How can I get a file"s size in C?

📁 How to Get a File's Size in C 🤔

So, you're coding in C and wondering how to find the size of a file? Don't worry, we've got you covered! Knowing the size of a file is essential, especially if you want to allocate memory dynamically using malloc() or perform any file operations.

🧐 The Common Issue

Let's dive into the problem you encountered. You have a file you opened in your C application and you want to determine its size. This is especially useful if you plan to load the file content into a string, allocated using malloc(). After all, just blindly allocating memory with something like malloc(10000*sizeof(char)); is simply not the way to go.

💡 The Easy Solutions

Thankfully, there are a couple of easy ways to get the size of a file in C. Here are our top two recommendations:

1. Using fseek() and ftell()

#include <stdio.h>

long getFileSize(FILE *file) {
    long size;

    fseek(file, 0, SEEK_END);  // Move the file pointer to the end of the file
    size = ftell(file);  // Get the current position of the file pointer (which is the file size)
    rewind(file);  // Reset the file pointer to the beginning of the file

    return size;
}

int main() {
    FILE *file = fopen("your_file.txt", "r");
    if (file != NULL) {
        long size = getFileSize(file);
        printf("The file size is %ld bytes.\n", size);
        fclose(file);
    }

    return 0;
}

Here, we define a function getFileSize() that takes a FILE* as an argument and returns the size of the file. We achieve this by moving the file pointer to the end of the file using fseek() with the SEEK_END constant. Then, we retrieve the current position of the file pointer using ftell(), which gives us the file size. Finally, we rewind the file pointer back to the beginning of the file using rewind() to avoid any unexpected behavior in subsequent file operations.

2. Using stat()

#include <stdio.h>
#include <sys/stat.h>

long getFileSize(const char *filename) {
    struct stat st;

    if (stat(filename, &st) == 0)
        return st.st_size;

    return -1;  // Error occurred
}

int main() {
    const char *filename = "your_file.txt";
    long size = getFileSize(filename);

    if (size != -1)
        printf("The file size is %ld bytes.\n", size);
    else
        printf("Error occurred while getting the file size.\n");

    return 0;
}

Using stat(), we obtain and store file information in a struct stat. The st_size field of the structure contains the file's size. Simple, right?

🔥 The Compelling Call-to-Action

With these two easy-to-implement solutions, finding the size of a file in your C application shouldn't be a daunting task anymore. Choose the approach that suits your needs best, and feel free to experiment and explore further possibilities.

Have you encountered any other file-related issues or have more C-related questions? Leave a comment below and let's continue the conversation! Happy coding! 😄👨‍💻💬