How does the Single UNIX Specification compare to the Linux Standard Base?
The Single UNIX Specification specifies application programming interfaces (APIs) at the source level, and is about application source code portability. Its neither a code implementation nor an operating system, but a stable definition of a programming interface that those systems supporting the specification guarantee to provide to the application programmer. Efforts such as the Linux Standard Base, and similarly the iBCS2 for x86 implementations of System V, are about binary portability and define a specific binary implementation of an interface to operating system services. The LSB draws on the Single UNIX Specification for many of its interfaces although does not formally defer to it preferring to document any differences where they exist, such as where certain aspects of Linux cannot currently conform to the industry standards. Some interfaces are not included in the LSB, since they are outside the remit of a binary runtime environment, typically these are development interfaces o
