CODEWITHSUNDEEP
chttpweb
Sarius
Sarius

Reputation: 145

Reading content from a file and storing it to String in C

I've written a simple http server in C and am now trying to implement HTML files. For this I need send a response, containing the content of the HTML file. How do I do that best? Do I read the file line by line, and if so how do I store them in a single string? Thanks already!

Upvotes: 0

Views: 935

Answers (1)

Jerry Jeremiah
Jerry Jeremiah

Reputation: 9643

Here is an example of reading a text file by chunks which, if the file is big, would be faster than reading the file line by line.

As @tadman said in his comment, text files aren't generally big so reading them in chunks doesn't make any real difference in speed but web servers serve other files too - like perhaps photos or movies (which are big). So if you are only going to read text files then reading line by line might be simpler (you could use fgets instead of fread) but if you are going to read other kinds of files then reading all of them in chunks means you can do it the same way for all of them.

However, as @chux said in his comment, there is another difference between reading text files and binary files. The difference is that text files are opened in text mode: fopen(filename,"r"); and binary files must be opened in binary mode: fopen(filename,"rb"); A web server could probably open all files in binary mode because web browsers ignore whitespace anyway but other kinds of programs need to know what the line endings will be so it can make a difference.

https://onlinegdb.com/HkM---r2X

#include <stdio.h>

int main()
{
    // we will make the buffer 200 bytes in size
    // this is big enough for the whole file
    // in reality you would probably stat the file
    // to find it's size and then malloc the memory
    // or you could read the file twice:
    // - first time counting the bytes
    // - second time reading the bytes
    char buffer[200]="", *current=buffer;
    // we will read 20 bytes at a time to show that the loop works
    // in reality you would pick something approaching the page size
    // perhaps 4096?  Benchmarking might help choose a good size
    int bytes, chunk=20, size=sizeof(buffer)/sizeof(char);
    // open the text file in text mode
    // if it was a binary file you would need "rb" instead of "r"
    FILE *file=fopen("test.html","r");
    if(file)
    {
        // loop through reading the bytes
        do {
            bytes=fread(current,sizeof(char),chunk,file);
            current+=bytes;
        } while (bytes==chunk);
        // close the file
        fclose(file);
        // terminate the buffer so that string function will work
        *current='\0';
        // print the buffer
        printf("%s",buffer);
    }
    return 0;
}

Upvotes: 1

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