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 (package (name "hello") (version "2.8") (source (origin (method url-fetch) (uri (string-append "mirror://gnu/hello/hello-" version ".tar.gz")) (sha256 (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 "http://www.gnu.org/software/hello/") (license gpl3+)))
Without being a Scheme expert, the reader may have guessed the meaning
of the various fields here. This expression binds variable
<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,
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
(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:
sourcefield of the package is an
<origin>object. Here, the
(guix download)is used, meaning that the source is a file to be downloaded over FTP or HTTP.
mirror://gnu prefix instructs
url-fetch to use one of
the GNU mirrors defined in
sha256 field specifies the expected SHA256 hash of the file
being downloaded. It is mandatory, and allows Guix to check the
integrity of the file. The
(base32 …) form introduces the
base32 representation of the hash. You can obtain this information with
guix download (see Invoking guix download) and
hash (see Invoking guix hash).
When needed, the
origin form can also have a
listing patches to be applied, and a
snippet field giving a
Scheme expression to modify the source code.
build-systemfield specifies the procedure to build the package (see Build Systems). Here, gnu-build-system represents the familiar GNU Build System, where packages may be configured, built, and installed with the usual
./configure && make && make check && make installcommand sequence.
argumentsfield specifies options for the build system (see Build Systems). Here it is interpreted by gnu-build-system as a request run configure with the
inputsfield specifies inputs to the build process—i.e., build-time or run-time dependencies of the package. Here, we define an input called
"gawk"whose value is that of the gawk variable; gawk is itself bound to a
Note that GCC, Coreutils, Bash, and other essential tools do not need to be specified as inputs here. Instead, gnu-build-system takes care of ensuring that they are present (see Build Systems).
However, any other dependencies need to be specified in the
inputs field. Any dependency not specified here will simply be
unavailable to the build process, possibly leading to a build failure.
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
object is first computed by the
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).
<derivation> object of package for system
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:
<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
(see GNU configuration triplets in GNU
Configure and Build System).
definitions like the one above may be automatically converted from the
Nixpkgs distribution using the
guix import command.