08:58am ccbsd3:readfile/> g++ testfile.cpp
08:58am ccbsd3:readfile/> ./a.out 

Test file I/O --- by tsaiwn@csie.nctu.edu.tw

== call test1 to test printf with wrong %format ==
in test1 ..
kk=12345678  ??  12345678  ???   12345678
 Correct kk=12345678
================
    1    2    3    4    5    6    7    8    9
    2    4    6    8   10   12   14   16   18
    3    6    9   12   15   18   21   24   27
    4    8   12   16   20   24   28   32   36
    5   10   15   20   25   30   35   40   45
    6   12   18   24   30   36   42   48   54
    7   14   21   28   35   42   49   56   63
    8   16   24   32   40   48   56   64   72
    9   18   27   36   45   54   63   72   81
TEST.del created!
-rw-------  1 tsaiwn  faculty  22 Jan  3 12:05 TEST.del
Hey, you!
Hello world
ÿ
%  cat -n TEST.del
     1  Hey, you!
     2  Hello world

Bye bye!
08:58am ccbsd3:readfile/>


10:18am ccbsd3:readfile/> cat -n f7.c
     1	//f7.c -- by tsaiwn@csie.nctu.edu.tw
     2	#include <stdio.h>
     3	int x, k;
     4	long sum;
     5	int main( ) {
     6	   FILE* fp;
     7	   fp=freopen("in.txt", "rt", stdin);  // §ï±q in.txt Ū
     8	   if(fp==0) { perror("Open error."); exit(38); }
     9	   sum = k=0;
    10	   printf("x=? ");
    11	   scanf("%d", &x);
    12	   while( !feof(stdin) ) {
    13	      printf("Got %d\n", x);
    14	      ++k;  // count
    15	      sum += x;
    16	      printf("x=? ");
    17	      scanf("%d", &x);
    18	   }
    19	   printf("Total %d numbers. Sum=%d\n", k, sum);
    20	   return 0;
    21	}

10:18am ccbsd3:readfile/> gcc f7.c
10:18am ccbsd3:readfile/> ./a.out
Open error.: No such file or directory
10:18am ccbsd3:readfile/> vi in.txt
10:18am ccbsd3:readfile/> cat in.txt
12
23
33
50
88

10:18am ccbsd3:readfile/> ./a.out
x=? Got 12
x=? Got 23
x=? Got 33
x=? Got 50
x=? Got 88
x=? Total 5 numbers. Sum=206
10:18am ccbsd3:readfile/> exit