What is the h file in linux

In Linux, the h file is a header file in the system. It is generally used to store some reused code, such as function declarations, variable declarations, constant declarations, macro definitions, etc.; the header file is a After editing the text file with a text editor, save it with the extension ".h".

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

What is the h file in Linux

The header file is a text file. After writing the code using a text editor, just save it with the extension .h. Header files generally contain some reused code, such as function declarations, variable declarations, constant definitions, macro definitions, etc.

There are a total of 32 .h header files in the header file directory. Among them, there are 13 in the main directory, 4 in the asm subdirectory, 10 in the Linux subdirectory, and 5 in the sys subdirectory.

• : a.out header file, which defines the a.out execution file format and some macros.

• : Constant symbol header file, currently only defines the flag bits of the i_mode field in the i node.

• : Character type header file, which defines some macros related to character type judgment and conversion.

• : Error number header file, containing various error numbers in the system. (Introduced by Linus from minix).

• : File control header file, used for the definition of operation control constant symbols for files and their descriptors.

• : Signal header file, defining signal symbol constants, signal structures and signal operation function prototypes.

• : Standard parameter header file, which defines the variable parameter list in the form of macros. It mainly explains one type (va_list) and three macros (va_start, va_arg and va_end), which are used for vsprintf, vprintf and vfprintf functions.

• : Standard definition header file, which defines NULL, offsetof(TYPE, MEMBER).

• : String header file, which mainly defines some embedded functions related to string operations.

• : Terminal input and output function header file, mainly defines the terminal interface that controls the asynchronous communication port.

• : Time type header file, which mainly defines the tm structure and some time-related function prototypes.

• : Linux standard header file, which defines various symbolic constants and types, and declares various functions. For example, if __LIBRARY__ is defined, it also includes the system call number and inline assembly _syscall0(), etc.

• : User time header file, which defines the access and modification time structure and utime() prototype.

Architecture-related header file subdirectory include/asm

These header files mainly define some data structures, macro functions and variables that are closely related to the CPU architecture. 4 files in total.

• : I/O header file, which defines functions for operating I/O ports in the form of macro embedded assembler.

• : Memory copy header file, containing memcpy() embedded assembly macro function.

• : Segment operation header file, which defines embedded assembly functions related to segment register operations.

• : System header file, which defines embedded assembly macros for setting or modifying descriptors/interrupt gates, etc.

Linux kernel-specific header file subdirectory include/linux

• : kernel Configure the header file to define keyboard language and hard disk type (HD_TYPE) options.

• : Floppy drive header file, containing some definitions of floppy disk controller parameters.

• : File system header file, defining the file table structure (file, buffer_head, m_inode, etc.).

• : Hard disk parameter header file, which defines access to hard disk register ports, status codes, partition tables and other information.

• : The head header file defines the simple structure of the segment descriptor and several selector constants.

• : Kernel header file, containing prototype definitions of some commonly used kernel functions.

• : Memory management header file, containing page size definition and some page release function prototypes.

• : Scheduler header file, which defines the task structure task_struct and the data of initial task 0,

As well as some embedded assembly function macro statements related to descriptor parameter setting and acquisition.

• : System call header file, containing 72 system call C function handlers, starting with "sys_".

• : tty header file defines parameters and constants related to tty_io and serial communication.

System-specific data structure subdirectory include/sys

• : File status header file, containing file or file system status Structure stat{} and constants.

• : Defines the running time structure tms and times() function prototype in the process.

• : Type header file, which defines basic system data types.

• : System name structure header file.

• : Waiting call header file, defining system calls wait() and waitpid() and related constant symbols.

Commonly used header files in Linux

Header files defined by POSIX standards

• Directory entry

• File control

• File name matching type

• Pathname pattern matching type

• ## Group file

• Network database operation

• Password file

## Regular expression Formula
TAR archive value
Terminal I/O
Symbolic constant
File time
Character extension type
INTERNET definition

• ## Socket Local interface

• INTERNET address family

• ## Transmission Control Protocol Definition

• Memory management statement

• Select function

• Socket interface

• File status

• Process time

• Basic system data type

• ##< sys/un.h> UNIX domain socket definition

## System name
Process control
##XSI extension header file defined by POSIX

g`" Dynamic link

Message display structure

• ## File tree roaming

• Code set conversion usage program

• Language information constant

• Pattern matching function definition

• ## Currency type

## Database operation
Message category

• ## Polling function

• Search table

• ## String operation

• ## System error log record

• User context

## User limit
User Account Database
IPC (Named Pipe)
Message queue
Resource operation

• ##< sys/sem.h> Semaphore

• Shared storage

• ## File system information

• Time type

• Appended date and time Definition

• Vector I/O operation

• ##OPSIX-defined optional header file

• ## Asynchronous I/O

• ## Message queue

• Thread

## Execution scheduling

Semaphore

• Real-time spawn interface

• ## XSI STREAMS interface

• Event tracking

• Recommended learning:

  Linux video tutorial

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