#concurrent #file #semaphore #lock #mutex


A library for concurrently writing to files in a safe and efficient manner

5 unstable releases

Uses old Rust 2015

0.3.1 Feb 26, 2020
0.3.0 Sep 14, 2019
0.2.0 May 15, 2018
0.1.1 May 12, 2018
0.1.0 May 12, 2018

#127 in Concurrency

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semalock is a Rust library for controlling concurrent access to files on POSIX operating systems in an efficient manner.

It uses a combination of POSIX named semaphores and exclusive file locks to safely and efficiently acquire exclusive access to a file. This has been observed to be particularly efficient on Linux, with under 5% of CPU time spent on lock overhead with 8192 processes.


The following shows usage of semalock. This program opens /some/file and appends some text to it. Try it with GNU parallel to measure performance amongst multiple competing processes.

// Acquire and open a file and semaphore
let mut lock = Semalock::new(Path::new("/some/file"));

// Do some stuff to the file
lock.with(|lock| {
        .and_then(|_| lock.file.write(b"hello world\n"))

Supported Operating Systems

The following operating systems have been tested:

  • GNU/Linux 4.16

The following operating systems have not been tested but should work:

  • FreeBSD
  • GNU/Linux 2.6+
  • macOS 10.4+
  • NetBSD
  • OpenBSD

Supported operating systems must support provide the following:

  • flock
  • sem_get_value
  • sem_open
  • sem_post
  • sem_timedwait
  • sem_unlink

The following will not work:

  • Windows NT

Release Notes

0.3.1 - 2020-02-25

  • Fix a compilation error on x86

0.3.0 - 2019-09-13

  • Semalock::with now takes an FnOnce instead of an Fn.
  • Various project hygiene changes

0.2.0 - 2018-05-14

  • Initial release.

Developer Notes

To run the tests, execute the following:

cargo test

To release the create, perform the following:

  1. Edit Cargo.toml, bumping the version as appropriate.
  2. Edit README.md, adding an entry to the Release Notes.
  3. Commit these changes and push them to master.
  4. Create and push a tag that starts with "v" -- e.g. "v0.4.0"


Jason Longshore hello@jasonlongshore.com