What does fread mean in C language?

fread is a library function in C language used to read data from a stream into a buffer. Its prototype is: size_t fread(void ptr, size_t size, size_t count, FILE stream), where: ptr points to the buffer, size is the size of each element, count is the number of elements to be read, and stream is the data to be read. of flow. fread returns the number of elements actually read, which is equal to count on success, otherwise it returns a smaller value.

The meaning of fread in C language

fread is a standard library function in C language, used to read from Read data from a stream (such as a file or pipe) into a buffer.

Detailed description:

The prototype of the fread function is:

<code class="c">size_t fread(void *ptr, size_t size, size_t count, FILE *stream);</code>

Among them:

• ptr: Pointer to the buffer used to store data read from the stream.
• size: The size (in bytes) of each element to be read.
• count: The number of elements to read.
• stream: The stream to read data from, usually a file pointer.

The fread function returns the actual number of elements read. If the read operation completes successfully, this will equal count. If an error is encountered or the end of file is reached, it will return a smaller value.

Usage:

The fread function can be used to read data from a variety of sources, including:

• files (using fopen Open)
• Pipe (created using pipe)
• Socket (created using socket)

When using the fread function, it is important to ensure that the buffer size is large enough to accommodate the data being read. If the buffer is too small, the fread function will return a truncated read result.

Example:

The following example shows how to use the fread function to read data from a file:

<code class="c">#include <stdio.h>

int main() {
    FILE *file = fopen("data.txt", "r");
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // 创建一个缓冲区
    char buffer[1024];

    // 从文件中读取数据到缓冲区
    size_t count = fread(buffer, sizeof(char), 1024, file);

    // 检查是否成功读取数据
    if (count != 1024) {
        perror("Error reading from file");
        fclose(file);
        return 1;
    }

    // 处理缓冲区中的数据

    fclose(file);
    return 0;
}</code>

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