A demo to show how to modify another process' memory

modify_mem.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <error.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int main(int argc , char ** argv){
  char buffer[50];
  char * despath = (char *)malloc( sizeof(char)*( sizeof(argv[1]) + sizeof("/proc//mem")) );
  sprintf(despath , "/proc/%s/mem",argv[1]);
  printf("despath %s\n" , despath);

  long long offset = 0x7ffd848e7040;
  printf("offset %p\n" , offset);
  int file = open(despath , O_RDWR  );
  if(file <= 0){
    printf("fopen error %s\n",strerror(errno));
    exit(0);
  }
  else
    printf("fopen succuessful\n");

  int err;
  printf("lseek %d\n" ,file);
  if(lseek(file , offset ,SEEK_SET) == -1){
    printf("fseek error %s \n" ,strerror(errno));
  }

  int lenth;
  if(( lenth = read(file , buffer , sizeof(buffer)) )> 0 )
    printf("buffer %s \n" , buffer);
  else
  {
    printf("lenth %d\n" , lenth);
  }
  lseek(file , offset ,SEEK_SET);
  write(file , "you must be changed  one more time\n" , 
      sizeof("you must be changed  one more time\n"));
  close(file);
  return 0;
}