lseek操作

妖刀路过

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

#define  FILE1_NAME "lseek_test.c"
#define  FILE2_NAME "lseek_test2.txt"

#define  SIZE 100

int main(void) {
  int file1, file2;
  char buffer[1024];
  int ret;

  file1 = open(FILE1_NAME, O_RDONLY);
  if (file1 < 0) {
    printf("open file failed! reason:%s\n", strerror(errno));
    exit(-1);
  }

  file2 = open(FILE2_NAME, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
  if (file2 < 0) {
    printf("open file failed! reason:%s\n", strerror(errno));
    exit(-2);
  }

  //文件句柄，偏移量，从哪偏移

  ret = lseek(file1, 0, SEEK_END);
  printf("file size: %d\n", ret);

  ret = lseek(file1, 100, SEEK_SET);
  printf("lseek ret:%d\n", ret);

  ret = read(file1, buffer, SIZE);
  if (ret > 0) {
    buffer[ret] = '\0';
    write(file2,buffer,SIZE);
  }

  close(file1);
  close(file2);


  return 0;
}