void redirect(int argc, char *argv[])
{
   int flag;

   if (strcmp(argv[0], ">") == 0)
       flag = 1;
   else if (strcmp(argv[0], "<") == 0)
       flag = 2;
   else if (strcmp(argv[0], ">>") == 0)
       flag = 3;
   else
       printf("Something Wrong,Please Check!\n");

   switch (flag)  {

      case 1:
          freopen("out.txt","w",stdout);
          printf("This sentence is redirected to a file\n");
         // fclose(stdout);

      case 2:
          freopen("in","r",stdin);
          printf("This sentence is redirected to a file\n");
         // fclose(stdin);

      case 3:
          freopen("out.txt","a+",stdout);
          printf("This sentence is redirected to a file\n");
         // fclose(stdout);
      default:
          wait(5);
      }
}

void redirect1(int argc, char *argv[])
{
   char *str;
   str = argv[2];
       printf("This goes to the file %s\n",(char *)str);
       freopen((char *)str,"w",stdout);
          /* write the context into file "str" */
          /* ex: "ls > out" */
}

fprintf(stderr,"This is a message\n");

int redirect1(int argc, char *argv[])
{
   char *str;
   str = argv[2];
       printf("This goes to the file %s\n",(char *)str);
       freopen((char *)str,"w",stdout);
          /* write the context into file "str" */
          /* ex: "ls > out" */
}

int main(void)
{
...
if (strcmp(argv[1],">")==0)
                         { ret = redirect1(argc, argv);
                           printf("ret = %d\n",ret);}//never print//no print
...
}

if(freopen(str,"w",stdout)==NULL)
{
  fprintf(stderr,"Couldn't freopen\n");
  return(0);
}
else
  fprintf(stderr,"freopened to %s\n",str);

return(1);