CSAPP笔记（十） 系统级I/O

深入理解计算机系统

Unix I/O

open(const char *pathname, int flags, mode_t mode);
O_RDONLY, O_WRONLY, O_RDWR
S_IRWXU, S_IRUSR, S_IWUSR
read(int fd, void *buf, size_t count);
write(int fd, const void *buf, size_t count);
stat(const char *pathname, struct stat *statbuf);

struct stat {
    dev_t st_dev; // Device
    ino_t st_ino; // inode
    mode_t st_mode; // Protection and file type
    nlink_t st_nlink; // Number of hard links
    uid_t st_uid; // User ID of owner
    gid_t st_gid; // Group ID of owner
    dev_t st_rdev; // Device type (if inode device)
    off_t st_size; // Total size, in bytes
    unsigned long st_blksize; // Blocksize for filesystem I/O
    unsigned long st_blocks; // Number of blocks allocated
    time_t st_atime; // Time of last access
    time_t st_mtime; // Time of last modification
    time_t st_ctime; // Time of last change
};

共享文件

共享文件
描述符表是进程独有
文件位置（file position）:文件头起始的偏移量

重定向

dup2(int oldfd, int newfd);
ls > text.txt STDOUT_FILENO指向 text.txt
ls < text.txt STDIN_FILENO指向 text.txt