将recvfrom（）结果接收到的缓冲区与文本文件进行比较

Question

I have a Buffer received as a result of recvfrom(). lets say,

char receiveBuffer[12] = "NewClient 5";

I want have a text file which looks like this:

NewClient 1 192.168.1.1 8881
NewClient 2 192.168.1.1 8882
NewClient 3 192.168.1.1 8883
NewClient 4 192.168.1.1 8884
NewClient 5 192.168.1.1 8885
NewClient 6 192.168.1.1 8886
NewClient 7 192.168.1.1 8887
NewClient 8 192.168.1.1 8888
and so on..

Lets suppose receiveBuffer has "NewClient 5" in it. Now what I want is that compare my receiveBuffer with contents of the file. When receiveBuffer matches contents of the file eg in this case Line#5 has same starting contents as in my receiveBuffer, then I want to copy the corresponding number "192.168.1.1 8885" to a sendBuffer.

How can this be done? How would I compare only starting 11 bytes including a space of text file with my receiveBuffer? :(

I can do it by reading the file character by character by using getc() but I don't know how to compare a fixed number of bytes from file and if the comparison is false then jump to next line ignoring all other remaining bytes in that line?

Any help is welcome. Thanks in advance :)

Answer 1

char * filename; // needs to be defined somewhere
FILE* fp = fopen(filename, "r");

char line[1024]; // assuming 1024 is the longest a line can be
while (fgets(line, sizeof(line), fp)) {
    if (!memcmp(line, receiveBuffer, strlen(receiveBuffer))) {
        // found the line

        char * remainder_of_line = line + strlen(receiveBuffer);
        // do whatever you want with the rest of the line found at remainder_of_line


        // optionally if you are only interested in the first matching line
        break;
    }
}

fclose(fp);