[C][string] fprintf/sprintf用法

●fprintf: 輸入格式化的文字到文件中

file printf

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    FILE *fPtr;
    int age = 20;
    
    fPtr = fopen("test.txt", "w");
    if (!fPtr) {
        printf("open file fail\n");
        return 0;
    }
    
    fprintf(fPtr, "I am %d years old.\n", age );
   
    fclose(fPtr);
    
    return 0;
}

test.txt →  I am 20 years old.

----

●sprintf: 輸入格式化的文字到字串中

string printf

snprintf: n表示多帶了buffer大小,避免溢位.

#include <stdio.h>
#include <math.h>

int main()
{
   char str[80];

   sprintf(str, "Hello %d", 123);
   //sprintf(str, sizeof(str),"Hello %d", 123);

   puts(str);
   
   return(0);
}

str → Hello 123