Creating Sigma Web Framework advanced applications

This section continues the discussion of creating Sigma Framework applications. More advanced, interactive applications are discussed, including how to create interactive forms and pass CGI arguments to programs via "Post" commands.

Sigma provides an easy framework for creating these types of applications, and provides facilities and services to pass CGI arguments and HTTP "Post" data to subprograms launched by the "Web.exe" interface. Using these facilities, programmers can create stand-alone applications that work outside of Sigma, or integrated applications that leverage the "sigma.lib" functions of the Framework programmer SDK.

This section provides a discussion of the advanced features, and an introduction to the Sigma.lib programmer API. It contains additional information that will be of interest to script authors and intermediate programmers.

Additional information on the Sigma API, including the "sigcmd.exe" program and the "runsql.exe" program, is available in the Appendices to this document, including a description of all configuration files on the system.

Additional notes

  • The Sigma framework contains specific elements needed to receive posted arguments, required to make forms and more advanced screen systems.
  • When a form is posted, the input form names and values appear in the temporary file given by the environmental variable S_POST. This file contains a list of input names and values that are easily parsed and read by any program.
  • The S_WIN32_POST environmental variable is identical to the S_POST variable, except that the pathname to the temporary file is represented as back slashes rather than forward slashes. Both of these environmental variables point to the same file.
  • The S_ACCESS environmental variable contains the currently defined access of the logged in Sigma user, and can be used to limit access and execution of screens within the Sigma Framework.
  • The "sigcmd.exe" program contains various utilities, documented in Sigcmd-exe-utility-program, that make the encoding and encryption of URL data easy. The executable corresponds to C++ language function calls available to programmers in the "sigma.lib" library, documented in Sigma-dll-and-Sigma-lib-program-files.
  • The sigcmd.exe SG_form command (and SG_form() function call) creates a form HTML tag, where the form action payload is encrypted. 
  • The sigcmd.exe SG_link command (and SG_link() function call creates a hyperlink anchor, possibly containing additional arguments passed to the target, where the URL payload is encrypted. 
  • When using the SG_link function, semicolons, and not ampersands MUST separate the command arguments passed to the target program. Each argument is appended to the target, separated by a ";" character.
  • It is the responsibility of the programmer to close the form and anchor tags generated by the SG_form and SG_link calls.

Although developers are free to make liberal use of batch files, in practice most systems will make use of other, more robust programming languages such as Perl, PHP, Ruby, Java, or .NET. In particular, the Sigma framework contains a comprehensive C / C++ programming API, which is reflected in the "sigcmd.exe" utility.

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