The C POSIX library is a specification of a C standard library for POSIX systems. It was developed at the same time as the ANSI C standard. Some effort was made to make POSIX compatible with standard C; POSIX includes additional functions to those introduced in standard C. On the other hand, the 5 headers that were added to the C standard library with C11, were not likewise included in subsequent revisions of POSIX.
| Header file | Description | First released | C Standard | |
|---|---|---|---|---|
| Issue 5 | ||||
| Functions for manipulating numeric IP addresses (part of Berkeley sockets) | Issue 6 | |||
| Verify assumptions | Issue 1 | ANSI (89) | ||
| Issue 6 | C99 | |||
| Magic numbers for the cpio archive format | Issue 3 | |||
| Character types | Issue 1 | ANSI (89) | ||
| Issue 2 | ||||
| Issue 5 | ||||
| Retrieving Error Number | Issue 1 | ANSI (89) | ||
| File opening, locking and other operations | Issue 1 | |||
| Issue 6 | C99 | |||
| Issue 4 | ANSI (89) | |||
| Message display structures | Issue 4 | |||
| Filename matching | Issue 4 | |||
| File tree traversal | Issue 1 | |||
| Pathname "globbing" (pattern-matching) | Issue 4 | |||
| User group information and control | Issue 1 | |||
| Codeset conversion facility | Issue 4 | |||
| Issue 5 | C99 | |||
| Issue 5 | NA1 (95) | |||
| Issue 2 | ||||
| Pathname manipulation | Issue 4 | |||
| Issue 1 | ANSI (89) | |||
| Issue 3 | ANSI (89) | |||
| Issue 1 | ANSI (89) | |||
| String formatting of monetary units | Issue 4 | |||
| Issue 5 | ||||
| NDBM database operations | Issue 4 | |||
| Listing of local network interfaces | Issue 6 | |||
| Translating protocol and host names into numeric addresses (part of Berkeley sockets) | Issue 6 | |||
| Defines Internet protocol and address family (part of Berkeley sockets) | Issue 6 | |||
| Additional TCP control options (part of Berkeley sockets) | Issue 6 | |||
| Localization message catalog functions | Issue 2 | |||
| Issue 4 | ||||
| Issue 5 | ||||
| passwd (user information) access and control | Issue 1 | |||
| Regular expression matching | Issue 4 | |||
| Execution scheduling | Issue 5 | |||
| Search tables | Issue 1 | |||
| Issue 5 | ||||
| Stack environment declarations | Issue 1 | ANSI (89) | ||
| Issue 1 | ANSI (89) | |||
| Issue 6 | ||||
| Handle Variable Argument List | Issue 4 | ANSI (89) | ||
| Issue 6 | C99 | |||
| Issue 4 | ANSI (89) | |||
| Issue 6 | C99 | |||
| Issue 1 | ANSI (89) | |||
| Issue 3 | ANSI (89) | |||
| Issue 1 | ANSI (89) | |||
| Case-insensitive string comparisons | Issue 4 | |||
| Issue 4 | ||||
| Inter-process communication (IPC) | Issue 2 | |||
| Issue 4 | ||||
| POSIX message queues | Issue 2 | |||
| Resource usage, priorities, and limiting | Issue 4 | |||
| Issue 6 | ||||
| Issue 2 | ||||
| Issue 2 | ||||
| Main Berkeley sockets header | Issue 6 | |||
| File information (stat et al.) | Issue 1 | |||
| File System information | Issue 4 | |||
| Time and date functions and structures | Issue 4 | |||
| File access and modification times | Issue 1 | |||
| Various data types used elsewhere | Issue 1 | |||
| Vectored I/O operations | Issue 4 | |||
| Unix domain sockets | Issue 6 | |||
| Issue 1 | ||||
| Status of terminated child processes (see wait) | Issue 3 | |||
| Issue 4 | ||||
| Magic numbers for the tar archive format | Issue 3 | |||
| Allows terminal I/O interfaces | Issue 3 | |||
| Issue 6 | C99 | |||
| Issue 1 | ANSI (89) | |||
| Tracing of runtime behavior (DEPRECATED) | Issue 6 | |||
| Resource limiting (DEPRECATED in favor of | Issue 1 | |||
| Various essential POSIX functions and constants | Issue 1 | |||
| inode access and modification times | Issue 3 | |||
| User accounting database functions | Issue 4 | |||
| Issue 4 | NA1 (95) | |||
| Issue 5 | NA1 (95) | |||
| Word-expansion like the shell would perform | Issue 4 |