使用fread（）读取结构

Question

i am trying to use fread to enter data to this structure, i have defined this structure as an header like this

    #ifndef__HEADER_H__
    #define__HEADER_H__
    struct input_par
    {
        char key[5];
        char key_node[5];
        char src_ip[15];
        char dst_ip[15];
        char src_port[5];
        char dst_port[5];
    };

    #endif

in my main function, in file input_data i have stored this data

       @822!822!172.28.6.137!172.28.6.110!5000!6000| 

for me @ means start of the data and | means end of valid data here i want to enter 822 to key, 822 to key_node, 172.28.6.137 to src_ip and so on 6000 to dst_port, i am not able to do this for testing purpose i am just entering only 822 to key. I am using fread for the first time please help

    #include"file_header"
    #include <stdio.h>
    main()
    {
        int i;
        struct input_par input_par;
        FILE *fp;
        fopen("input_data","r");
        if(*fp == "@")
        {
            while(*fp!= "!")
            {
                for(i=0;i<5;i++)
                {
                    fread(&input_par.key, sizeof(input_par),1,fp);
                    printf("%d\n",input_par.key);
                }

            }
        }
        fclose(fp);
    }

Answer 1

Well, you have some errors in your code. As @unaperson pointed out, that is not the use of FILE, and definitely you should learn about it .

If you are going to read each char in the file, and interpret @ as a delimiter, you can use fgetc instead of fread, which is used for reading big chunks. Be aware that fgetc returns an int, in order to be able to check the end-of-file error condition (you cannot read anymore).

You can read each field until the next delimiter, and store it in the appropriate field of your struct.