sprintf()用来格式化字符串。

示例：

//Visual Studio中加上这句才可以使用scanf()
//否则只能使用scanf_s()
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

#define MAX 20
char * s_gets(char * st, int n);

//argc: 参数个数 argv[]: 参数数组
int main(int argc, char *argv[])
{
	char first[MAX];
	char last[MAX];
	char formal[2 * MAX + 10];
	double prize;

	puts("Enter your first name:");
	s_gets(first, MAX);
	puts("Enter your last name:");
	s_gets(last, MAX);
	puts("Enter your prize money:");
	scanf("%lf", &prize);
	//格式化字符串
	sprintf(formal, "%s, %-19s: $%6.2f\n", last, first, prize);
	puts(formal);

	system("pause");
	return 0;
}

char * s_gets(char * st, int n)
{
	char * ret_val;
	int i = 0;
	ret_val = fgets(st, n, stdin);
	if (ret_val) //即，ret_val != NULL
	{
		while (st[i] != '\n' && st[i] != '\0')
			i++;
		if (st[i] == '\n')
			st[i] = '\0';
		else
			while (getchar() != '\n')
				continue;
	}
	return ret_val;
}

运行测试