我写了这个C程序：
#include <stdio.h>
main()
{
int numspaces, numtabs, numnl, c;
while ((c = getchar()) != EOF){
if (c == ' ') ++numspaces;
if (c == '\t') ++numtabs;
if (c == '\n') ++ numnl;
}
printf("Spaces:\t\t%d\nTabs:\t\t%d\nNew lines:\t\t%d\n", numspaces, numtabs, numnl);
}
I think this while loop must finish when I press Ctrl+D and "return". It does if Ctrl+D is the first thing I type in a line. But if I start a line with other character (letter, space, tab) and then Ctrl+D and then "return" - the loop continues.
我在 Mac OS X 终端中测试了这个，我看到它回显^D并且它仍然继续循环。我在这里缺少什么？
CTRL-D or more precisely the character set to the VEOF entry of the c_cc field of a termios control structure (stty is the easiest way to query and modify those settings from the command line) is to be interpreted as (quote from the Single Unix Specification V4):
输入上的特殊字符，如果设置了 ICANON 标志，则可以识别该字符。当接收到时，所有等待读取的字节立即传递给进程，而不等待 ，并且 EOF 被丢弃。因此，如果没有字节等待（即 EOF 发生在行的开头），则 read() 应返回字节计数为零，表示文件结束指示。如果设置了 ICANON，则处理时 EOF 字符将被丢弃。
Thus to send a EOF indication from a terminal you hit CTRL-D once when there is no bytes waiting to be returned (typically at the start of a line), and twice when there are some.
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