To determine which version of the Irix operating system i(OS) you are running on a Silicon Graphics, Inc. (SGI) system, use the "uname -R" command.
The second of the two values, minus the trailing character, is the actual version number, e.g. 6.5.19 above. SGI calls this value the "extended" version number.
The "-R" option to the uname command is unique to Irix systems. See the Irix uname manpage for further information on version numbering and options for the uname command on Irix systems.