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https://github.com/stackbuilders/atomic-write

Writes files atomically in Haskell while preserving permissions
https://github.com/stackbuilders/atomic-write

atomic-actions file-management hacktoberfest hacktoberfest-2023 haskell

Last synced: 15 days ago
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Writes files atomically in Haskell while preserving permissions

Host: GitHub
URL: https://github.com/stackbuilders/atomic-write
Owner: stackbuilders
License: mit
Created: 2015-02-06T16:30:11.000Z (almost 10 years ago)
Default Branch: main
Last Pushed: 2024-08-30T15:12:30.000Z (4 months ago)
Last Synced: 2024-12-05T21:51:21.300Z (28 days ago)
Topics: atomic-actions, file-management, hacktoberfest, hacktoberfest-2023, haskell
Language: Haskell
Homepage:
Size: 1.17 MB
Stars: 18
Watchers: 27
Forks: 1
Open Issues: 3
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: docs/CONTRIBUTING.md
- License: LICENSE
- Code of conduct: docs/CODE_OF_CONDUCT.md

Awesome Lists containing this project

README

        [![Build](https://github.com/stackbuilders/atomic-write/actions/workflows/build.yml/badge.svg?branch=master)](https://github.com/stackbuilders/atomic-write/actions/workflows/build.yml)

[![Hackage version](https://img.shields.io/hackage/v/atomic-write.svg)](http://hackage.haskell.org/package/atomic-write)

[![All Contributors](https://img.shields.io/badge/all_contributors-6-orange.svg?style=flat-square)](#contributors-)

# Atomic Write

Atomic Write assists with atomic modification of files using

Haskell. It is a wrapper for using the atomic mv(1) operation which

correctly sets permissions based on the original file, or on system

defaults if no file previously exists.

## How it works

On most Unix systems, mv is an atomic operation. This makes it simple to write to a file atomically just by using the mv operation. However, this will destroy the permissions on the original file. This library does the following to preserve permissions while atomically writing to a file:

If an original file exists, take those permissions and apply them to the temp file before mving the file into place.

If the original file does not exist, create a following with default permissions (based on the currently-active umask).

This way, when the file is mv'ed into place, the permissions will be the ones held by the original file.

This library is based on similar implementations found in common libraries in Ruby and Python:

- [Ruby on Rails includes a similar method called atomic_write](https://apidock.com/rails/File/atomic_write/class)

- [Chef includes atomic update functionality](https://github.com/chef/chef/blob/c4631816132fcfefaba3d123a1d0dfe8bc2866bb/lib/chef/file_content_management/deploy/mv_unix.rb#L23:L71)

- [There is a python library for atomically updating a file](https://github.com/sashka/atomicfile)

## Usage

To use `atomic-write`, import the module corresponding to the type you wish to write atomically, e.g., to write a (strict) ByteString atomically:

```import System.AtomicWrite.Writer.ByteString```

Then you can use the atomicWriteFile function that accepts a FilePath and a ByteString, e.g.:

```atomicWriteFile myFilePath myByteString```

See the

[Haddock documentation](http://hackage.haskell.org/package/atomic-write).

## Contributors ✨

Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

  

    

      
_{Justin S. Leitgeb}
💻

      
_{William R. Arellano}
💻

      
_{Alexander Mejía}
💻

      
_{Agustin Camino}
💻

      
_{Juan Paucar}
💻

      
_{Barbara Morantes}
💡

    

  

  

    

      

        

          Add your contributions

        

      

    

  

This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!

## License

MIT, see [the LICENSE file](LICENSE).

## Contributing

Do you want to contribute to this project? Please take a look at our [contributing guideline](/docs/CONTRIBUTING.md) to know how you can help us build it.

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