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4.1 Defining Packages

The high-level interface to package definitions is implemented in the (guix packages) and (guix build-system) modules. As an example, the package definition, or recipe, for the GNU Hello package looks like this:

(define-module (gnu packages hello)
  #:use-module (guix packages)
  #:use-module (guix download)
  #:use-module (guix build-system gnu)
  #:use-module (guix licenses))

(define hello
    (name "hello")
    (version "2.8")
    (source (origin
             (method url-fetch)
             (uri (string-append "mirror://gnu/hello/hello-" version
              (base32 "0wqd8sjmxfskrflaxywc7gqw7sfawrfvdxd9skxawzfgyy0pzdz6"))))
    (build-system gnu-build-system)
    (arguments `(#:configure-flags '("--enable-silent-rules")))
    (inputs `(("gawk" ,gawk)))
    (synopsis "Hello, GNU world: An example GNU package")
    (description "Guess what GNU Hello prints!")
    (home-page "")
    (license gpl3+)))

Without being a Scheme expert, the reader may have guessed the meaning of the various fields here. This expression binds variable hello to a <package> object, which is essentially a record (see Scheme records in GNU Guile Reference Manual). This package object can be inspected using procedures found in the (guix packages) module; for instance, (package-name hello) returns—surprise!—"hello".

In the example above, hello is defined into a module of its own, (gnu packages hello). Technically, this is not strictly necessary, but it is convenient to do so: all the packages defined in modules under (gnu packages …) are automatically known to the command-line tools (see Package Modules).

There are a few points worth noting in the above package definition:

Once a package definition is in place3, the package may actually be built using the guix build command-line tool (see Invoking guix build). See Packaging Guidelines, for more information on how to test package definitions.

Eventually, updating the package definition to a new upstream version can be partly automated by the guix refresh command (see Invoking guix refresh).

Behind the scenes, a derivation corresponding to the <package> object is first computed by the package-derivation procedure. That derivation is stored in a .drv file under /gnu/store. The build actions it prescribes may then be realized by using the build-derivations procedure (see The Store).

Scheme Procedure: package-derivation store package [system]

Return the <derivation> object of package for system (see Derivations).

package must be a valid <package> object, and system must be a string denoting the target system type—e.g., "x86_64-linux" for an x86_64 Linux-based GNU system. store must be a connection to the daemon, which operates on the store (see The Store).

Similarly, it is possible to compute a derivation that cross-builds a package for some other system:

Scheme Procedure: package-cross-derivation store package target [system]

Return the <derivation> object of package cross-built from system to target.

target must be a valid GNU triplet denoting the target hardware and operating system, such as "mips64el-linux-gnu" (see GNU configuration triplets in GNU Configure and Build System).



Simple package definitions like the one above may be automatically converted from the Nixpkgs distribution using the guix import command.

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