[英]How can I fix the problem with gets() function in C?
There is a problem with gets
function. gets
function 存在问题。 The first gets
I write does not work but the ones comes next works properly.我
gets
的第一个不工作,但接下来的工作正常。
I put an extra gets()
function at the beginning, program just skips it and gets the string I want.我在开头放了一个额外的
gets()
function,程序只是跳过它并获取我想要的字符串。 But it is not safe and reliable.但它并不安全可靠。 So what is the problem with gets and how can I fix it?
那么gets有什么问题,我该如何解决呢?
if (choice == 1) {
printf("Please enter an English phrase with upper case: ");
gets(a);
gets(engphr);
for (i = 0; engphr[i] != '\0'; i++) {
As Eraklon mentions in their comment, the most likely cause is that you have a scanf
call before the gets
call, and the trailing newline from the previous input is getting consumed by gets
before you have a chance to enter anything else.正如 Eraklon 在他们的评论中提到的那样,最可能的原因是您在调用
gets
之前有一个scanf
调用,并且gets
您有机会输入其他任何内容之前,来自先前输入的尾随换行符已被 get 消耗。
You should never use gets
anyway - it was removed from the standard library in the 2011 version of the language.无论如何,您都不应该使用
gets
- 它已从 2011 版语言的标准库中删除。 It is inherently unsafe to use, and will introduce a security hole in your code.使用它本质上是不安全的,并且会在您的代码中引入安全漏洞。 Use
fgets
instead.请改用
fgets
。 Its behavior is slightly different (it will save the trailing newline to the input buffer if there's room, where gets
discarded it), but it's much safer:它的行为略有不同(如果有空间,它会将尾随换行符保存到输入缓冲区,在哪里
gets
丢弃),但它更安全:
if ( fgets( engphr, sizeof engphr, stdin ) ) // assumes engphr is declared as an array, not a pointer
{
// process engphr
}
Having said that, you really shouldn't mix calls to scanf
and fgets
, again because scanf
will leave trailing newlines in the input stream from previous inputs, and fgets
will immediately return after seeing that newline.话虽如此,您真的不应该混合对
scanf
和fgets
的调用,因为scanf
会在输入 ZF7B44CFFAFD5C52223D5498196C8A2E7BZ 中留下来自先前输入的尾随换行符,并且fgets
将在看到该换行符后立即返回。 Either read all input using fgets
and use sscanf
to read specific items from the input buffer, or read all input with scanf
.使用
fgets
读取所有输入并使用sscanf
从输入缓冲区中读取特定项目,或者使用scanf
读取所有输入。
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