This command will execute the code in the file myprog.sl. Note that the files do not have to end in ".sl", but it is a useful idiom. If the contents of myprog.sl were:

  vmessage( "The time is %s.", time() );

then the output would look something like:

  unix% slsh myprog.sl
  The time is Fri Mar 19 11:28:40 2004

Both the vmessage() and time() functions are part of the S-Lang Run-Time Library, and so are available for use by slsh.

If you start a S-Lang script with the line

#!/usr/bin/env slsh

and set it to be an executable, then you can run the script without having to explicitly call slsh. So if the file myprog.sl looked like:

  #!/usr/bin/env slsh
  vmessage( "The time is %s.", time() );

then the script could be run by just saying:

  unix% ./myprog.sl
  The time is Fri Mar 19 11:28:40 2004.

assuming that

chmod u+x myprog.sl

had previously been called. The following examples will use this method.

Code that uses CIAO modules can also be run using slsh. All that needs to be done is to load the required modules before using any functions they define. In the following example we use the region module to calculate the area of a simple region.

  unix% cat reg.sl
  #!/usr/bin/env slsh
  require("region");
  variable reg = regParse( "circle(4300.45,3274.22,60.3)" );
  vmessage( "The region area is: %7.2f", regArea(reg) );

which, when run, produces

  unix% ./reg.sl
  The region area is: 11423.11

Command-line arguments that are not recognised by slsh are made available to the S-Lang code via the __argc and __argv variables. These are analogous to the argc and argv variables of the main() routine in C code. We can use these variables to enhance the previous example to allow regions to be specified on the command line, rather than being written into the code.

  unix% cat reg2.sl
  #!/usr/bin/env slsh

  % check called correctly
  %
  if ( 2 != __argc ) {
    () = fprintf( stderr, "Usage: %s <region>\n", __argv[0] );
    exit(1);
  }

  require("region");

  % has the user given us a valid region?
  %
  variable reg = regParse( __argv[1] );
  if ( NULL == reg ) {
    () = fprintf( stderr, "Did not recognise %s as a region!\n",
                  __argv[1] );
    exit(1);
  }

  % print out the region area
  %
  vmessage( "The region area is: %7.2f", regArea(reg) );

The code has been enhanced to check that the correct number of arguments has been given and that the user-supplied argument is recognised as a region. As an example of its use:

  unix% ./reg2.sl
  Usage: ./reg2.sl <region>
  unix% ./reg2.sl "circle(4200,3200,60.3)"
  The region area is: 11423.11
  unix% ./reg2.sl "annulus(4200,3200,10,60.3)"
  The region area is: 11108.95