C语言 如何将char/int添加到C中的char数组？
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How to add a char/int to an char array in C?
提问by missjohanna
How can I add '.' to the char Array := "Hello World" in C, so I get a char Array: "Hello World." The Question seems simple but I'm struggling.
我怎样才能添加“。” 到 C 中的 char Array := "Hello World"，所以我得到一个 char Array："Hello World。" 这个问题看起来很简单，但我很挣扎。
Tried the following:
尝试了以下方法：
char str[1024];
char tmp = '.';
strcat(str, tmp);
But it does not work. It shows me the error: "passing argument 2 of ‘strcat' makes pointer from integer without a cast" I know that in C a char can be cast as int aswell. Do I have to convert the tmp to an char array aswell or is there a better solution?
但它不起作用。它向我显示了错误：“传递 'strcat' 的参数 2 使指针来自整数而不进行强制转换”我知道在 C 中，char 也可以被强制转换为 int。我是否还必须将 tmp 转换为字符数组，还是有更好的解决方案？
回答by Fantastic Mr Fox
strcathas the declaration:
strcat有声明：
char *strcat(char *dest, const char *src)
It expects 2 strings. While this compiles:
它需要 2 个字符串。虽然这编译：
char str[1024] = "Hello World";
char tmp = '.';
strcat(str, tmp);
It will cause bad memory issues because strcatis looking for a null terminated cstring. You can do this:
它会导致糟糕的内存问题，因为strcat正在寻找一个空终止的 cstring。你可以这样做：
char str[1024] = "Hello World";
char tmp[2] = ".";
strcat(str, tmp);
If you really want to append a char you will need to make your own function. Something like this:
如果您真的想附加一个字符，则需要创建自己的函数。像这样的东西：
void append(char* s, char c) {
int len = strlen(s);
s[len] = c;
s[len+1] = ' char *strcat(char *dest, const char *src);
';
}
append(str, tmp)
Of course you may also want to check your string size etc to make it memory safe.
当然，您可能还想检查字符串大小等以确保内存安全。
回答by P.P
The error is due the fact that you are passing a wrong to strcat(). Look at strcat()'s prototype:
该错误是由于您将错误传递给strcat(). 看一下strcat()原型：
char str[1024] = "Hello World";
char tmp = '.';
size_t len = strlen(str);
snprintf(str + len, sizeof str - len, "%c", tmp);
But you pass charas the second argument, which is obviously wrong.
但是你char作为第二个参数传递，这显然是错误的。
Use snprintf()instead.
使用snprintf()来代替。
char str[1024];
ch tmp = '.';
int i = 5;
// Fill str here
snprintf(str + len, sizeof str - len, "%c%d", str, tmp, i);
As commented by OP:
正如 OP 所评论的：
That was just a example with Hello World to describe the Problem. It must be empty as first in my real program. Program will fill it later. The problem just contains to add a char/int to an char Array
这只是一个用 Hello World 来描述问题的例子。在我的真实程序中，它必须是空的。程序稍后会填充它。问题仅包含将 char/int 添加到 char Array
In that case, snprintf()can handle it easily to "append" integer types to a char buffer too. The advantage of snprintf()is that it's more flexible to concatenate various types of data into a char buffer.
在这种情况下，snprintf()也可以轻松处理将整数类型“附加”到字符缓冲区。的优点snprintf()是可以更灵活地将各种类型的数据连接到一个字符缓冲区中。
For example to concatenate a string, char and an int:
例如连接字符串、字符和整数：
char str[1024] = "Hello World"; //this will add all characters and a NULL byte to the array
char tmp[2] = "."; //this is a string with the dot
strcat(str, tmp); //here you concatenate the two strings
回答by Riccardo Maffei
In C/C++ a string is an array of char terminated with a NULL byte ('\0');
在 C/C++ 中，字符串是一个以 NULL 字节 ( '\0')结尾的字符数组；
- Your string str has not been initialized.
- You must concatenate strings and you are trying to concatenate a single char (without the null byte so it's not a string) to a string.
- 您的字符串 str 尚未初始化。
- 您必须连接字符串，并且您正在尝试将单个字符（没有空字节，因此它不是字符串）连接到字符串。
The code should look like this:
代码应如下所示：
char str[1024];
str = "Hello World"; //FORBIDDEN
Note that you can assign a string literal to an array only during its declaration.
For example the following code is not permitted:
请注意，您只能在声明期间将字符串文字分配给数组。
例如，以下代码是不允许的：
char str[1024];
strcpy(str, "Hello World"); //here you copy "Hello World" inside the src array
and should be replaced with
并且应该替换为
char str[1024];
char tmp = '.';
strcat(str, tmp);
回答by user3629249
Suggest replacing this:
建议更换这个：
char str[1024] = {'char str[1024]; // Only declares size
char tmp = '.';
'}; // set array to initial all NUL bytes
char tmp[] = "."; // create a string for the call to strcat()
strcat(str, tmp); //
with this:
有了这个：
char str[1024] = "Hello World"; //Now you have "Hello World" in str
char tmp[2] = ".";
回答by Shondeslitch
I think you've forgotten initialize your string "str": You need initialize the string before using strcat. And also you need that tmp were a string, not a single char. Try change this:
我想你忘记了初始化你的字符串“str”：你需要在使用 strcat 之前初始化字符串。而且您还需要 tmp 是一个字符串，而不是单个字符。尝试改变这个：
##代码##for
为了
##代码##