command-line-arguments

Arguments: &key application

This function and its relatives, command-line-argument and command-line-argument-count, provide information about the command line that invoked Allegro CL. Their precise behavior depends on the value of the application keyword argument.

The command line includes the following, in the order specified:

1. The executable name. This may include directory information (i.e. /usr/local/acl/mlisp) or may not (just mlisp).
2. Command-line arguments prefixed by a +. these are used on Windows only.
3. command-line arguments prefixed by a - and, when appropriate, the values of those arguments.
4. the special marker -- (a double dash).
5. any arguments whatsoever that follow the double-dash.

See Command line arguments in startup.htm for a list of command-line arguments accepted by Allegro CL.

When the value of the :application keyword argument is true

The application arguments are the executable name (number 1 in the list above) and the ones which follow the double dash (number 5 in the list above). Consider that those arguments are collected as strings in a list called the list-of-application-arguments. When application is true (it defaults to t), the command-line argument information functions behave as follows:

• command-line-argument with argument n returns the (0 based) nth element of the list-of-application-arguments. It is an error to specify a value for n equal to or greater than the length of list-of-application-arguments.
• command-line-arguments returns the list list-of-application-arguments.
• command-line-argument-count returns the length of the list list-of-application-arguments.

Examples when :application is true

;;  Lisp was started on UNIX with the command line
;;  (we assume the mlisp executable is in a directory
;;  included in the PATH environment variable):
% mlisp -qq -- init 5 safe

(sys:command-line-argument-count :application t)
  RETURNS 4
(sys:command-line-argument-count)  ;; :application defaults to T
  RETURNS 4
(sys:command-line-arguments)
  RETURNS ("mlisp" "init" "5" "safe")
;;  or perhaps (/usr/local/acl70/mlisp init 5 safe)
;;  assuming mlisp is in /usr/local/acl70/: the directory
;;  may or may not be included.
(sys:command-line-argument 0)
  RETURNS "mlisp"  ;; or perhaps "/usr/local/acl70/mlisp"
(sys:command-line-argument 1)
  RETURNS "init"
(sys:command-line-argument 2)
  RETURNS "5"
(sys:command-line-argument 3)
  RETURNS "safe"
(sys:command-line-argument 4)
  ERROR    ;;  the first argument to sys:command-line-argument
           ;;  must be less than the number of arguments
           ;;  as returned by sys:command-line-argument-count

;;  Lisp was started on WINDOWS with the command line
% mlisp.exe +co -qq -- init 5 safe
;;  The values returned by the command-line argument functions are the
;;  same as on UNIX (except "mlisp.exe" or 
;;  "C:\\Program Files\\acl70\\mlisp.exe" replaces "mlisp" or 
;;  "/usr/local/acl70/mlisp".

When the value of the :application keyword argument is nil

All arguments except those beginning with + are considered command-line arguments by these functions when application is nil. That includes the executable name (number 1 in the list above), the - arguments and their values (number 3 in the list above), the double dash (number 4 in the queue above), and arguments which follow the double dash (number 5 in the list above). Consider that those arguments are collected as strings in a list called the list-of-arguments. When application is nil, the command-line argument information functions behave as follows:

• command-line-argument with argument n returns the (0 based) nth element of the list-of-arguments. It is an error to specify a value for n equal to or greater than the length of list-of-arguments. Note the + arguments are ignored and will not be returned for any value of n. The double dash, if present, is considered and will be returned for some value of n.
• command-line-arguments returns the list list-of-arguments. Note the + arguments are ignored and thus not included, while the double dash, if present, is included.
• command-line-argument-count returns the length of the list list-of-arguments. Note the + arguments are ignored and thus not counted, while the double dash is counted as an argument.

Examples when :application is nil

;;  Lisp was started on UNIX with the command line
;;  (we assume the mlisp executable is in a directory
;;  included in the PATH environment variable):
% mlisp -qq -- init 5 safe

(sys:command-line-argument-count :application nil)
  RETURNS 6
(sys:command-line-arguments :application nil)
  RETURNS ("mlisp" "-qq" "--" "init" "5" "safe")
;;  or perhaps (/usr/local/acl70/mlisp -qq -- init 5 safe)
;;  assuming mlisp is in /usr/local/acl70/: the directory
;;  may or may not be included.
(sys:command-line-argument 0)
  RETURNS "mlisp"  ;; or perhaps "/usr/local/acl70/mlisp"
(sys:command-line-argument 1)
  RETURNS "-qq"
(sys:command-line-argument 2)
  RETURNS "--"
(sys:command-line-argument 3)
  RETURNS "init"
(sys:command-line-argument 4)
  RETURNS "5"
(sys:command-line-argument 5)
  RETURNS "safe"
(sys:command-line-argument 6)

  ERROR    ;;  the first argument to sys:command-line-argument
           ;;  must be less than the number of arguments
           ;;  as returned by sys:command-line-argument-count

;;  Lisp was started on WINDOWS with the command line
% mlisp.exe +co -qq -- init 5 safe
;;  The values returned by the command-line argument functions are the
;;  same as on UNIX (except "mlisp.exe" or 
;;  "C:\\Program Files\\acl70\\mlisp.exe" replaces "mlisp" or 
;;  "/usr/local/acl70/mlisp". The command-line argument functions
;;  always ignore the + arguments.

Anomolies when :application is true

If the Allegro CL image was created with dumplisp (or build-lisp-image or generate-application) with the ignore-command-line-arguments argument true (the default is nil), then arguments are not processed by Allegro CL when it starts up and all arguments (regardless of whether a `--' appears on the command line) are handled by these functions and the value of the application keyword argument has no effect.

Anomolies when :application is nil

The system may tack on arguments in addition to those you specified. In particular, when using the Emacs-Lisp interface, the arguments -e (start-emacs-lisp-interface t) may be added (to start in connection between Lisp and Emacs). Do not be surprised is you see these additional arguments. The system never adds arguments after a -- (double dash).

The path of the executable

Note that the zeroth argument is the name of the executable as entered in the command line, with or without path information. That is, the 0th argument may be, say, "mlisp" (without path information) or may be, say, "/usr/local/acl70/mlisp" (with path information). If path information is not provided and you need it, evaluating

(translate-logical-pathname (concatenate 'string "sys:"
(sys:command-line-argument 0)))

will typically work. (But that form signals an error when path information is provided.)

Uses of command-line arguments

You may use this information as you see fit. One possible use, for example, is to have some function defined and run (perhaps in the initialization file .clinit.cl) which takes some action (such as loading specific files) based on the values of the arguments. Recall again that + arguments are ignored and so their presence or absence cannot be used to affect behavior once Lisp has started.

This function and its relatives, command-line-argument and command-line-argument-count, provide information about the command line that invoked Allegro CL. Their behavior depends on the value of the application keyword argument. If the value of that argument is true (the default is t), only the executable name and arguments appearing after the first occurrence of `--', if there is one, in the command line are considered. If the value of application is nil, all arguments except those beginning with +, but including the `--', if there is one, are included.

As said above, + arguments, which are Windows specific and affect how the executable starts up on Windows, are discarded and not included in the information returned by this or any of the command-line argument functions.

See with-command-line-arguments, which is a macro that can be used to process command-line arguments. See Command line arguments in startup.htm for a list of command-line arguments accepted by Allegro CL.

command-line-argument returns the nth item on the command line. The item numbering is zero-based. If the value of the application keyword argument is true (the default), only the image name and the arguments after (and not including) the first occurrence of `--' in the command line are counted. If the value of application is nil, all arguments including the `--' are included. The executable name is argument 0. The argument is returned as a string.

command-line-arguments returns a list of strings indicating the arguments appearing on the command line used to start Allegro CL. If the value of the application keyword argument is true (the default), only the image name and the arguments appearing after the first occurrence of `--' are included. If the value of application is nil, all arguments including the `--', if there is one, are included.

command-line-argument-count returns the number of arguments on the Allegro CL command line. If the value of the application keyword argument is true (the default), only the image name and the arguments appearing after the first occurrence of `--', if there is one, are counted. If the value of application is nil, all arguments, including the `--', if there is one, are counted.

If the Allegro CL image was created with dumplisp (or build-lisp-image or generate-application) with the ignore-command-line-arguments argument true (the default is nil), then no argument is processed by Allegro CL when it starts up and all arguments (regardless of whether a `--' appears on the command line) are handled by these functions and the value of the application keyword argument has no effect.

The purpose of these functions is to allow you to customize the running of Lisp when the image is invoked. As a simple example, suppose you invoke Lisp (the example is on Windows) as follows:

mlisp.exe -qq -- foo -batch bar 

Here, mlisp.exe is the name of the Allegro CL executable. No -I argument is specified (but one is inserted by the system) so the image is mlisp.dxl in the same directory as mlisp.exe. Note first that Lisp will not run in batch mode since the -batch appears after `--'. However, no initialization file will be read since the -qq argument appears before the `--'.

Here is what the various command line functions return given that command line:

(sys:command-line-arguments :application nil)
[returns] ("C:\\Program Files\\acl70\\mlisp.exe" "-I" 
"C:\\Program Files\\acl70\\mlisp.dxl"
"-qq" "--"
"foo" "-batch" "bar")
(sys:command-line-argument 0) 
[returns] "C:\\Program Files\\acl70\\mlisp.exe"
(sys:command-line-argument 1)
[returns] "foo"
(sys:command-line-argument 3 :application nil)
[returns] "-qq"
(sys:command-line-arguments)
[returns] ("C:\\Program Files\\acl70\\mlisp.exe" 
"foo" "-batch" "bar")
(sys:command-line-argument-count) 
[returns] 4
(sys:command-line-argument-count :application nil) 
[returns] 8

Note that the zeroth argument is the name of the executable as entered in the command line, with or without (in the example, with) path information. If the path information is not provided and you need it, evaluating

(translate-logical-pathname (concatenate 'string "sys:"
(sys:command-line-argument 0)))

will typically work.

You may use this information as you see fit. One possible use, for example, is to have some function defined and run (perhaps in the initialization file .clinit.cl) which takes some action (such as loading specific files) based on the values of the arguments.

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.