把一个字符退回到输入流中

[c]代码库

#include <stdio.h> 
#include <ctype.h> 

int main( void ) 
{ 
   int i=0; 
   char ch; 

   puts("Input an integer followed by a char:"); 

   /* read chars until non digit or EOF */ 
   while((ch = getchar()) != EOF && isdigit(ch)) 
      i = 10 * i + ch - 48; /* convert ASCII into int value */ 

   /* if non digit char was read, push it back into input buffer */ 
   if (ch != EOF) 
      ungetc(ch, stdin); 

   printf("i = %d, next char in buffer = %c\n", i, getchar()); 
   return 0; 
}