Unix System Programming (1092)-exer1

exercise 1: a simple C program

• Write a C program which reads strings from stdin and if a string is consisted of digits, it is treated as a number. Sum all the numbers and write sum to stdout.
• The reading is terminated by end of file, that is, a ctrl-D.
• The length of each string does not exceed 16.
• You may assume the numbers and the sum can be handled with int.
• For converting a string to a number, you may consult strtol().
• For example:

  $ gcc ex1-sum-stdin.c 
  $ ./a.out 
  I have 1000
  You have 200
  I give you 50
  Now You have 250.   <---- ctrl-D pressed
  1250                <---- only 1000, 200, 50 are summed
  $ ./a.out 
  100 + 23 = 123
  $100 - 23 = 77.     <---- ctrl-D pressed
  269                 <---- 100, 23, 123, 23 are summed

  My program：
  https://ideone.com/V3fc8b
  https://ideone.com/hFVjyY