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199 lines
10 KiB
Markdown
199 lines
10 KiB
Markdown
Serval DNA
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==========
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[Serval Project][], September 2016
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[Serval DNA][] is the core component of the [Serval Mesh][] app for Android and
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the [Serval Mesh Extender][] long-range mesh networking device. It is a daemon
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process that performs all the central services of the Serval mesh network
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such as dynamic routing, encryption and authentication, file distribution,
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messaging, and voice telephony.
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Any device with Wi-Fi connectivity that runs the Serval DNA daemon can
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participate in the [Serval mesh network][].
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Download, build and test
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------------------------
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* [INSTALL.md](./INSTALL.md) contains instructions for downloading, building
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and testing Serval DNA on Linux, Mac OS-X, and similar platforms
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* [Notes for Developers](./doc/Development.md) contains useful information for
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developers of Serval DNA, which may also help resolve build issues
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Configuration
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-------------
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* [doc/Servald-Configuration.md](./doc/Servald-Configuration.md) describes how
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to set up and run a Serval DNA daemon
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Documentation
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-------------
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* [INSTALL.md](./INSTALL.md) -- instructions to compile and install Serval DNA
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* [doc/](./doc/) -- technical documentation
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* once Serval DNA is built, its "help" command will print a summary of all the
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operations that servald offers:
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$ ./servald help
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* the following pages in the [Serval Project Wiki][]:
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* [Serval DNA overview][Serval DNA]
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* [Serval DNA development][]
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* [CONTRIBUTORS.md](./CONTRIBUTORS.md) -- individuals who have contributed to
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the software
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Bugs and issues
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---------------
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Bugs can be reported and inspected using the [GitHub issue tracker][Serval DNA issues].
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What is in this repository?
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---------------------------
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This repository contains the [GNU C][] source code for the **servald**
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executable, a [test framework](./testframework.sh) and [test scripts](./tests/)
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written in [Bash][], some [technical documentation](./doc/), and various
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support files for installation and configuration on various platforms.
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The **servald** executable is a multi-purpose program that can be invoked
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directly from the command line, run as a daemon process, or invoked via [JNI][]
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from within a Java program. The **servald** executable is really many commands
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built into one; the command-line arguments select which *command* to run. Some
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commands are stand-alone utilities, some start and stop the servald daemon
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process, some communicate with the servald daemon as an MDP client, and others
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via a two-way [pipe][] called the *monitor interface*.
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The following protocols and services are implemented in **servald**:
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* The **[Distributed Numbering Architecture (DNA)][DNA]** is the key
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innovation that makes mesh telephony viable in the absence of any
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infrastructure, eg, in the aftermath of a natural disaster or in remote
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locations. DNA is a protocol carried over MDP (see below) that asks many
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devices at once if they will answer a phone number (DID). A device will
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respond with its own subscriber identity (SID) if its user has “claimed”
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that DID. This allows phone calls to be established over the mesh using
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conventional phone numbers.
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* The **[Serval Keyring][]** is a flat file containing all the user identities
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on a single device. Each identity is a set of elliptic curve secret
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cryptographic keys that belong to a single “mesh subscriber”, indexed by the
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subscriber's 256-bit public key, called a SID. Each identity in the keyring
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is locked by its own user-chosen password (called a PIN in the code and
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documentation), using elliptic curve cryptography to protect locked entries
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from theft or tampering, and steganography to allow the user to plausibly
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deny the existence of locked identities.
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* The **[Mesh Datagram Protocol (MDP)][MDP]** is Serval's own layer 3 protocol
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designed for secure mesh networking. It is completely independent of
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Internet protocols such as IP and UDP, although for the time being it is
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implemented as an “overlay” network based on UDP/IP because that is the
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interface that Linux and other operating systems provide for sending data
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over Wi-Fi. However, MDP could easily be implemented directly over a layer
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2 data link such as Wi-Fi or Ethernet MAC. MDP uses subscribers' public
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keys (SID) as source and destination addresses, has a 32-bit port number
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analogous to the 16-bit port number used in TCP/IP, and encrypts all packet
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contents by default, using the public key (SID) of the destination.
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* The **[Voice over Mesh Protocol (VoMP)][VoMP]** is Serval's own call
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negotiation and two-way audio streaming protocol used to implement mesh
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voice calls. It fills the same role as SIP/RTS, the dominant protocol used
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for Voice over Internet Protocol, but VoMP is designed for the variable and
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unstable conditions of wireless mesh networks. VoMP's session state model
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and signalling can handle packet loss, mid-call re-routing and re-connection
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where SIP would fail. VoMP's audio streaming can encapsulate many codecs
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and even DTMF (dialpad button) signalling.
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* **[Rhizome][]** is a content storage and distribution service implemented
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using SQLite and a content-exchange protocol based on MDP. It can be used
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to disseminate content like images, videos, documents, software upgrades,
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etc. Each piece of content in Rhizome is called a “bundle”, which has two
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parts: a *manifest* that describes the content, and the *payload*, which is
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the content itself. Each bundle has its own unique cryptographic identifier
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that allows any recipient to verify that it has not been tampered with. A
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bundle's payload may be encrypted by the author so that only the designated
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recipient can read it.
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* The **[MeshMS][]** messaging service sends short text messages using Rhizome
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as its transport. Each message thread is stored and carried in a pair of
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journal bundles, one for each direction (ply).
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* **[Serval Infrastructure][]** services may optionally be deployed on any devices
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in the mesh to expose external services to mesh subscribers and vice versa
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(eg, VoIP gateways, SMS satellite links, packetised web), and to overcome
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scalability limitations of a perfectly decentralised mesh (eg, central
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telephone directory). Serval Infrastructure is implemented as a daemon with
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its own executable called `directory_service`.
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Copyright and licensing
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-----------------------
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Serval DNA is [free software][] produced by the [Serval Project][] and many
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[contributors][]. Its source code is licensed to the public under the [GNU
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General Public License version 2][GPL2]. Its technical documentation is
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licensed to the public under the [Creative Commons Attribution 4.0
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International licence][CC BY 4.0]. All source code and technical documentation
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is freely available from the Serval Project's [serval-dna][] Git repository on
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[GitHub][].
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The copyright in most of the source code in Serval DNA is held by [Serval
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Project Inc.][SPI], a not-for-profit association incorporated in the state of
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South Australia in the Commonwealth of Australia for the purpose of developing
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the Serval mesh software. The [COPYRIGHT][] file contains a full list of all
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those who hold copyright in portions of the Serval DNA source code.
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The [Serval Project][] will accept contributions for which copyright has been
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assigned to [Serval Project Inc.][SPI], or which are licensed to either [Serval
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Project Inc.][SPI] or to the public on terms that allow the Serval Project to
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freely redistribute and re-license the code under non-restrictive terms, for
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example, to release Serval DNA as part of a product distributed through the
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[Apple app store][].
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Individual developers may assign copyright in their contributions by signing
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the [Serval Project Developer Agreement - Individual][individ], and
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organisations by signing the [Serval Project Developer Agreement -
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Entity][entity].
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-----
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**Copyright 2015 Serval Project Inc.**
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**Copyright 2016 Flinders University**
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This document is available under the [Creative Commons Attribution 4.0 International licence][CC BY 4.0].
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[Serval Project]: http://www.servalproject.org/
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[Serval Project Wiki]: http://developer.servalproject.org/
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[Serval DNA]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:servaldna:
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[Serval DNA development]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:servaldna:development
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[Serval Mesh]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:servalmesh:
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[Serval Mesh Extender]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:meshextender:
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[Serval mesh network]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:mesh_network
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[SPI]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:spi
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[serval-dna]: https://github.com/servalproject/serval-dna
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[batphone]: https://github.com/servalproject/batphone
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[Serval DNA issues]: https://github.com/servalproject/serval-dna/issues
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[issue #28]: https://github.com/servalproject/serval-dna/issues/28
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[GNU C]: http://gcc.gnu.org/
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[daemon]: http://en.wikipedia.org/wiki/Daemon_(computing)
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[free software]: http://www.gnu.org/philosophy/free-sw.html
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[contributors]: /servalproject/serval-dna/blob/development/CONTRIBUTORS.md
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[GitHub]: https://github.com/servalproject
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[COPYRIGHT]: ./COPYRIGHT.txt
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[GPL2]: ./GPL-2.0.txt
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[Apple app store]: http://www.fsf.org/blogs/licensing/more-about-the-app-store-gpl-enforcement
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[individ]: http://developer.servalproject.org/files/serval_project_inc-individual.pdf
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[entity]: http://developer.servalproject.org/files/serval_project_inc-entity.pdf
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[DNA]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:dna
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[Serval Keyring]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:keyring
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[MDP]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:mdp
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[VoMP]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:vomp
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[Rhizome]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:rhizome
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[MeshMS]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:meshms
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[Serval Infrastructure]: http://developer.servalproject.org/dokuwiki/doku.php?id=content:tech:serval_infrastructure
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[JNI]: http://en.wikipedia.org/wiki/Java_Native_Interface
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[Bash]: http://en.wikipedia.org/wiki/Bash_(Unix_shell)
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[pipe]: http://www.kernel.org/doc/man-pages/online/pages/man2/pipe.2.html
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[CC BY 4.0]: ./LICENSE-DOCUMENTATION.md
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