What does %r mean in c language

In C language, the %r conversion specifier is used for: Formatted output: Print the address of a pointer variable, and the result is usually displayed in hexadecimal format. Formatted input: Read and store the input address into a pointer variable.

%r in C language is the conversion specifier for formatted output

%r is in C language Formatted output and input conversion specifiers commonly used in the printf() and scanf() functions. It is used to print or read the value of a pointer.

Formatted output (printf() function):

• Usage: printf("%r", &variable);
• Effect: Print the address of the variable.

Formatted input (scanf() function):

• Usage: scanf("%r", &variable );
• Effect:Read an address from the input and store it in the variable.

Note: The

• %r conversion specifier only applies to pointer variables.
• When printing pointer variables, the output results will vary depending on the compiler and platform. Addresses are usually printed in hexadecimal format.
• When reading a pointer variable, the input must be a valid memory address. Otherwise, the read operation will fail.

Example:

<code class="c">int main() {
    int *ptr = malloc(sizeof(int));
    *ptr = 10;

    printf("Pointer value: %r\n", ptr);  // 输出指针地址
    scanf("%r", &ptr);  // 从输入中读取指针地址

    printf("Dereferenced pointer value: %d\n", *ptr);  // 输出通过指针访问的值

    return 0;
}</code>

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