Linux File Read and Write - C++ [Updated] -

i supposed create program reads source.txt's first 100 characters, write them in destination1.txt, , replace "2" "s" , write them destination2.txt. below code

#include <sys/types.h> #include <unistd.h> #include <sys/stat.h> #include <fcntl.h> #include <cstdio> #include <iostream>  using namespace std;  int main(int argc, const char* argv[]){     argv[0] = "source.txt";     argv[1] = "destination1.txt";     argv[2] = "destination2.txt";     int count=100;     char buff[125];     int fid1 = open(argv[0],o_rdwr);      read(fid1,buff,count);     close(fid1);      int fid2 = open(argv[1],o_rdwr);     write(fid2,buff,count);     close(fid2);      //how change characters?     return 0; } 

thanks guys able copying. how perform character replacement? if it's fstream know how loop. i'm supposed use linux system calls.

define array out_buf , copy buff out_buf character character, replacing 2's s.

... read(fid1,buff,count); close(fid1);  char out_buf [125]; int i; (i = 0; < sizeof (buf); i++) {     if (buff [i] == '2')        out_buf [i] = 's'     else        out_buf [i] = buff [i] } int fid2 = open(argv[1],o_rdwr); write(fid2, out_buf,count); close(fid2);  return 0;