C Programming/File Manipulation

When accessing files through C, the first necessity is to have a way to access the files. For C File I/O you need to use a FILE pointer, which will let the program keep track of the file being accessed. For Example:

FILE *fp;

To open a file you need to use the fopen function, which returns a FILE pointer. Once you've opened a file, you can use the FILE pointer to let the compiler perform input and output functions on the file.

FILE *fopen(const char *filename, const char *mode);

Here filename is string literal which you will use to name your file and mode can have one of the following values

w  - open for writing (file need not exist)
a  - open for appending (file need not exist)
r+ - open for reading and writing, start at beginning
w+ - open for reading and writing (overwrite file)
a+ - open for reading and writing (append if file exists)

File Write

//main.c
#include <stdio.h>

int main(void)
{
    FILE *fp;

    fp    = fopen("./test.txt", "w");
    fprintf(fp, "Hello text archive\n");
    //fclose(fp;);
    fclose(fp);

    return 0;
}

File Read

//main.c
#include <stdio.h>

int main(void)
{
    FILE *fp;
    char buffer[20];

    fp    = fopen("./test.txt", "r");
    fscanf(fp, "%s", buffer);
    //printf("Read Buffer: %s\n", %buffer);
    printf("Read Buffer: %s\n", buffer);
    //fclose(fp;);
    fclose(fp);
    return 0;
}

Binary IO

//for read binary data from file  
size_t fread(void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file);

//for write binary data into file     
size_t fwrite(const void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file);