building the executable and the contents of the two source files. The content of the `setup-.hs` file is the familiar: ~~~haskell import Distribution.Simple main = defaultMain ~~~ The content of the `setup-shim-.hs` file uses `main` except when the executable is called with arguments `repl` and `stack-initial-build-steps`. Then Stack uses Cabal (the library) to create the autogenerated files for every configured component. Stack's `stack ghci` or `stack repl` commands call the executable with those arguments. ### `snapshots` directory This contains a directory for each snapshot that Stack creates when building immutable dependencies of projects. If the contents of the directory are deleted, and the snapshot is not available to Stack when it builds, then Stack will recreate the snapshot. ### `templates` directory This contains a `.hsfile` for each project template that Stack has used. For further information, see the [`stack templates`](../commands/templates_command.md) command documentation. If the contents of the directory are deleted, an Stack needs a project template, then Stack will seek to download the template. ### `upload` directory This may contain saved credentials for uploading packages to Hackage (`credentials.json`).