Kernighan 和 Ritchie 问题 1-17 的 Printf 问题
在下面的代码中（Kernighan 和 Ritchie 编写的《C 编程语言》中的问题 1-17）为什么不打印最长的行（在底部）？
#include <stdio.h>
#define MAXLINE 1000
#define LONGLINE 10
int getLineLength(char line[], int maxline){
int i, c;
for(i = 0; i< maxline-1 && (c = getchar() != EOF) && c != '\n'; i++)
line[i] = c;
if(c == '\n') {
line[i] = c;
i++;
}
line[i] = '\0';
return i;
}
main() {
int len;
char line[MAXLINE];
while((len = getLineLength(line, MAXLINE)) > 0)
if(len > LONGLINE)
printf("The line was over the maxlength\n\t %s", line);
return 0;
}
In the code below (for problem 1-17 in "The C Programming Language", by Kernighan and Ritchie) why doesn't it print the longest line (at the bottom)?
#include <stdio.h>
#define MAXLINE 1000
#define LONGLINE 10
int getLineLength(char line[], int maxline){
int i, c;
for(i = 0; i< maxline-1 && (c = getchar() != EOF) && c != '\n'; i++)
line[i] = c;
if(c == '\n') {
line[i] = c;
i++;
}
line[i] = '\0';
return i;
}
main() {
int len;
char line[MAXLINE];
while((len = getLineLength(line, MAXLINE)) > 0)
if(len > LONGLINE)
printf("The line was over the maxlength\n\t %s", line);
return 0;
}
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评论（3）
在您的代码中：
这将被评估为
(c = (getchar() != EOF))，给出错误的结果。你需要的是：In your code:
This will be evaluated as
(c = (getchar() != EOF)), giving the wrong result. What you need is:该程序从标准输入读取数据，并打印长度超过 10 个字符的长消息。行以“\n”（换行符、ENTER）结束。如果您输入文件（例如通过管道），则输入以 EOF 结尾；如果您手动输入字符，则输入以 CTRL-C 结尾。
This program reads from standard input, and prints that long message for lines longer 10 than characters. Lines end with '\n' (newline, ENTER). Input ends with EOF, if you feed a file, e.g. through a pipe, or CTRL-C, if you enter characters manually.
我很惊讶这竟然有效。
(c = getchar() != EOF)从一开始就是完全错误的。line[i] = c;出现两次。我认为在边缘情况下它很容易受到缓冲区溢出的影响。编辑：我看不到更多的早期答案说你似乎在 for 循环中缺少大括号。
I'm surprised this works at all.
(c = getchar() != EOF)is completely wrong for a start.line[i] = c;appears twice. And I think it's vulnerable to a buffer overflow in an edge case.EDIT: An earlier answer that I can't see any more said that you seem to have your braces missing from the for loop.