To run irsim, you should add the line:
export PATH=/apps/magic6_5/irsim-9.5/src/irsim:$PATH to your .profile file.

Please read  simple irsim^* tutorial first to get an idea about irsim.

It is assumed that you extracted your files in magic using the extract command.

Use command ext2sim <filename.ext> to create a .sim file.

Copy the parameter file scmos2um.prm to your working directory. (Windows programs like ftp or notepad may add extra lines to this file.)

To ease simulation, you can write a command file. You should copy this to your working directory as well. You can modify it as needed. (Windows programs like ftp or notepad may add extra lines to this file.)

Now that you have the .sim file, parameter file and command file in your working directory, you can write:
irsim scmos2um.prm FILENAME.sim in the commad line.

The command prompt should change to irsim>

type iv (assuming command file name is iv.cmd) and analyzer window will open.

Type s to step forward.

For further commands, you can download user commands^**.

*http://www.stanford.edu/class/ee272/doc/faq/irsim/irsim_tut.txt
** http://www.ee.ucla.edu/~ee216a/lib/pdf/irsimman.pdf