C POSIX library

The C POSIX library is a language-independent library (using C calling conventions) that adds functions specific to POSIX systems. POSIX (and SUS) specifies a number of routines that should be available over and above those in the C standard library proper. It was developed at the same time as the ANSI C standard and is closely related to C. Some effort was made to make the C and POSIX libraries compatible, but there are a few POSIX functions that were never introduced into ANSI C.

Facilities are often implemented alongside the C standard library functionality, with varying degrees of closeness. For example, glibc implements functions such as fork within libc.so, but before NPTL was merged into glibc it constituted a separate library with its own linker flag. Often, this POSIX-specified functionality will be regarded as part of the library; the C library proper may be identified as the ANSI or ISO C library.

C POSIX library header files

<cpio.h>	Magic numbers for the cpio archive format.
<dirent.h>	Allows the opening and listing of directories.
<fcntl.h>	File opening, locking and other operations.
<grp.h>	User group information and control.
<pwd.h>	passwd (user information) access and control.
<sys/ipc.h>	Inter-process communication (IPC).
<sys/msg.h>	POSIX message queues.
<sys/sem.h>	POSIX semaphores.
<sys/stat.h>	File information (stat et al).
<sys/time.h>	Time and date functions and structures.
<sys/types.h>	Various data types used elsewhere.
<sys/utsname.h>	uname and related structures.
<sys/wait.h>	Status of terminated child processes (see wait)
<tar.h>	Magic numbers for the tar archive format.
<termios.h>	Allows terminal I/O interfaces.
<unistd.h>	Various essential POSIX functions and constants.
<utime.h>	inode access and modification times.

References

• Lists headers in the POSIX library
• about termios.h
• Description of the posix library