Previous: Invoking guix repl, Up: 编程接口 [Contents][Index]
The guix repl command gives you access to a warm and friendly
read-eval-print loop (REPL) (see Invoking guix repl). If you’re
getting into Guix programming—defining your own packages, writing
manifests, defining services for Guix System or Guix Home, etc.—you will
surely find it convenient to toy with ideas at the REPL.
If you use Emacs, the most convenient way to do that is with Geiser
(see 完美的配置), but you do not have to use Emacs to enjoy the
REPL. When using guix repl or guile in the terminal,
we recommend using Readline for completion and Colorized to get colorful
output. To do that, you can run:
guix install guile guile-readline guile-colorized
... and then create a .guile file in your home directory containing this:
(use-modules (ice-9 readline) (ice-9 colorized)) (activate-readline) (activate-colorized)
The REPL lets you evaluate Scheme code; you type a Scheme expression at the prompt, and the REPL prints what it evaluates to:
$ guix repl scheme@(guix-user)> (+ 2 3) $1 = 5 scheme@(guix-user)> (string-append "a" "b") $2 = "ab"
It becomes interesting when you start fiddling with Guix at the REPL. The
first thing you’ll want to do is to “import” the (guix) module,
which gives access to the main part of the programming interface, and
perhaps a bunch of useful Guix modules. You could type (use-modules
(guix)), which is valid Scheme code to import a module (see Using Guile
Modules in GNU Guile Reference Manual), but the REPL provides the
use command as a shorthand notation (see REPL Commands in GNU Guile Reference Manual):
scheme@(guix-user)> ,use (guix) scheme@(guix-user)> ,use (gnu packages base)
Notice that REPL commands are introduced by a leading comma. A REPL command
like use is not valid Scheme code; it’s interpreted specially by the
REPL.
Guix extends the Guile REPL with additional commands for convenience. Among
those, the build command comes in handy: it ensures that the given
file-like object is built, building it if needed, and returns its output
file name(s). In the example below, we build the coreutils and
grep packages, as well as a “computed file” (see computed-file), and we use the scandir procedure to list the
files in Grep’s /bin directory:
scheme@(guix-user)> ,build coreutils
$1 = "/gnu/store/…-coreutils-8.32-debug"
$2 = "/gnu/store/…-coreutils-8.32"
scheme@(guix-user)> ,build grep
$3 = "/gnu/store/…-grep-3.6"
scheme@(guix-user)> ,build (computed-file "x" #~(mkdir #$output))
building /gnu/store/…-x.drv...
$4 = "/gnu/store/…-x"
scheme@(guix-user)> ,use(ice-9 ftw)
scheme@(guix-user)> (scandir (string-append $3 "/bin"))
$5 = ("." ".." "egrep" "fgrep" "grep")
As a packager, you may be willing to inspect the build phases or flags of a given package; this is particularly useful when relying a lot on inheritance to define package variants (see Defining Package Variants) or when package arguments are a result of some computation, both of which can make it harder to foresee what ends up in the package arguments. Additional commands let you inspect those package arguments:
scheme@(guix-user)> ,phases grep
$1 = (modify-phases %standard-phases
(add-after 'install 'fix-egrep-and-fgrep
(lambda* (#:key outputs #:allow-other-keys)
(let* ((out (assoc-ref outputs "out"))
(bin (string-append out "/bin")))
(substitute* (list (string-append bin "/egrep")
(string-append bin "/fgrep"))
(("^exec grep")
(string-append "exec " bin "/grep")))))))
scheme@(guix-user)> ,configure-flags findutils
$2 = (list "--localstatedir=/var")
scheme@(guix-user)> ,make-flags binutils
$3 = '("MAKEINFO=true")
At a lower-level, a useful command is lower: it takes a file-like
object and “lowers” it into a derivation (see Derivations) or a store
file:
scheme@(guix-user)> ,lower grep $6 = #<derivation /gnu/store/…-grep-3.6.drv => /gnu/store/…-grep-3.6 7f0e639115f0> scheme@(guix-user)> ,lower (plain-file "x" "Hello!") $7 = "/gnu/store/…-x"
The full list of REPL commands can be seen by typing ,help guix and
is given below for reference.
Lower object and build it if it’s not already built, returning its output file name(s).
Lower object into a derivation or store file name and return it.
Change build verbosity to level.
This is similar to the --verbosity command-line option (see 普通的构建选项): level 0 means total silence, level 1 shows build events only, and higher levels print build logs.
These REPL commands return the value of one element of the arguments
field of package (see package Reference): the first one show the
staged code associated with #:phases (see Build Phases), the
second shows the code for #:configure-flags, and ,make-flags
returns the code for #:make-flags.
Run exp, a monadic expression, through the store monad. See 仓库monad, for more information.
Enter a new REPL to evaluate monadic expressions (see 仓库monad).
You can quit this “inner” REPL by typing ,q.
Previous: Invoking guix repl, Up: 编程接口 [Contents][Index]