fprintf和fwrite的一点“怪异”现象- C

我们先来看一个简单的程序：


#include<stdio.h>
 
int main()
{
	int a = 0;
	int len = sizeof(a);
 
	// 相当于在log1中以文本文件方式输入0
	// 文件对应的比特串实际为00110000
	FILE *fp1 = fopen("log1", "w");
	fprintf(fp1, "%d", a);
	fclose(fp1);
 
	// 文件对应的比特串实际为00000000000000000000000000000000
	FILE *fp2 = fopen("log2", "wb");
	fwrite(&a, len, 1, fp2);
	fclose(fp2);
 
	return 0;
}

同样是为了存一个整数0，log1和log2是不一样的，这是正常的。下面，我们来继续看程序：


#include<stdio.h>
 
int main()
{
	char c = 'a';
	int len = sizeof(c);
 
	FILE *fp1 = fopen("log1", "w");
	fprintf(fp1, "%c", c);
	fclose(fp1);
 
	FILE *fp2 = fopen("log2", "wb");
	fwrite(&c, len, 1, fp2);
	fclose(fp2);
 
	return 0;
}

结果，log1和log2居然是一样的，大家可以思考一下为什么。接着看程序：


#include<stdio.h>
#include<string.h>
 
int main()
{
	char s[] = "hello world";
	int len = strlen("hello world");
 
	FILE *fp1 = fopen("log1", "w");
	fprintf(fp1, "%s", s);
	fclose(fp1);
 
	FILE *fp2 = fopen("log2", "wb");
	fwrite(s, len, 1, fp2);
	fclose(fp2);
 
	return 0;
}

结果，log1和log2居然也是一样的，原因与上类似。

可见，在针对字符和字符串时候，fwrite写了之后，实际上还是文本文件。

我们再看程序：


#include<stdio.h>
 
int main()
{
	int a = 9;
	int len = sizeof(a);
 
	FILE *fp1 = fopen("log1", "wb");
	fwrite(&a, len, 1, fp1);
	fclose(fp1);
 
	// fwrite最好不要和"w"混用
	FILE *fp2 = fopen("log2", "w");
	fwrite(&a, len, 1, fp2);
	fclose(fp2);
 
	return 0;
}

结果，log1和log2完全一样。继续看下面程序：


#include<stdio.h>
#include<string.h>
 
int main()
{
	char s[] = "hello world";
	int len = strlen("hello world");
 
	FILE *fp1 = fopen("log1", "w");
	fprintf(fp1, "%s", s);
	fclose(fp1);
 
	FILE *fp2 = fopen("log2", "wb");
	fwrite(s, len, 1, fp2);
	fclose(fp2);
 
	// fwrite最好不要和"w"混用
	FILE *fp3 = fopen("log3", "w");
	fwrite(s, len, 1, fp3);
	fclose(fp3);
 
	return 0;
}