Section: (1)
Updated: 04 March 2018
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slsh - Interpreter for S-Lang scripts  


slsh [ --help ] [ --version ] [ -g ] [ -n ] [ --init file ] [ --no-readline ] [ -e string ] [ -i ] [ -q, --quiet ] [ -t ] [ -v ] [ -|script-file args... ]



slsh is a simple program for interpreting S-Lang scripts. It supports dynamic loading of S-Lang modules and includes a readline interface for interactive use.  


Show a summary of options
Show slsh version information
Compile with debugging code, tracebacks, etc
Don't load the personal initialization file
--init file
Use this file instead of ~/.slshrc
Do not use a readline interface for the interactive mode
-e string
Execute ``string'' as S-Lang code.
Force interactive mode. Normally slsh will go into interactive mode if both stdin and stdout are attached to a terminal.
-q, --quiet
Startup quietly by not printing the version and copyright information.
Normally, slsh will call slsh_main if it is defined. This option prevents that from happening making it useful for checking for syntax error.
Show verbose loading messages. This is useful for seeing what files are being loaded.


Upon startup, the program will try to load slsh.rc as follows. If either SLSH_CONF_DIR or SLSH_LIB_DIR environment variables exist, then slsh will look look in the corresponding directories for slsh.rc. Otherwise it will look in:

$(prefix)/etc/ (as specified in the Makefile)





The slsh.rc file may load other files from slsh's library directory in the manner described below.

Once slsh.rc has been loaded, slsh will load $HOME/.slshrc if present. Finally, it will load the script specified on the command line. If the name of the script is -, then it will be read from stdin. If the script name is not present, or a string to execute was not specified using the -e option, then slsh will go into interactive mode and read input from the terminal. If the script is present and defines a function called slsh_main, that function will be called.  


When a script loads a file via the built-in evalfile function or the require function (autoloaded by slsh.rc), the file is searched for along the SLSH_PATH as specified in the Makefile. An alternate path may be specified by the SLSH_PATH environment variable.

The search path may be queried and set during run time via the get_slang_load_path and set_slang_load_path functions, e.g.,

   set_slang_load_path ("/home/bill/lib/slsh:/usr/share/slsh");


When slsh is invoked without a script or is given the -i command line argument, it will go into into interactive mode. In this mode, the user will be prompted for input. The program will leave this mode and exit if it sees an EOF (Ctrl-D) or the user exits by issuing the quit command.

If an uncaught exception occurs during execution of a command, the error message will be shown and the user will be prompted for more input.

Any objects left on the stack after a command will be printed and the stack cleared. This makes interactive mode useful as a calculator, e.g.,

     slsh> 3*10;
     slsh> x = [1:20];
     slsh> sum (sin(x)-cos(x));
     slsh> quit;
Note that in this mode, variables are automatically declared.

The interactive mode also supports command logging. Logging is enabled by the start_log function. The stop_log function will turn off logging. The default file where logging information will be written is slsh.log. An alternative may be specified as an optional argument to the start_log function:

     slsh> start_log;
     Logging input to slsh.log
     slsh> stop_log;
     slsh> start_log("foo.log");
     Logging input to foo.log
     slsh> stop_log;
     slsh> start_log;
     Logging input to foo.log

Similarly, the save_input function may be used to save the previous input to a specified file:

     slsh> save_input;
     Input saved to slsh.log
     slsh> save_input ("foo.log");
     Input saved to foo.log

As the above examples indicate, lines must end in a semicolon. This is a basic feature of the language and permits commands to span multiple lines, e.g.,

     slsh> x = [
     slsh> sum(x);
For convenience some users prefer that commands be automatically terminated with a semicolon. To have a semicolon silently appended to the end of an input line, put the following in $HOME/.slshrc file:

    #ifdef __INTERACTIVE__
    slsh_append_semicolon (1);

The interactive mode also supports shell escapes. To pass a command to the shell, prefix it with !, e.g.,

    slsh> !pwd
    slsh> !cd doc/tm
    slsh> !pwd

Finally, the interactive mode supports a help and apropos function:

    slsh> apropos list
    apropos list ==>
    slsh> help list_append

       Append an object to a list

       list_append (List_Type, object, Int_Type nth)
For convenience, the help and apropos functions do not require the syntactic constraints of the other functions.  


By default, slsh is built to use the S-Lang readline interface, which includes a customizable command completion and a history mechanism. When slsh (or any S-Lang application that makes use of this feature) starts in interactive mode, it will look for a file in the user's home directory called .slrlinerc and load it if present. This file allows the user to customize the readline interface and enable the history to be saved between sessions. As an example, here is a version of the author's .slrlinerc file:

     % Load some basic functions that implement the history mechanism
     () = evalfile ("rline/slrline.rc");
     % The name of the history file -- expands to .slsh_hist for slsh
     RLine_History_File = "$HOME/.${name}_hist";

     % Some addition keybindings.  Some of these functions are defined
     % in rline/, loaded by rline/slrline.rc
     rline_unsetkey ("^K");
     rline_setkey ("bol",   "^B");
     rline_setkey ("eol",   "^E");
     rline_setkey (&rline_kill_eol,  "^L");
     rline_setkey (&rline_set_mark,  "^K^B");
     rline_setkey (&rline_copy_region, "^Kk");
     rline_setkey (&rline_kill_region, "^K^V");
     rline_setkey (&rline_yank,  "^K^P");
     rline_setkey ("redraw",   "^R");

     #ifexists rline_up_hist_search
     % Map the up/down arrow to the history search mechanism
     rline_setkey (&rline_up_hist_search, "\e[A");
     rline_setkey (&rline_down_hist_search, "\e[B");

     #ifexists rline_edit_history
     rline_setkey (&rline_edit_history, "^Kj");

     % Add a new function
     private define double_line ()
        variable p = rline_get_point ();
        variable line = rline_get_line ();
        rline_eol ();
        variable pend = rline_get_point ();
        rline_ins (line);
        rline_set_point (pend + p);
    rline_setkey (&double_line,  "^K^L");


Several useful example scripts are located in $prefix/share/slsh/scripts/, where $prefix represents the slsh installation prefix (/usr, /usr/local,...). These scripts include:

A script that runs the S-Lang debugger.
Reports the size of a jpeg file.
A shell for browsing an SVN repository.


The principal author of slsh is John E. Davis <>. The interactive mode was provided by Mike Noble. The S-Lang library upon which slsh is based is primarily the work of John E. Davis with help from many others.

This manual page was originally written by Rafael Laboissiere for the Debian system (but may be used by others).

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 any later version published by the Free Software Foundation.

On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL