Lisp Executable
The lisp-executable library provides a language for defining and creating programs that can be used from the Unix shell instead of the Lisp read-eval-print-loop (REPL).
Table of Contents
1 Introduction
The goal of this Common Lisp library is to provide a convenient abstraction to creating executable programs that can interact easily with other tools that accompany the Unix shell. The abstraction should be familiar and straight forward to use.
The library consists of
- a language for defining programs that accept command line arguments.
- the ability to automatically generate an executable for a defined program.
- an ASDF:COMPONENT so that executables can be built using an ASDF:OPERATION.
The library provides two different styles of passing command line arguments to the defined program
- Program
- A program which accepts options and arguments with options appearing anywhere on the command line.
- Dispatcher
- A program which dispatches to other programs. Example
software of this style would be
xargs
,git
andsvn
.
Lastly, the automatic executable creation relies heavily on ASDF. It is assumed that all programs are declared within an ASDF system.
Automatic executable creation has been implemented for SBCL, ECL, CLISP, CCL and CMUCL.
2 Getting Started Quickly
- Create an ASDF system to manage your program.
;; File lisp-executable-example.asd (eval-when (:compile-toplevel :load-toplevel :execute) (asdf:load-system "lisp-executable")) (defsystem lisp-executable-example :components ((:modules "example/" :serial t :components ((:file "main") (lisp-executable:executable "example-program" :program ("LISP-EXECUTABLE.EXAMPLE" "EXAMPLE-PROGRAM"))))))
- Create
main.lisp
and specify your program.;; File example/main.lisp (defpackage "LISP-EXECUTABLE.EXAMPLE" (:use "COMMON-LISP" "LISP-EXECUTABLE")) (in-package "LISP-EXECUTABLE.EXAMPLE") (define-program example-program (&options help) (cond (help (format t "Help has arrived.")) (t (format t "You are doomed."))) (terpri))
- Create the executable.
(asdf:oos 'lisp-executable:create-executables-op "lisp-executable-example")
- Invoke from the command line.
$ example/example-program You are doomed. $ example/example-program --help Help has arrived. $
3 Design
The API is separated in to two parts (i) the definition of the command line arguments the program accepts (ii) the implementation on how to associate command line arguments to the program argument symbols.
The following terms are used in this document to describe the various components of programs that accept command line arguments:
- Command line program
- The program that is being invoked from the command line.
- Command line arguments
- The list of arguments being passed to the program.
- Program option (or option)
- A command line argument that modifies how the command line program performs its task. Program options can accept parameters.
4 Defining a Program
The first type of command line program introduced is one where the
program options can appear at any position within the command line
arguments. For example, the following two invocations of the command
line program process-file
are equivalent
$ process-file input output -v $ process-file -v input output
To define this type of program you use the macro
LISP-EXECUTABLE:DEFINE-PROGRAM
.
(defmacro define-program (program-name program-lambda-args &body body))
The symbol PROGRAM-NAME
is used to identify the command line
program. The format of PROGRAM-LAMBDA-ARGS
is presented in the next
section. Finally, the code that uses the command line arguments is
placed in BODY
.
4.1 Program Lambda Args
The type of command line arguments accepted by the program is
encapsulated within the PROGRAM-LAMBDA-ARGS
form. The different
types are
- Option
- Option arguments change the behaviour of the command line program.
- Argument
- An argument which is not an option.
- Others
- A collection of non option arguments.
4.1.1 Options
Within the option argument type there are three subtypes depending on whether the declared option accepts a parameter:
- No parameter option
- On or off switch. e.g.
--verbose
- Non mandatory parameter option
- The option can appear with or without an
argument. e.g.
--debug
and--debug=high
- Mandatory parameter option
- The option must appear with an
argument. e.g.
--exclusion-list=file.txt
It should be noted that the manner in which options and their
parameters are read from the command line is determined by the
*COMMAND-LINE-ARGUMENTS-READER*
object.
An example of declaring the different types of options is as follows
(define-program program (&options help (debug-level debug-level-value 1) (file file-value)))
Notice that all option command line arguments declared in a
PROGRAM-LAMBDA-ARGS
must be proceeded with the symbol
&OPTIONS
. The PROGRAM
example can accept three options HELP
,
DEBUG-LEVEL
and FILE
. The value of these symbols throughout the
body of PROGRAM
can be either non NIL
or NIL
depending on
whether the option was found on the command line.
The symbol HELP
is a no parameter option. The option DEBUG-LEVEL
is a non mandatory parameter option. If a parameter to DEBUG-LEVEL
is found on the command line, the value of this parameter is assigned
to the symbol DEBUG-LEVEL-VALUE
. If no parameter is found, then
DEBUG-LEVEL-VALUE
is bound to 1
. The option FILE
is a mandatory
parameter option with its parameter value assigned to the symbol
FILE-VALUE
.
- Converting to other types
For options that are parameterized, the parameter value read from the command line will be of typeSTRING
by default. Automatic conversion to other types can be specified using theCONVERSION-FUNCTION
declaration expression.(define-program program (&options (file file-value) (debug-level debug-level-value 1) help) (declare (conversion-function (integer 0 3) debug-level)))
User supplied conversion functions can be used by simply using the symbol that names the function. For more information please see the section on conversion functions.
- Option Identifiers
In the above example, the symbolFILE
will be set using the string--file
on the command line if it is present. Sometimes it is convenient to specify other strings which are equivalent identifiers for the same option. To accommodate this behaviour the declarationIDENTIFIERS
is provided.(define-program program (&options (file file-value) (debug-level debug-level-value 1) help) (declare (identifiers file "file" #\f) (identifiers help "help" #\h)))
Valid identifiers are strings and characters.
Again, it is up to the
*COMMAND-LINE-ARGUMENTS-READER*
object to identify options among the command line arguments.
- Multiple encounters
The last part of option declaration is specifying what to do when the same option is found more than once on the command line. This behaviour can be customised using the declarationREDUCING-POLICY
.(define-program program (&options (file file-value) (output-file output-file-value)) (declare (reducing-policy append-policy file output-file)))
By default, if an option appears more than once, an error is produced. However, a number of other policies are provided
TOGGLE-POLICY
- Negates the previous value. Useful for no parameter options.
COUNT-POLICY
- Count the number of times the switch appears on the command line.
USE-FIRST-POLICY
- Use the first value read from the command line.
USE-LAST-POLICY
- Use the last value read from the command line.
APPEND-POLICY
- Concatenates values to form a list.
ERROR-POLICY
- Signals an error.
User supplied reducing functions can be used by specifying the symbol name of the function. The function supplied must adhere to the following policies:
- Accept 0 arguments
- The value returned will be the value used when the argument is NOT present on the command line. (Only for no parameter option arguments)
- Accept 1 argument
- The first time the option argument is encountered on the command line. (Not applicable for no parameter option arguments)
- Accept 2 arguments
- When the option argument is encountered again on the command line.
4.1.2 Arguments
Anything found on the command line that is not an option, is an
argument. All argument declarations occur after the &ARGUMENTS
symbol.
(define-program program (&options help &arguments filename) (cond (help (print-help)) (filename (perform-action filename)) (t (print-help) (error "Invalid usage."))))
The example above defines an argument FILENAME
. The value of
argument symbols will be either NIL
or non NIL
depending on
whether the argument is present on the command line or not.
By default, the value of argument symbols will be of type
string. Automatic conversion to other types can be performed using the
CONVERSION-FUNCTION
declaration.
(define-program program (&options help &arguments how-many-iterations) (declare (conversion-function integer how-many-iterations)))
4.1.3 Other Arguments
Other arguments accumulate all non processed command line arguments passed to the program.
(define-program program (&options help &arguments how-many-iterations &others files))
String conversion for rest arguments can be specified using
the CONVERSION-FUNCTION
.
5 Defining a Dispatcher
A dispatcher program is one in which the operation to be performed is
determined from the command line. For example, the program git
has a
number of commands which are all accessed via git
$ git init $ git status $ git reset
and so on. The goal of the dispatcher program is to easily define these types of programs.
The key difference between a dispatcher program and the program defined in the previous section is in the handling of the command line options. Any option occurring before an argument is an option to the dispatcher and any option occurring after an argument is a option to the dispatched program.
An example dispatcher program can be defined as follows
(define-dispatcher-program git (&options help &arguments command &others others) (cond ((or help (null command)) (print-usage)) (command (alexandria:switch (command :test #'string-equal) ("init" (program-apply 'git/init others)) ("commit" (program-apply 'git/commit others)) (t (error "Don't know how to perform command ~A" command))))))
The declarations IDENTIFIERS
, CONVERSION-FUNCTION
and
REDUCING-POLICY
can be used within the DEFINE-DISPATCHER-PROGRAM
form as well.
6 Testing a Program
A defined program can be tested by using the functions
PROGRAM-FUNCALL
and PROGRAM-APPLY
. The arguments passed to these
functions must be of type string. The identification of options and
non option arguments is handled by the object bound to
*COMMAND-LINE-ARGUMENTS-READER*
.
(define-program my-program (&options help (file file-value) &arguments what-to-do) (list help file-value what-to-do)) (setf *command-line-arguments-reader* 'gnu-style) (program-funcall 'my-program "hello-there") ; => (NIL NIL "hello-there") (program-funcall 'my-program "--help") ; => (T NIL NIL) (program-funcall 'my-program "--file=good-program") ; => (NIL "good-program" NIL)
The function PROGRAM-APPLY
is to PROGRAM-FUNCALL
as the Common
Lisp function APPLY
is to FUNCALL
.
If you want to test the program without considering how options are
read from the command line, the functions PROGRAM-FUNCALL-WITH-ALIST
and PROGRAM-FUNCALL-WITH-PLIST
can be used.
(program-funcall-with-alist 'my-program '((help t))) (program-funcall-with-plist 'my-program 'help t) (program-funcall-with-alist 'my-program '((file t) (file-value "input.txt"))) (program-funcall-with-plist 'my-program '(file t file-value "input.txt"))
7 Reading the command line
The object bound to the symbol *COMMAND-LINE-ARGUMENTS-READER*
represents the method in which the command line arguments are
identified. As of writing, GNU-STYLE
is the only implemented style
of identifying options and arguments from strings.
The GNU style uses the following templates for options
-h
- A short option with identifier
h
. --help
- A long option with identifier
help
. --debug=1
- A long option with identifier
debug
and parameter1
. --file input.txt
- A long option with identifier
file
and parameterinput.txt
. Valid for mandatory parameter options only. -f input.txt
- A short option with identifier
f
and parameterinput.txt
. Valid for mandatory parameter options only. --
- Terminate option processing. i.e. All options found after this delimiter will be treated as non option arguments.
8 Generating a program
One of the features of the LISP-EXECUTABLE
library is that it is
possible to generate an executable from a command line program
definition.
The function provided to do this is CREATE-EXECUTABLE
.
(define-program my-program (&options help) (cond (help (format t "Help has arrived.")) (t (format t "You are doomed.")))) (create-executable 'my-program "/tmp/my-program" :asdf-system "system-containing-my-program")
The keyword :asdf-system
is important as CREATE-EXECUTABLE
uses
this argument to initialize a new lisp machine in order to create the
program. The need for a separate process is that the machine specific
function equivalent to SAVE-LISP-MACHINE
on some lisps actually
kills the currently executing process. e.g. SB-EXT:SAVE-LISP-AND-DIE
on SBCL.
9 ASDF Build Integration
The building of an executable can also be specified in the ASDF system
definition by using the LISP-EXECUTABLE:EXECUTABLE
ASDF component.
(eval-when (:compile-toplevel :load-toplevel :execute) (asdf:load-system "lisp-executable")) (defsystem lisp-executable-example :author "Mark Cox" :serial t :components ((:modules "example/" :serial t :components ((:file "main") (lisp-executable:executable "example-program" :program ("LISP-EXECUTABLE.EXAMPLE" "EXAMPLE-PROGRAM"))))))
The keyword argument :PROGRAM
contains the symbol path to the
program. From the above example, an executable will be created in the
directory "example/" with the name "example-program". When the
executable is executed, it will invoke the program
LISP-EXECUTABLE-EXAMPLE::EXAMPLE-PROGRAM
.
To build the executable, you perform the
LISP-EXECUTABLE:CREATE-EXECUTABLES-OP
operation on the system.
(asdf:oos 'lisp-executable:create-executables-op "lisp-executable-example")
10 Conversion Functions
As mentioned previously, you can specify a function to convert the string found on the command line to its expected type within the program. For convenience, there are some built in conversion functions that use the lisp reader with type checking and a coercion. These are
CL:NUMBER
CL:REAL
CL:FLOAT
CL:SINGLE-FLOAT
CL:DOUBLE-FLOAT
CL:RATIONAL
CL:INTEGER
CL:FIXNUM
CL:UNSIGNED-BYTE
CL:SIGNED-BYTE
CL:RATIO
The compound type specifiers for the above can also be specified, for
example, the argument HOW-MANY-TIMES
should be greater than equal to
0
.
(define-program counter (&options (how-many-times how-many-times-value)) (declare (conversion-function (integer 0) how-many-times)))
Another special built in conversion function is CL:KEYWORD
, which
converts the string in to a keyword
(define-program file-processor (&options (if-exists if-exists-value)) (declare (conversion-function keyword if-exists) (type (member nil :error :supersede) if-exists-value)))
11 Testing the library
The lisp-executable library outlined above is tested using the
LISP-EXECUTABLE-TESTS
system. These tests can be executed by issuing
(asdf:test-system "lisp-executable")
The tests require the LISP-UNIT
unit testing library (version 0.9.1
and above). The version available from QUICKLISP
should always be
sufficient.
12 Acknowledgments
Thank you to the people who develop Solarized CSS and Org mode.
Lastly, big thanks to the Lisp community for all their excellent work.