c - 如何在c中显示printf语句的行号？

Question

int main() {
int i, repeatName; // ints
char firstName[50]; // array to store users name

// get first name from user
printf("Please enter your first name: ");
scanf("%s", firstName);

// get amount of times user would like to repeat name
printf("How many times would you like to repeat your name?: ");
scanf("%i", &repeatName);

// tell user name has to be repeated at last one
if (repeatName < 1) {
    printf("The name has to be repeated at least one (1) time. Try again: ");
    scanf("%i", &repeatName);
}

// for loop to repeat name 'x' number of times
for (i = 0; i < repeatName; i++) {
    printf("%s \n", firstName);
}
}

例如:如果用户想要显示自己的名字 3 次，则会显示:

Your name 

Your name

Your name 

我怎样才能让它说:

Line 1 Your name

Line 2 Your name

Line 3 Your name 

Answer 1

在循环中使用i变量作为行号

for (i = 0; i < repeatName; ++i)
    printf("Line %d %s\n", i + 1, firstName);

请务必添加 1，因为循环索引从 0 开始。您希望第一行显示“Line 1”，而不是“Line 0”，依此类推。

编辑:当行号超过一位数字时，输出不太漂亮。为了解决这个问题，你可以这样写

for (i = 0; i < repeatName; ++i)
    printf("Line %-6d%s\n", i + 1, firstName);

这使得行号至少占用 6 个字符，并且使行号左对齐:

Line 1     this is my string
Line 2     this is my string
Line 3     this is my string
Line 4     this is my string
Line 5     this is my string
Line 6     this is my string
Line 7     this is my string
Line 8     this is my string
Line 9     this is my string
Line 10    this is my string