C语言的文件函数

stream表示流

1：fputs

int fputs(int character,FILE* stream);

#include<stdio.h>

int main()
{
	FILE* pf=fopen("data.txt", "w");
	//打开判断是否成功
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	fputc('a', pf);
	fputc('a', pf);
	fputc('a', pf);
	fputc('a', pf);
	fputc('a', pf);
	//关闭
	fclose(pf);
	pf == NULL;
	return 0;
}

fputc的第二个是字符，不是字符串。

2：fgetc

int getc(FILE* stream);

使用int类型来接收返回值，是因为如果返回错误就算返回-1（EOF）

int main()
{
	FILE* pf = fopen("data.txt", "r");
	//打开判断是否成功
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	int ch = fgetc(pf);
    printf("%c\n",ch);
	//关闭
	fclose(pf);
	pf == NULL;
	return 0;
}

ch表示一次接受一个字符

3：fputs

    int fputs(const char* str, FILE * stream);

int main()
{
		FILE* pf = fopen("data.txt", "w");
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	fputs("i ilke c", pf);
	fclose(pf);
	pf = NULL;
	return 0;
}

4：fgets

char* fgets(char* str, int num, FILE * stream);

int main()
{
	char str[100];
	fgets(str,100,stdin);
	printf("%s", str);
	return 0;
}

5：fprintf

    int fprintf(FILE * stream, const char* format, ...);

int main()
{
	struct st
	{
		int age;
		char name[100];
		char sex[10];
    };
	struct st s = { 10,"xiaogang","boy" };
			FILE* pf = fopen("data.txt", "w");
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	fprintf(pf, "%d %s %s", s.age, s.name, s.sex);
	return 0;
}

6：fscanf

    int fscanf(FILE * stream, const char* format, ...);

int main()
{
	FILE* pf = fopen("data.txt","r");
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	int age;
	char name[100];
	char sex[100];
	fscanf(pf, "%d %s %s", &age, name, sex);
	printf("%d %s %s", age, name, sex);
	return 0;
}

7：fread和fwrite（二进制输入和输出）

ferad：    size_t fread(void* ptr, size_t size, size_t count, FILE * stream);

fwrite：    size_t fwrite(const void* ptr, size_t size, size_t count, FILE * stream);

int main()
{
	//fwrite
	FILE* pf = fopen("data.txt", "wb");
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	int arr[] = { 1,2,3,4,5,6,7,8,9 };
	fwrite(arr,sizeof(int),10,pf);
	fclose(pf);
	pf = NULL;
	//fread
	FILE* pf2 = fopen("data.txt", "rb");
	if (pf2 == NULL)
	{
		perror("fopen");
		return 1;
	}
	int arr2[10] = { 0 };
	fread(arr2, sizeof(int), 10, pf2);
	for (int i = 0; i < 9; i++)
	{
		printf("%d ",arr2[i]);
	}
	fclose(pf2);
	pf2 = NULL;
	return 0;
}

8:fseek

int fseek ( FILE * stream, long int offset, int origin );

int main()
{
		FILE* pFile;
		pFile = fopen("example.txt", "wb");
		fputs("This is an apple.", pFile);
		fseek(pFile, 9, SEEK_SET);
		fputs(" sam", pFile); 
		fclose(pFile);
	return 0;
}

9:ftell

long int ftell ( FILE * stream );

#include <stdio.h>
int main ()
{
 FILE * pFile;
 long size;
 pFile = fopen ("myfile.txt","rb");
 if (pFile==NULL) 
 perror ("Error opening file");
 else
 {
 fseek (pFile, 0, SEEK_END); // non-portable
 size=ftell (pFile);
 fclose (pFile);
 printf ("Size of myfile.txt: %ld bytes.\n",size);
 }
 return 0;
}

10:rewind

让文件指针位置回到起始位置

int main()
{
	FILE* pFile;
	long size;
	pFile = fopen("example.txt", "rb");
	if (pFile == NULL)
		perror("Error opening file");
	else
	{
		fseek(pFile, 0, SEEK_END); // non-portable
		size = ftell(pFile);
		printf("Size of example.txt: %ld bytes.\n", size);
		rewind(pFile);
		fseek(pFile, 0, SEEK_END); // non-portable
		size = ftell(pFile);
		fclose(pFile);
		printf("Size of example.txt: %ld bytes.\n", size);
	}
	return 0;
}

11：feof（只能检测是否遇到文件末尾）