大家好，又见面了，我是你们的朋友全栈君。

注意

字符串格式化时不要，输入和输出参数不要使用同一个字符数组。
springt函数处理流程分析：

• 输入和输出参数不同sprintf(str2, “ab%s”,str)：
  

• 输入和输出参数相同sprintf(str, “ab%s”,str)：
  

示例

#include <stdio.h>

int main()
{ 
   
	char str[10] = "0123456789";
	char str2[10] = "";
	str[0] = 0;
	str[1] = 0;
	str[2] = 0;
	str[3] = 0;
	for(int i = 0;i<10;i++){ 
   
		printf("1-str_c[%d] = %c\n",i,str[i]);	
	}
	printf("1-str = %s\n",str);
	//str格式化到str2
	sprintf(str2, "ab%s",str);
	
	for(int i = 0;i<10;i++){ 
   
		printf("2-str2_c[%d] = %c\n",i,str2[i]);	
	}	
	printf("2-str2 = %s\n",str2);
	for(int i = 0;i<10;i++){ 
   
		printf("3-str_c[%d] = %c\n",i,str[i]);	
	}	
	printf("3-str = %s\n",str);
	//str格式化到str（注意：这个地方输出结果）
	sprintf(str, "ab%s",str);
	for(int i = 0;i<10;i++){ 
   
		printf("4-str_c[%d] = %c\n",i,str[i]);	
	}	
	printf("4-str = %s\n",str);
   	return(0);
}

下面是打印结果：

1-str_c[0] = 
1-str_c[1] = 
1-str_c[2] = 
1-str_c[3] = 
1-str_c[4] = 4
1-str_c[5] = 5
1-str_c[6] = 6
1-str_c[7] = 7
1-str_c[8] = 8
1-str_c[9] = 9
1-str = 
2-str2_c[0] = a
2-str2_c[1] = b
2-str2_c[2] = 
2-str2_c[3] = 
2-str2_c[4] = 
2-str2_c[5] = 
2-str2_c[6] = 
2-str2_c[7] = 
2-str2_c[8] = 
2-str2_c[9] = 
2-str2 = ab
3-str_c[0] = 
3-str_c[1] = 
3-str_c[2] = 
3-str_c[3] = 
3-str_c[4] = 4
3-str_c[5] = 5
3-str_c[6] = 6
3-str_c[7] = 7
3-str_c[8] = 8
3-str_c[9] = 9
3-str = 
4-str_c[0] = a
4-str_c[1] = b
4-str_c[2] = a
4-str_c[3] = b
4-str_c[4] = 
4-str_c[5] = 5
4-str_c[6] = 6
4-str_c[7] = 7
4-str_c[8] = 8
4-str_c[9] = 9
4-str = abab