#include <stdio.h> #include <errno.h> int main() { close(1); // 打开一个文件 int fd = open ("test.txt", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR | S_IXUSR); //int fd = open ("test.txt", O_RDONLY); if (fd == -1) { printf ("打开文件失败\n"); perror ("open"); printf ("%s\n", strerror(errno)); } printf ("fd = %d\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); printf ("asdadasdad\n", fd); // fflush(stdout); close(fd); return 0; }
#include <sys/types.h>
#include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <string.h> #include <errno.h> #define SIZE 1024 int main1() { int fd = open("BTree.c", O_RDONLY, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; ssize_t ret = read(fd, buf, SIZE-1); if (ret == -1) { perror ("read"); } // 返回值为0 代表读到文件结尾 if (ret == 0) { printf ("文件读取结束\n"); } printf ("len = %d\n", strlen(buf)); printf ("读到 %d 字节： %s\n", ret, buf); return 0; } // 缓冲区覆盖问题 int main2() { int fd = open("BTree.c", O_RDONLY, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; while (1) { ssize_t ret = read(fd, buf, SIZE-1); if (ret == -1) { perror ("read"); } // 返回值为0 代表读到文件结尾 if (ret == 0) { printf ("文件读取结束\n"); break; } //printf ("len = %d\n", strlen(buf)); // printf ("读到 %d 字节： %s\n", ret, buf); printf ("%s", buf); } return 0; } // 读取数据之前清空缓冲区 int main3() { int fd = open("BTree.c", O_RDONLY, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; while (1) { memset (buf, 0, SIZE); // 清空缓冲区 ssize_t ret = read(fd, buf, SIZE-1); if (ret == -1) { perror ("read"); } if (ret == 0) { printf ("文件读取结束\n"); break; } printf ("%s", buf); } return 0; } // 每次读完数据之后将下一个字节置为 '\0'; int main4() { int fd = open("BTree.c", O_RDONLY, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; while (1) { ssize_t ret = read(fd, buf, SIZE-1); if (ret == -1) { perror ("read"); } if (ret == 0) { printf ("文件读取结束\n"); break; } buf[ret] = '\0'; printf ("%s", buf); } return 0; } // 读一个完整的大数据 int main() { int fd = open("BTree.c", O_RDONLY, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; char *p = buf; int count = SIZE-1; // 每一次要读的数据个数 ssize_t ret = 0; while (ret = read(fd, p, count)) { // 出错 if (ret == -1) { if (errno == EAGAIN || errno == EINTR) { continue; } break; } printf ("asdasdsadsa\n"); // 读完 if (count == ret) { break; } count -= ret; // 下一次要读的数据 p += ret; } printf ("len = %d\n", strlen(buf)); //printf ("%s\n", buf); return 0;}
#include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #define SIZE 1024 int main() { int fd = open("abc", O_WRONLY|O_CREAT, 0777); if (fd == -1) { perror ("open"); return -1; } char buf[SIZE] = {0}; while (1) { fgets (buf, SIZE, stdin); if (strncmp ("end", buf, 3) == 0) break; ssize_t ret = write(fd, buf, strlen(buf)); if (ret == -1) { perror ("write"); } printf ("要写的字节数 ：%d, 实际写的字节数： %d\n", SIZE, ret); } close(fd); return 0; }
