lock

README

go4

go4.org is a collection of packages for Go programmers.

They started out living in Perkeep's repo and elsewhere but they have nothing to do with Perkeep, so we're moving them here.

Details

• single repo. go4 is a single repo. That means things can be changed and rearranged globally atomically with ease and confidence.

• no backwards compatibility. go4 makes no backwards compatibility promises. If you want to use go4, vendor it. And next time you update your vendor tree, update to the latest API if things in go4 changed. The plan is to eventually provide tools to make this easier.

• forward progress because we have no backwards compatibility, it's always okay to change things to make things better. That also means the bar for contributions is lower. We don't have to get the API 100% correct in the first commit.

• no Go version policy go4 packages are usually built and tested with the latest Go stable version. However, go4 has no overarching version policy; each package can declare its own set of supported Go versions.

• code review contributions must be code-reviewed. We're trying out Gerrithub, to see if we can find a mix of Github Pull Requests and Gerrit that works well for many people. We'll see.

• CLA compliant contributors must agree to the Google CLA (the same as Go itself). This ensures we can move things into Go as necessary in the future. It also makes lawyers at various companies happy. The CLA is not a copyright assignment; you retain the copyright on your work. The CLA just says that your work is open source and you have permission to open source it. See https://golang.org/doc/contribute.html#cla

• docs, tests, portability all code should be documented in the normal Go style, have tests, and be portable to different operating systems and architectures. We'll try to get builders in place to help run the tests on different OS/arches. For now we have Travis at least.

Contact

For any question, or communication when a Github issue is not appropriate, please contact the Perkeep mailing list.

Documentation

Overview

Package lock is a file locking library.

Index

• func Lock(name string) (io.Closer, error)

Functions

func Lock

func Lock(name string) (io.Closer, error)

Lock locks the given file, creating the file if necessary. If the file already exists, it must have zero size or an error is returned. The lock is an exclusive lock (a write lock), but locked files should neither be read from nor written to. Such files should have zero size and only exist to co-ordinate ownership across processes.

A nil Closer is returned if an error occurred. Otherwise, close that Closer to release the lock.

On Linux, FreeBSD and OSX, a lock has the same semantics as fcntl(2)'s advisory locks. In particular, closing any other file descriptor for the same file will release the lock prematurely.

Attempting to lock a file that is already locked by the current process has undefined behavior.

On other operating systems, lock will fallback to using the presence and content of a file named name + '.lock' to implement locking behavior.