Building a readline application is cool, but readline gives you the
basics and you must still build a REPL around it: loop and read
commands, catch a
C-d, ask confirmation to quit, print the
general help, the help of a command, setup the completion of commands, the
completion of their arguments, load an init file,
replic does this for you.
You can use
replic as a ready-to-use executable or as a library.
Using the executable, you can define functions and variables in
~/.replic.lisp, give them completion candidates, and use them
straight away on the replic command line.
With the library you can automatically build a REPL and turn functions you already have into commands in the readline prompt, with the process described below.
There are a few examples below, in
src/examples.lisp and expect more to come.
This is an attempt at generalizing what I did several times with
What this is not:
- this is not a Lisp REPL. See cl-repl for that (itself not a replacement for Slime ;) )
- this is not a shell. See shcl.
Example applications built on replic:
You can download the executable (a 14MB zipped download, a 60Mo
GNU/Linux x64 self-contained binary, instant start-up !), make it
chmod +x replic) and run it:
or build it yourself.
- the library is on Quicklisp (since the 2019-01-07 dist) and on Ultralisp:
or clone this repo into
then build the executable with
__Note__: you need the cl-readline library from Quicklisp of end of
may, 2018 (for the read and write history feature). See
for a quick clone.
and see the available commands:
replic > help replic > help help
Now add commands in your lisp init file (see next section) or build an application with it (see the Developer section).
User: the executable and the init file
Given the example
~/.replic.lisp below, you can
hello <name> (completion for
where <name> can be completed from what was given to
(in-package :replic.user) (defparameter *names* '() "List of names (string) given to `hello`. Will be autocompleted by `goodbye`.") (defun hello (name) "Takes only one argument. Adds the given name to the global `*names*` variable, used to complete arguments of `goodbye`. " (format t "hello ~a~&" name) (push name *names*)) (defun goodbye (name) "Says goodbye to name, where `name` should be completed from what was given to `hello`." (format t "goodbye ~a~&" name)) (replic.completion:add-completion "goodbye" (lambda () *names*)) (export '(hello goodbye))
Note that only the
export‘ed functions and parameters will be taken
See more examples in the
src/examples.lisp file of this repository.
Define a default completion function for a command’s arguments
First write a function or a variable and
export it. It becomes a command
in the command line interface.
You can tell a command to complete its arguments against a given variable or function:
(replic.completion:add-completion "goodbye" (lambda () *names*)) ;; or (replic.completion:add-completion "goodbye" #'my-function)
Now everytime you type
goodbye fooTAB, the lambda function is run and
you get completion candidates that start with “foo”.
The functions must return a list of strings.
When you have many functions whose arguments should be completed similarly, you can set a default completion function:
(setf replic.completion:*default-command-completion* #'my-function)
A different completion function for each argument
Each parameter of a command can be completed with its own method.
Let’s define a command
say that wants first a greeting message, and
then a name:
(defun say (verb name) (format t "~a, ~a !~&" verb name))
We can provide the completion functions in the same order as the arguments:
(replic.completion:add-completion "say" (list "greetings" "\"nice to see you\"") (lambda () *names*))
Now if you type
say TAB you get the two greeting choices. After you
pick one and press TAB again, you get the names that were given to
You get a built-in
help command that shows the documentation of
functions and variables:
replic > help Available commands ================== help ... Print the help of all available commands. reload ... NIL set ... Change a variable, see its value, or see all variables. quit --- Quit the application. Available variables =================== *verbose* ... If true, print debugging information during the program execution.
Write a preamble and a postamble in
You can read the help of a specific command or variable (with completion):
help shows the first paragraph of the
functions/parameters docstring, the
help <cmd> function is more
complete and shows all of it.
Setting and seeing variables
set can be used with zero, one or two arguments:
shows all available variables,
this prints the value of this variable (use auto-completion),
set *variable* new-value
and this sets a new value. “yes”, “true” and “t” denote true.
We kept the “earmuffs” to denote variables.
Replic reads an
init-like configuration file. It searches a
.replic.conf file under
~/.config/ and at the user’s home
These are the default parameters with their default values:
[default] confirm-exit = true verbose = false prompt = > history = true write-history = true
“true”, “True” and “t” are truthy and “false”, “False” and “nil” are falsy.
By default, replic reads and sets the options of the
You can have a section per program:
[myprogram] option = val
Options of config files are overriden by command line arguments.
Developer: using replic as a library with an existing system
replic is in Quicklisp (2019-01-07):
Follow the documentation below, and see example applications on the wiki.
Change the prompt
You can change the prompt. It defaults to “> “. It can contain ansi colors.
(setf replic:*prompt* (cl-ansi-text:green "replic > "))
You can add a prefix to it, for example one that changes with the state of the application (current directory,…):
(setf replic:*prompt-prefix* (format t "(~a) " "sthg"))
and concatenate the two with
[optional] Load base commands (help, reload, set)
If you want to have the base commands (
quit), import the base package:
Create commands from a package’s exported functions
This is the core of the library.
Create the commands you’ll find at the readline prompt from the exported functions and variables of a given package:
To exclude functions, use the
(replic.completion:functions-to-commands :my-package :exclude '("main"))
For more control, you can create a command from one given function:
(replic.completion:add-command :function :package) ;; add a variable: (replic.completion:add-variable :*variable* :package)
It is generally a good idea to have a package for the lisp functions you’ll use at the repl, and another package for the ones that must be commands at the readline interface.
[optional] Automatically printing the result of functions
A lisp function from a library usually returns some result and doesn’t
necessarily print it. If you want
replic to automatically print it,
ask it like so:
(replic:autoprint-results-from :my-package :exclude '("exclude" "those-functions"))
[optional] Overriding the default printing of results
We export a default
print-result (result) function, which is called
for functions whose results are printed automatically (see
A user can override this function in his/her lisp init file:
;; ~/.replic.lisp (in-package :replic) (defun print-result (result) (format t "=== this new result is:~&") (format t "~a~&" result))
In doing so, you should see a warning at startup:
WARNING: redefining REPLIC:PRINT-RESULT in DEFUN
Load a config file
replic searches by default for a
.replic.conf (see above). The
replic.config:apply-config takes as first parameter a
package name (as a symbol):
**Changed in march, 2020** This will read the
[mypackage] section of
the configuration files.
As an optional second parameter, you can give another file name:
(replic.config:apply-config :mypackage ".mysoftware.conf")
The exported variables from the package can then be
overriden in the config file. For example, the
:replic package exports
(:export :main :confirm :repl :help :set :reload ;; settings :*help-preamble* :*help-postamble* :*prompt* :*prompt-prefix* :*confirm-exit* :*write-history* :*verbose*))
so we can configure:
[default] write-history = true verbose = true prompt = my silly prompt
and so on.
Start the repl
Start the repl:
That’s it. You didn’t have to write the REPL.
Variables that are exported from a package on the lisp side will
be automacitally available for the config file and read when the
application starts up. The rule is that in the config file, we don’t
use earmuffs (
foo). Lispers shall use a lispy config
The available variables are:
*verbose*(bool): if true, print debugging information during the program execution.
*confirm-exit*(bool): if true (the default), ask for confirmation when a user tries to exit the program with a
*prompt*(str): the readline prompt. Defaults to simply
>. Can contain ansi colours (use
*confirm-exit*(t or nil): if
t(the default), ask for confirmation when the user tries to exit the command line with a
*write-history*(t or nil): if
t(the default), write the commands to the app’s history. (this needs
cl-readlinesuperior to may, 2018)
*help-preamble*: text to display at the beginning of the help.
*help-postamble*: text to display last.
- print colored output from markdown or code with pygments:
(format-markdown txt :lang "md"). It outputs text for a console display with ansi colours. Needs pygments, or does nothing.
For example, you can change the completion behavior. This:
inserts the first completion candidate, even if there are many, instead of showing the list of choices under the prompt.
If you prefer vi mode:
set editing-mode vi
etc. See readline’s documentation.
This is a generalization on
cl-readline. See also the simple cl-readline
example. Once you’ve built two even basic readline apps you’ll want
to factorize the common parts.
We want to store a list of commands (functions, “verbs”) and a list of
variables (the ones to use with “set”). We want to read them from any
Lisp file, hence we need to remember the package they come from. This
mechanism is provided through an interface in
Clone this repo in QL’s local projects (
Build the executable:
You can build the binary with SBCL core compression (see commented .asd). We passed from a 78 to a 18MB binay, but the startup time increased from 0.04 to 0.26s, which is noticeable. We don’t use compression by default.
Develop and test interactively into the console
By starting a swank server in the (real) Lisp repl we can compile code in our editor and try instantly in the terminal, without re-building the executable. See this cl-charms crash course for now. Some details need fixing.
Simpler and still handy, you can add
trace statements into your
.replic.lisp, call the
reload command and see the effects. Then,
(untrace) and reload.
- read an option from a given section.
only reads and sets options of the “myprogram” section and set the
matching variables found in
- v0.12, upcoming in Quicklisp of november
- added: a different completion for each command argument
- added: completion for sentences (strings in quotes).
- Quicklisp, october 2019
- fixed 0.11 regression: arguments had to always be surrounded by quotes (sept, 14th). We can now write =command arg1 “second arg”= as expected.
- v0.11 (end of june, 2019)
- added a declarative way to automatically print a function’s result. The default function can be overriden by users (in order to, for example, color the output).
- fixed: a quoted string on the readline prompt is now understood as one single argument.