linux 如何禁止修改文件内容 用C语言代码实现

要用 C 语言代码实现禁止修改 Linux 文件内容的功能，可以使用以下代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    // Set the file path and content that you want to protect
    char* file_path = "/etc/hosts";
    char* file_content = "127.0.0.1   localhost\n127.0.1.1   myhostname\n";

    // Open the file in read-only mode
    FILE* fp = fopen(file_path, "r");
    if (fp == NULL) {
        printf("Failed to open the file!\n");
        return 1;
    }

    // Read the file content into a buffer
    fseek(fp, 0L, SEEK_END);
    long file_size = ftell(fp);
    rewind(fp);
    char* buffer = (char*) malloc(file_size + 1);
    fread(buffer, file_size, 1, fp);
    buffer[file_size] = '\0';

    // Compare the file content with the protected content
    if (strcmp(buffer, file_content) != 0) {
        printf("The file has been modified! Restoring the original content...\n");

        // Open the file in write mode and overwrite the content with the protected content
        fp = fopen(file_path, "w");
        if (fp == NULL) {
            printf("Failed to open the file in write mode!\n");
            return 1;
        }
        fputs(file_content, fp);
        fclose(fp);

        printf("The file has been restored to its original content!\n");
    } else {
        printf("The file has not been modified.\n");
    }

    // Free the buffer and close the file
    free(buffer);
    fclose(fp);

    return 0;
}

这段代码首先指定要保护的文件路径和内容，然后打开该文件并读取其内容到一个缓冲区中。接下来，将缓冲区的内容与要保护的内容进行比较，如果不同，则将文件内容恢复为要保护的内容。最后，释放缓冲区并关闭文件。

需要注意的是，这段代码只能保护指定的文件，如果要保护多个文件，需要对代码进行相应的修改。此外，该代码需要以 root 用户身份运行，否则可能无法读写受保护的文件。