Information that is needed by several different files or functions is collected into a header file. A header file contains C-language definitions and structures. Centralizing information into a header file facilitates the creation and update of programs. Because #include statements are used to insert header files into a C-language program, header files are often referred to as include files.
Header files define the following functions:
By convention, the names of header files end with .h (dot h). The .h suffix is used by header files that are provided with the operating system; however, the suffix is not required for user-generated header files.
Additional header files are provided with the operating system. Most of these can be found in either the /usr/include directory or the /usr/include/sys directory. Use the pg command to view the contents of a header file.
More information about the following header files is provided in this documentation:
| a.out.h | Defines the structure of the standard a.out file. |
| acct.h | Describes the format of the records in the system accounting files. |
| ar.h | Describes the format of an archive file. |
| audit.h | Defines values used by the auditing system as well as the structure of a bin. |
| core.h | Describes the structures created as a result of a core dump. |
| ct_ffdc.h | Provides data types, definitions, and interface prototypes for the First Failure Data Capture (FFDC) C language library interfaces. |
| dirent.h | Describes the format of a file system-independent directory entry. |
| eucioctl.h | Defines ioctl operations and data types for handling EUC code sets. |
| fcntl.h | Defines values for the fcntl and open subroutines. |
| filsys.h | Contains the format of a file system logical volume. |
| flock.h | Defines the file control options. |
| fullstat.h | Describes the data structure returned by the fullstat and ffullstat subroutines. |
| iconv.h | Defines types, macros, and subroutines for character code set conversion. |
| ipc.h | Defines structures used by the subroutines that perform interprocess communications operations. |
| ldr.h | Describes the ld_info data type and loader entry points. |
| libperfstst.h | Describes the structures and constants used by the libperfstat API subroutines. |
| limits.h | Defines implementation limits identified by the IEEE POSIX 1003 standard. |
| math.h | Defines math subroutines and constants |
| mode.h | Defines the interpretation of a file mode. |
| msg.h | Defines structures used by the subroutines that perform message queueing operations. |
| mtio.h | Defines the magnetic tape user include file. |
| param.h | Defines certain hardware-dependent parameters. |
| poll.h | Defines the pollfd structure used by the poll subroutine. |
| sem.h | Defines the structures that are used by subroutines that perform semaphore operations. |
| sgtty.h | Defines structures used by the Berkeley terminal interface. |
| shm.h | Defines structures used by the subroutines that perform shared memory operations. |
| spc.h | Defines external interfaces provided by the System Resource Controller (SRC) subroutines. |
| srcobj.h | Defines structures used by the System Resource Controller (SRC) subsystem. |
| stat.h | Describes the data structure returned by the status subroutines. |
| statfs.h | Describes the structure of the statistics returned by the status subroutines. |
| statvfs.h | Describes the structure of the statistics that are returned by the statvfs subroutines and fsatvfs subroutines. |
| systemcfg.h | Defines the _system_configuration structure. |
| tar.h | Defines flags used in the tar archive header. |
| termio.h | Defines structures used by the terminal interface for compatibility of Version 2 of the operating system. |
| termios.h | Defines structures used by the POSIX terminal interface. |
| termiox.h | Defines the structure of the termiox file, which provides the extended terminal interface. |
| trace.h | Defines implementation trace identified by IEEE POSIX 1003. |
| types.h | Defines primitive system data types. |
| unistd.h | Defines POSIX implementation characteristics. |
| utmp.h | Defines the format of certain user and accounting information files. |
| values.h | Defines hardware-dependent values. |
| vmount.h | Describes the structure of a mounted file system. |
| x25sdefs.h | Contains the structures used by the X.25 application programming interface. |
The pg command.
File Formats Overview defines and describes file formats in general and lists file formats discussed in this documentation.
Special Files Overview defines and describes special files in general and lists special files discussed in this documentation.