It absolutely is, and has been for a long time. I find it very hard to keep track of the various standards, but things got a lot simpler with v3 of the Single

It absolutely is, and has been for a long time. I find it very hard to keep track of the various standards, but things got a lot simpler with v3 of the Single Unix Specification, which is the same as POSIX 2001[0]. The problem is that SUS and POSIX only define a subset of what's wanted by most modern software and a subset of the tools people need to interacting with the system. It's a double-edged sword, though: if we always stuck to what was common to all Unix-like systems, we wouldn't have lots of important OS features. [0] http://en.wikipedia.org/wiki/Single_UNIX_Specification#2001:_POSIX:2001.2C_Single_UNIX_Specification_version_3 http://en.wikipedia.org/wiki/Single_UNIX_Specification#2001:...