Linux api文件io和 c库标准io 实现文本字节数计算

linux api实现

代码

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int readFileSize_API(const char *pathname, int *fileSize);

int main(int argc, char *argv[])
{
	int fileSize = 0;
	if(2 != argc){
		printf("usage: format like \" argv[0] pathname\".\n");
		exit(EXIT_FAILURE);
	}
	
	if(!readFileSize_API(argv[1], &fileSize)){
		printf("文件 %s 的大小为：%d字节.\n", argv[1], fileSize);
	}
	return 0;
}

int readFileSize_API(const char *pathname, int *fileSize)
{
	int fd = -1;
	int size;
	
	fd = open(pathname, O_RDONLY);
	if(-1 == fd){
		printf("func:%s line:%d\n",__func__,__LINE__);
		fflush(stdout);
		perror("error");
		return -1;
	}
	
	size = lseek(fd, 0, SEEK_END);
	close(fd);
	*fileSize = size;	
	return 0;
}

结果示例：

# ./a.out a.out
文件 a.out 的大小为：7697字节.

标准IO实现

代码

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

int readFileSize_Stdio(const char *pathname, int *fileSize);

int main(int argc, char *argv[])
{
	int fileSize = 0;
	if(2 != argc){
		printf("usage: format like \" argv[0] pathname\".\n");
		exit(EXIT_FAILURE);
	}
	
	if(!readFileSize_Stdio(argv[1], &fileSize)){
		printf("文件 %s 的大小为：%d字节.\n", argv[1], fileSize);
	}
	return 0;
}

int readFileSize_Stdio(const char *pathname, int *fileSize)
{
	FILE *fd = NULL;
	int size;
	
	fd = fopen(pathname, "rb");	//以二进制流打开
	if(NULL == fd){
		printf("func:%s line:%d\n",__func__,__LINE__);
		fflush(stdout);
		perror("error");
		return -1;
	}
	
	fseek(fd, 0, SEEK_END);
	size = ftell(fd);
	close(fd);
	*fileSize = size;	
	return 0;
}

结果与api实现相同。