The core Racket run-time system is available in two main variants:
Racket, which provides the primitives libraries on which racket/base is implemented. On Unix and Mac OS X, the executable is called racket. On Windows, the executable is called Racket.exe.
GRacket, which is a GUI variant of racket to the degree that the system distinguishes them. On Unix, the executable is called gracket, and single-instance flags and X11-related flags are handled and communicated specially to the racket/gui/base library. On Windows, the executable is called GRacket.exe, and it is a GUI application (as opposed to a console application) that implements single-instance support. On Mac OS X, the gracket script launches GRacket.app.
On start-up, the top-level environment contains no bindings—
The first action of Racket or GRacket is to initialize current-library-collection-paths to the result of (find-library-collection-paths pre-extras extras), where pre-extras is normally null and extras are extra directory paths provided in order in the command line with -S/--search. An executable created from the Racket or GRacket executable can embed paths used as pre-extras.
Racket and GRacket next require racket/init and racket/gui/init, respectively, but only if the command line does not specify a require flag (-t/--require, -l/--lib, or -u/--require-script) before any eval, load, or read-eval-print-loop flag (-e/--eval, -f/--load, -r/--script, -m/--main, or -i/--repl). The initialization library can be changed with the -I configuration option. The configure-runtime submodule of the initialization library or the 'configure-runtime property of the initialization library’s language is used before the library is instantiated; see Language Run-Time Configuration.
After potentially loading the initialization module, expression evals, files loads, and module requires are executed in the order that they are provided on the command line. If any raises an uncaught exception, then the remaining evals, loads, and requires are skipped. If the first require precedes any eval or load so that the initialization library is skipped, then the configure-runtime submodule of the required module or the 'configure-runtime property of the required module’s library language is used before the module is instantiated; see Language Run-Time Configuration.
After running all command-line expressions, files, and modules, Racket or GRacket then starts a read-eval-print loop for interactive evaluation if no command line flags are provided other than configuration options. If any command-line argument is provided that is not a configuration option, then the read-eval-print-loop is not started, unless the -i/--repl flag is provided on the command line to specifically re-enable it. In addition, just before the command line is started, Racket loads the file (find-system-path 'init-file) and GRacket loads the file (find-graphical-system-path 'init-file) is loaded, unless the -q/--no-init-file flag is specified on the command line.
Finally, before Racket or GRacket exits, it calls the procedure that is the current value of executable-yield-handler in the main thread, unless the -V/--no-yield command-line flag is specified. Requiring racket/gui/base sets this parameter call (racket 'yield).
The default exit status for a Racket or GRacket process is non-zero if an error occurs during a command-line eval (via -e, etc.), load (via -f, -r, etc.), or require (via --l, -t, etc.), but only when no read-eval-print loop is started. Otherwise, the default exit status is 0.
The vector '#(racket/language-info get-info #f) is suitable for attaching to a module as its language info to get the same language information as the racket/base language.
The vector #(racket/runtime-config configure #f) is suitable as a member of a list of runtime-configuration specification (as returned by a module’s language-information function for the key 'configure-runtime) to obtain the same runtime configuration as for the racket/base language.
The Racket and GRacket executables recognize the following command-line flags:
File and expression options:
-f ‹file› or --load ‹file› : loads ‹file›; if ‹file› is "-", then expressions are read and evaluated from standard input.
-r ‹file› or --script ‹file› : loads ‹file› Despite its name, --script is not usually used for Unix scripts. See Scripts for more information on scripts. as a script. This flag is like -t ‹file› plus -N ‹file› to set the program name and -- to cause all further command-line elements to be treated as non-flag arguments.
-u ‹file› or --require-script ‹file› : requires ‹file› as a script; This flag is like -t ‹file› plus -N ‹file› to set the program name and -- to cause all further command-line elements to be treated as non-flag arguments.
-k ‹n› ‹m› ‹p› : Loads code embedded in the executable from file position ‹n› to ‹m› and from ‹m› to ‹p›. (On Mac OS X, ‹n›, ‹m›, and ‹p› are relative to a __PLTSCHEME segment in the executable.) The first range is loaded in every new place, and any modules declared in that range are considered predefined in the sense of module-predefined?. This option is normally embedded in a stand-alone binary that also embeds Racket code.
-m or --main : Evaluates a call to main as bound in the top-level environment. All of the command-line arguments that are not processed as options (i.e., the arguments put into current-command-line-arguments) are passed as arguments to main. The results of the call are printed via current-print.
The call to main is constructed as an expression (main arg-str ...) where the lexical context of the expression gives #%app and #%datum bindings as #%plain-app and #%datum, but the lexical context of main is the top-level environment.
-i or --repl : Runs an interactive read-eval-print loop, using either read-eval-print-loop (Racket) or graphical-read-eval-print-loop (GRacket) after showing (banner) and loading (find-system-path 'init-file). In the case of Racket, (read-eval-print-loop) is followed by (newline). For GRacket, supply the -z/--text-repl configuration option to use read-eval-print-loop (and newline) instead of graphical-read-eval-print-loop.
-v or --version : Shows (banner).
-c or --no-compiled : Disables loading of compiled byte-code ".zo" files, by initializing current-compiled-file-paths to null. Use judiciously: this effectively ignores the content of all "compiled" subdirectories, so that any used modules are compiled on the fly—
even racket/base and its dependencies— which leads to prohibitively expensive run times.
-q or --no-init-file : Skips loading (find-system-path 'init-file) for -i/--repl.
-I ‹path› : Sets (lib "‹path›") as the path to require to initialize the namespace, unless namespace initialization is disabled. Using this flag can effectively set the language for the read-eval-print loop and other top-level evaluation.
-X ‹dir› or --collects ‹dir› : Sets ‹dir› as the path to the main collection of libraries by making (find-system-path 'collects-dir) produce ‹dir›. If ‹dir› is an empty string, then (find-system-path 'collects-dir) returns ".", but current-library-collection-paths is initialized to the empty list, and use-collection-link-paths is initialized to #f.
-S ‹dir› or --search ‹dir› : Adds ‹dir› to the default library collection search path after the main collection directory. If the -S/--dir flag is supplied multiple times, the search order is as supplied.
-R ‹paths› or --compiled ‹paths› : Sets the initial value of the current-compiled-file-roots parameter, overriding any PLTCOMPILEDROOTS setting. The ‹paths› argument is parsed in the same way as PLTCOMPILEDROOTS (see current-compiled-file-roots).
-G ‹dir› or --config ‹dir› : Sets the directory that is returned by (find-system-path 'config-dir).
-A ‹dir› or --addon ‹dir› : Sets the directory that is returned by (find-system-path 'addon-dir).
-U or --no-user-path : Omits user-specific paths in the search for collections, C libraries, etc. by initializing the use-user-specific-search-paths parameter to #f.
-N ‹file› or --name ‹file› : sets the name of the executable as reported by (find-system-path 'run-file) to ‹file›.
-j or --no-jit : Disables the native-code just-in-time compiler by setting the eval-jit-enabled parameter to #f.
-d or --no-delay : Disables on-demand parsing of compiled code and syntax objects by setting the read-on-demand-source parameter to #f.
-W ‹levels› or --warn ‹levels› : Sets the logging level for writing events to the original error port. The possible ‹level› values are the same as for the PLTSTDERR environment variable. See Logging for more information.
-L ‹levels› or --syslog ‹levels› : Sets the logging level for writing events to the system log. The possible ‹level› values are the same as for the PLTSYSLOG environment variable. See Logging for more information.
If at least one command-line argument is provided, and if the first one after any configuration option is not a flag, then a -u/--require-script flag is implicitly added before the first non-flag argument.
If no command-line arguments are supplied other than configuration options, then the -i/--repl flag is effectively added.
For GRacket on Unix, the follow flags are recognized when they appear at the beginning of the command line, and they count as configuration options (i.e., they do not disable the read-eval-print loop or prevent the insertion of -u/--require-script):
-geometry ‹arg›, -bg ‹arg›, -background ‹arg›, -fg ‹arg›, -foreground ‹arg›, -fn ‹arg›, -font ‹arg›, -iconic, -name ‹arg›, -rv, -reverse, +rv, -selectionTimeout ‹arg›, -synchronous, -title ‹arg›, -xnllanguage ‹arg›, or -xrm ‹arg› : Standard X11 arguments that are mostly ignored but accepted for compatibility with other X11 programs. The -synchronous flag behaves in the usual way.
-singleInstance : If an existing GRacket is already running on the same X11 display, if it was started on a machine with the same hostname, and if it was started with the same name as reported by (find-system-path 'run-file)—
possibly set with the -N/--name command-line argument— then all non-option command-line arguments are treated as filenames and sent to the existing GRacket instance via the application file handler (see application-file-handler).
Similarly, on Mac OS X, a leading switch starting with -psn_ is treated as a special configuration option. It indicates that Finder started the application, so the current input, output, and error output are redirected to a GUI window.
Multiple single-letter switches (the ones preceded by a single -) can be collapsed into a single switch by concatenating the letters, as long as the first switch is not --. The arguments for each switch are placed after the collapsed switches (in the order of the switches). For example,
-ifve ‹file› ‹expr›
-i -f ‹file› -v -e ‹expr›
are equivalent. If a collapsed -- appears before other collapsed switches in the same collapsed set, it is implicitly moved to the end of the collapsed set.
Extra arguments following the last option are available from the current-command-line-arguments parameter.
A module can have a configure-runtime submodule that is dynamic-required before the module itself when a module is the main module of a program. Normally, a configure-runtime submodule is added to a module by the module’s language (i.e., by the #%module-begin form among a module’s initial bindings).
Alternatively or in addition, an older protocol is in place. When a module is implemented using #lang, the language after #lang can specify configuration actions to perform when a module using the language is the main module of a program. The language specifies run-time configuration by
having the function indicated by the 'module-language syntax property recognize the 'configure-runtime key, for which it returns a list of vectors; each vector must have the form (vector mp name val) where mp is a module path, name is a symbol, and val is an arbitrary value; and
A 'configure-runtime query returns a list of vectors, instead of directly configuring the environment, so that the indicated modules to be bundled with a program when creating a stand-alone executable; see raco exe: Creating Stand-Alone Executables in raco: Racket Command-Line Tools.