文件IO练习

一、用read函数完成文件大小计算

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, const char *argv[])
{int fd = open("./1.txt",O_RDONLY);if(fd < 0){perror("open");return -1;}printf("open success!\n");off_t size = lseek(fd,0,SEEK_END);printf("size=%ld\n",size);char c;ssize_t res = 0;int count = 0;lseek(fd,0,SEEK_SET);while(1){res = read(fd,&c,1);if(0 == res)break;count++;}printf("count=%d\n",count);if(close(fd) < 0){perror("close");return -1;} printf("close success!\n");return 0;
}

二、将文件权限提取修改成循环方式

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
void get_filePermission(mode_t m)
{long x = 0400;char c[]="rwx";int count = 0; while(x){if((m & x) == 0)putchar('-');elseprintf("%c",c[count%3]);count++;x = x >> 1;}putchar(' ');
}
int main(int argc, const char *argv[])
{struct stat buf;if(stat("./1.txt",&buf) < 0){perror("stat");return -1;}printf("0%o ",buf.st_mode);get_filePermission(buf.st_mode);printf("%ld ",buf.st_nlink);printf("%d ",buf.st_uid);printf("%d ",buf.st_gid);printf("%ld ",buf.st_size);struct tm *info=NULL;info = localtime(&buf.st_mtime);
//	printf("%ld ",buf.st_ctime);printf("%d-%02d-%02d %02d:%02d:%02d\n",info->tm_year+1900,info->tm_mon+1,info->tm_mday,info->tm_hour,info->tm_min,info->tm_sec);return 0;
}