为什么此C程序在输出中输出奇怪的字符? [英] Why does this C program print weird characters in output?
问题描述
我有以下程序:
#include <stdio.h>
int main()
{
int ch;
while( ch = getchar() != '\n') {
printf("Read %c\n",ch);
}
return 0;
}
无论我输入什么,我都会得到:
No matter what I enter I get:
Read
为什么会这样?我看到的是什么奇怪的字符?
Why is this happening and what is that weird char that I see?
Stackoverflow没有打印出奇怪的字符.您可以在这里看到它: http://ideone.com/EfZHr
Stackoverflow is not printing the weird char. You can see it here: http://ideone.com/EfZHr
推荐答案
您需要将括号放置为:
while( (ch = getchar()) != '\n')
优先级 大于 与:
读取char的 将其与换行符进行比较,然后将比较结果分配给ch.现在比较的结果是 which reads a char compares it with newline and then assigns the result of comparison to ch. Now the result of comparison is 您看到的奇怪字符是 控制字符 的值为 The weird char you're seeing is the control char with value 您可以通过将程序输出管道传输到八进制转储(od)来确认: You can confirm it by piping your program output to octal dump (od) : 与 GCC when used with 这篇关于为什么此C程序在输出中输出奇怪的字符?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!=
while( ch = getchar() != '\n')
while( ch = (getchar() != '\n') )
0
(输入换行符时)或1
(输入其他任何内容时)0
(when newline is entered) or 1
(when anything else is entered)1
,没有ASCII 1的可打印符号,因此我猜想它是在其中打印出值为0001
的奇怪字符的shell. 1
, there is no printable symbol for ASCII 1, so I guess its the shell that prints the weird char with value 0001
in it. $ echo 'a' | ./a.out | od -bc # user entered 'a'
0000000 122 145 141 144 040 001 012
R e a d 001 \n
here you go ----------------^
$ echo '\n' | ./a.out | od -bc # user entered '\n'
0000000
-Wall
一起使用时的GCC警告您:-Wall
warns you as:warning: suggest parentheses around assignment used as truth value