cnet's runtime environment

When initially configured and compiled, cnet employs a number of string constants to define and constrain its execution. While it is anticipated that these "compiled-in" defaults will be reasonable, there are occasions when you may wish to change one without having to recompile all code.

At runtime, cnet honours a number of Unix/Linux environment variables that may override cnet's default behaviour. Running cnet with its -v option will report the environment values that are being used (along with much other information).

Depending on which Unix/Linux shell you use (type  echo $SHELL  to find out), environment variables may be set in one of two ways:

  • for sh, bash, ksh, or zsh:
    CNETPATH="/usr/local/cnetlib" ; export CNETPATH

  • for csh:
    setenv CNETPATH="/usr/local/cnetlib"

variable name description
CNETPATH The value of CNETPATH provides a colon-separated list of directory names where cnet will search for the <cnet.h> header file when compiling C protocol files. CNETPATH is also used to locate the Tcl/Tk source file (see CNETTCLTK, below), the GIF images displayed on the simulation map, and any extension modules specified with the -x option.
CNETCPP The value of CNETCPP provides the full pathname of the C preprocessor used to preprocess cnet topology files (if necessary). If gcc is being used as the preprocessor, it will be invoked with its -E option to preprocess the topology files.
CNETCC The value of CNETCC provides the full pathname of the C compiler used to compile the C99 protocol files. If gcc is being used as the compiler, it will be invoked with its -std=c99 option to compile the source files.
CNETLD The value of CNETLD provides the full pathname of the program used to link one or more object files to produce the final executable protocol.
CNETFILEEXT The value of CNETFILEEXT provides the filename extension of cnet's (executable) shared object files. By default, this is ".cnet"
CNETTCLTK The CNETTCLTK environment variable provides the filename of the Tcl/Tk source file that defines the look of cnet's graphical interface. If the specified filename does not contain a slash (/) character, the file is sought via the value of CNETPATH (see above). Setting CNETTCLTK saves you from having to invoke cnet with its -F option. By default, this is "cnet.tcl"
DISPLAY cnet uses Tcl/Tk under the X-window system on Unix/Linux to provide its graphical interface (not employed on Mac-OSX). Setting the DISPLAY environment variable permits cnet's graphical interface to be redirected to another display/screen.

 cnet v3.3.3, written by
 Last modified: Tue Oct 13 1:07PM 2015