Running Cactus

Cactus executables always run from a parameter file (that may be a specified as a command line argument taken from standard input), which specifies which thorns to use and sets the values of any parameters which are different from the default values. There is no restriction on the name of the parameter file, although it is conventional to use the file extension .par. Optional command line arguments can be used to customise runtime behaviour, and to provide information about the thorns used in the executable. The general syntax for running Cactus from a parameter file is then

./cactus_<config> <parameter file> [command line options]

or if the parameter file should be taken from standard input, the syntax includes a dash (``-'') on the command line like this:

./cactus_<config> [command line options] -

The remainder of this chapter covers all aspects for running your Cactus executable. These include: command-line options, parameter file syntax, understanding screen output, environment variables, and creating thorn documentation.