Chapter 17

Running MzScheme

The stand-alone version of MzScheme accepts a number of command-line flags.

MzScheme accepts the following flags:

• Startup file and expression flags:

  •    -e expr or --eval expr : Evaluates expr after MzScheme starts.

  •    -f file or --load file : Loads file after MzScheme starts.

  •    -d file or --load-cd file : Uses load/cd to load file after MzScheme starts.

  •    -t file or --require file : Requires file after MzScheme starts.

  •    -F or --Load : Loads each remaining argument as a file after MzScheme starts.

  •    -D or --Load-cd : Loads each remaining argument as a file using load/cd after MzScheme starts.

  •    -T or --Require : Requires each remaining argument as a file after MzScheme starts.

  •    -l file or --mzlib file: Requires the MzLib library file after MzScheme starts.

  •    -L file collect : Requires the library file in the collection collect after MzScheme starts.

  •    -M collect : Requires the library collect.ss in the collection collect after MzScheme starts.

  •    -r file or --script file : Use this flag for MzScheme-based scripts. It mutes the startup banner printout, suppresses the read-eval-print loop, and loads file after MzScheme starts. No argument after file is treated as a flag. The -r or --script flag is a shorthand for -fmv-.

  •    -i file or --script-cd file : Same as -r file or --script file, except that the current directory is changed to file's directory before it is loaded. The -i or --script-cd flag is a shorthand for -dmv-.

  •    -u file or --require-script file : Same as -r file or --script file, except that file is required instead of loaded. The -u or --require-script flag is a shorthand for -tmv-.

  •    -w or --awk : Loads the awk.ss library after MzScheme starts.

  •    -k n m : Loads code embedded in the executable from file position n to m after MzScheme starts. This flag is useful for creating a stand-alone binary by appending code to the normal MzScheme executable. See PLT mzc: MzScheme Compiler Manual for more details.

  •    -C or --main : Like -r, then calls the function bound to main in the top-level environment. The argument to main is a list of immutable strings; the first string is the path of the file that was loaded, and the rest of the list contains leftover command-line arguments (the ones installed in current-command-line-arguments). The main function is called only if no previous evaluations or loads resulted in an uncaught exception.

• Initialization flags:

  •    -x or --no-lib-path : Suppresses the initialization of current-library-collection-paths (as described in Chapter 16).

  •    -q or --no-init-file : Suppresses loading the user's initialization file, as described below.

  •    -A or --no-argv : Suppresses the definition of argv and program, as described below.

• Language setting flags:

  •    -g or --case-sens : Creates an initial namespace where identifiers and symbols are case-sensitive.

  •    -s or --set-undef : Creates an initial namespace where set! will successfully mutate an undefined global variable (implicitly defining it).

• Miscellaneous flags:

  •    -- : No argument following this flag is used as a flag.

  •    -m or --mute-banner : Suppresses the startup banner text produced by -v.

  •    -v or --version : Suppresses the read-eval-print loop.

  •    -h or --help : Shows information about MzScheme's command-line flags and then exits, ignoring other flags.

  •    -p or --persistent : Catches the SIGDANGER (low page space) signal and ignores it (AIX only).

  •    -Rfile or --restore file : Restores a saved image (see section 14.8). Extra arguments after file are returned as a vector of strings to the continuation of the write-image-to-file call that created the image.

17.1  Flag Conventions

Extra arguments following the last flag are available from the current-command-line-arguments parameter (see section 7.7.1.6) as an immutable vector of immutable strings. The name used to start MzScheme is available from the find-system-path procedure (see section 11.3.1) using 'exec-file. In addition, unless -A is specified, the argument vector is put into the global variable argv, and the name used to start MzScheme is put into the global variable program as an immutable string.

Multiple single-letter flags (the ones preceded by a single dash) can be collapsed into a single flag by concatenating the letters, as long as the the first flag is not --. The arguments for each flag are placed after the collapsed flags (in the order of the flags). For example,

and

are equivalent. If a collapsed -- appears before other collapsed flags, it is implicitly moved to the end of the collapsed set.

17.2  Executable Name

If the MzScheme executable is given a name of the form scheme-dialect, then the command line is effectively prefixed with

The first actual command-line argument thus serves as a file to load. The file is loaded into a namespace that is initialized by the dialect-specific init.ss library. The loaded file should define main, which is called with command-line arguments -- starting with the loaded file name -- as a list of immutable strings.

17.3  Initialization

The current-library-collection-paths parameter is initialized (as described in Chapter 16) before any expression or file is evaluated or loaded, unless the -x or --no-lib-path flag is specified.

Unless the -q or --no-init-file flag is specified, a user initialization file is loaded after current-library-collection-paths parameter is initialized and before any other expression or file is evaluated or loaded. The path to the user initialization file is obtained from MzScheme's find-system-path procedure using 'init-file.

Expressions and files are evaluated and loaded in order that they are provided on the command line, including calls to main implied by --main, embeddings loaded by -k, and so on. If an uncaught exception occurs, the remaining expressions and files are skipped. The thread that loads the files and evaluates the expressions is the main thread. When the main thread terminates (or is killed), the MzScheme process exits.

After the command-line files and expressions are loaded and evaluated, the main thread calls read-eval-print-loop, unless the -v, --version, -r, --script, -i, or --script-cd flag is specified.

The exit status for the MzScheme process indicates an error if an error occurs evaluating or loading a command-line expression or file and read-eval-print-loop is not called afterwards, or if the default exit handler is called with an exact integer between 1 and 255.