Advanced Programming in the UNIX® Environment

ptg10805159

30 UNIX Standardization and Implementations Chapter 2

FreeBSD Linux Mac OS X Solaris

Header 8.0 3.2.0 10.6.8 10 Description

<fmtmsg.h> •• ••message display structures

<ftw.h> •• ••file tree walking (Section 4.22)

<libgen.h> •• ••pathname management functions

<ndbm.h> •••database operations

<search.h> •• ••search tables

<syslog.h> •• ••system error logging (Section 13.4)

<utmpx.h> •• •user accounting database

<sys/ipc.h> •• ••IPC (Section 15.6)

<sys/msg.h> •• ••XSI message queues (Section 15.7)

<sys/resource.h> •• ••resource operations (Section 7.11)

<sys/sem.h> •• ••XSI semaphores (Section 15.8)

<sys/shm.h> •• ••XSI shared memory (Section 15.9)

<sys/time.h> •• ••time types

<sys/uio.h> •• ••vector I/O operations (Section 14.6)

Figure 2.3 XSI option headers defined by the POSIX standard

After morethan twenty years of work, the standards arematureand stable. The

POSIX.1 standard is maintained by an open working group known as the Austin Group

(http://www.opengroup.org/austin). Toensurethat they arestill relevant, the

standards need to be either updated or reaffirmed every so often.

2.2.3 The Single UNIX Specification

The Single UNIX Specification, a superset of the POSIX.1 standard, specifies additional

interfaces that extend the functionality provided by the POSIX.1 specification. POSIX.1

is equivalent to the Base Specifications portion of the Single UNIX Specification.

TheX/Open System Interfaces(XSI)option in POSIX.1 describes optional interfaces

and defines which optional portions of POSIX.1 must be supported for an

implementation to be deemedXSI conforming.These include file synchronization,

thread stack address and size attributes, thread process-shared synchronization, and the

_XOPEN_UNIXsymbolic constant (marked ‘‘SUS mandatory’’ in Figure2.5). Only XSI-

conforming implementations can be called UNIX systems.

The Open Group owns the UNIX trademark and uses the Single UNIX Specification to define

the interfaces an implementation must support to call itself a UNIX system.Vendors must file

conformance statements, pass test suites to verify conformance, and license the right to use the

UNIX trademark.

FreeBSD Linux Mac OS X Solaris

Header 8.0 3.2.0 10.6.8 10 Description

<mqueue.h> •• •message queues

<spawn.h> •• ••real-time spawn interface

Figure 2.4 Optional headers defined by the POSIX standard