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This article will explain in detail how to implement file operation in C language. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

What is a file?

The file on the disk is the file.

In programming, we generally talk about two kinds of files: program files and data files.

Program file

Includes source program files (suffix .c), destination files (windows environment suffix .obj), and executable programs (windows environment suffix .exe).

Data file

The content of the file is not necessarily the program, but the data read and written when the program is running, such as the file from which the program needs to read the data, or the file that outputs the content.

File name

The file name consists of three parts: file path, file name trunk, and file name suffix.

For example: C:\ code\ test.txt

File type

According to the organization of the data, the file type is divided into text file or binary file.

The data is stored in binary form in memory. If it is not converted and output to external memory, it is a binary file. If it is converted before external storage, the file stored in the form of ASCII characters is a text file.

How is a data stored in memory?

All characters are stored in ASCII form, and numerical data can be stored either in ASCII form or in binary form.

For example, if the integer 10000 is output to disk in ASCII form, it takes up 5 bytes (one byte for each character), while the output in binary form takes only 4 bytes.

File buffer

The ASNIC standard uses "buffered file system" to process data files.

The buffered file system means that the system automatically opens a "file buffer" in memory for each file being used in the program.

Transferring data from memory to disk will first be sent to the cache area in memory, and then sent to the disk when the cache area is full.

If you read the data from the disk to the computer, read the data from the disk file to the memory buffer, and then send the data from the buffer to the program data segment (program variables, etc.) one by one after the buffer is filled. The buffer size is determined according to the c compilation system

File pointer

Each used file opens a corresponding file information area in memory, which is used to store the relevant information of the file (such as the name of the file, the status of the file, the current location of the file, etc.). This information is stored in a structural variable. The structure type is systematically declared and is named FILE.

A pointer to a FILE is called a file pointer

Whenever a file is opened, the system automatically creates a variable of the FILE structure according to the condition of the file, and fills in the information in it. The user does not have to care about its details.

Opening and closing of files

File should be opened before reading and writing, and should be closed after use.

ANSIC stipulates that files are opened using fopen, and files are closed by fclose

FILE* fopen (const char* filename, const char* mode)

Parameter 1 is the file name, and parameter 2 is open mode

A successful opening returns a file pointer, while a failure returns a null pointer.

Int fclose (FILE* stream)

Return 0 for successful shutdown and EOF for failure

There are many ways to open a file, as shown in the figure

Input and output

After opening, you can input and output data, which can be operated with the following functions

Note: the following are sequential read and write functions

Specific use case

Example 1 (with running results)

Example 2

Example 3

After learning the file operation, you can modify the previous address book to the file version.

This is the end of the article on "how to operate files in C language". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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