This package uses the (La)TeX extension -shell-escape to establish whether the document is being processed on a Windows or on a Unix-like system (Mac OS X, Linux, etc.), or on Cygwin (Unix environment over a windows system).

Booleans provided are:

• \ifwindows ,
• \iflinux ,
• \ifmacosx and
• \ifcygwin .

The package also preserves the output of uname on a Unix-like system, which may be used to distinguish between various classes of Unix systems.