Question

linux中read 如何从文件读取数据

Answer 1

#include <stdio.h>
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

ptr---读入的buf
size--读入的大小
nmenb--读入的数据块，取1
stream--文件指针

Answer 2

注意：以下实例省略了错误处理。
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

typedef struct
{
char name[20];
int age;
} Person;

int main(int argc, char **argv)
{
// open
int fd = open("name.file", O_RDWR|O_CREAT, 0666);
// write
Person zhang3;
memset((void*)&zhang3, 0x00, sizeof(Person));
strcpy(zhang3.name, "zhang3");
zhang3.age = 42;
write(fd, (void*)&zhang3, sizeof(Person));
// lseek
lseek(fd, 0, SEEK_SET);
// read
Person li4;
memset((void*)&li4, 0x00, sizeof(Person));
read(fd, (void*)&li4, sizeof(Person));
printf("%s\n", li4.name);
printf("%d\n", li4.age);
// close
close(fd);
return 0;
}