C language removes line breaks (or other characters) at the end of strings

void main()
{
    
	char now_mac[100];
	strcpy(now_mac, "abcd\n"); // \0 End of string （strlen Not counting length ）,\n For newline （strlen count 1 Length ）
	printf("%d\n", strlen(now_mac)); //  Output 5
	// now_mac[strlen(now_mac) - 1] = 0; //  take \n Directly replace with 0 The effect is the same 
	now_mac[strlen(now_mac) - 1] = '\0'; //  take \n Replace with \0
	printf("%d\n", strlen(now_mac)); //  Output 4
}

Reference link ：
C Remove end of string newline （ Remove the last character of the string ）