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IPC for Real-Time Robot Control
C Common Lisp Python Java C++ Shell Other
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Ach is an Inter-Process Communication (IPC) mechanism and library. It is especially suited for communication in real-time systems that sample data from physical processes. Ach eliminates the Head-of-Line Blocking problem for applications that always require access to the newest message. Ach is efficient, robust, and formally verified. It has been tested and demonstrated on a variety of physical robotic systems. Source code for Ach is available under an Open Source BSD-style license.


./configure && make && make install

See the INSTALL file for details.

Alternatively, if you are using Debian or Ubuntu, you can use the APT repo.

  1. Add the following to /etc/apt/sources:

    deb squeeze

    (substitute the codename for your distribution in place of squeeze, e.g. wheezy, precise)

  2. sudo apt-get update && sudo apt-get install libach-dev ach-utils ach-dkms

  3. sudo dpkg-reconfigure ach-utils


See ./INSTALL for details on generating the documentation.



Language bindings are included for Common Lisp, Python, and Java.

  • Common Lisp bindings use CFFI and can be loaded with ASDF.

  • Python bindings are a C extension module and a Python module 'ach'. This can be installed either via make install or via Python's distutils/pip.

  • C++ bindings wrap the C API. See ./include/Ach.hpp

  • Java bindings via the Java Native Interface (JNI). See ./doc/javadoc or

See the INSTALL file for details.


Ach has been formally verified using the SPIN model checker. This formal model is included in the source distribution under the ./spin/ directory.

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