ghc-atomic-write

Atomically write to a file on POSIX-compliant systems while preserving permissions. 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 `mv`ing 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: * <http://apidock.com/rails/File/atomic_write/class Ruby on Rails includes a similar method called atomic_write> * <https://github.com/chef/chef/blob/c4631816132fcfefaba3d123a1d0dfe8bc2866bb/lib/chef/file_content_management/deploy/mv_unix.rb#L23:L71 Chef includes atomic update functionality> * <https://github.com/sashka/atomicfile There is a python library for atomically updating a file> 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.

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