File and Directory Operations

`open` and `openat`

Supported functionality of open in SCML:

access_mode =
    O_RDONLY |
    O_WRONLY |
    O_RDWR;
creation_flags =
    O_CLOEXEC |
    O_DIRECTORY |
    O_EXCL |
    O_NOCTTY |
    O_NOFOLLOW |
    O_TRUNC;
status_flags =
    O_APPEND |
    O_ASYNC |
    O_DIRECT |
    O_LARGEFILE |
    O_NOATIME |
    O_NONBLOCK |
    O_SYNC;

// Open an existing file
open(
    path,
    flags = <access_mode> | <creation_flags> | <status_flags>,
);
openat(
    dirfd,
    path,
    flags = <access_mode> | <creation_flags> | <status_flags>,
);

// Create a new file
open(
    path,
    flags = O_CREAT | <access_mode> | <creation_flags> | <status_flags>,
    mode
);
openat(
    dirfd,
    path,
    flags = O_CREAT | <access_mode> | <creation_flags> | <status_flags>,
    mode
);

// Status flags that are meaningful with O_PATH
opath_valid_flags = O_CLOEXEC | O_DIRECTORY | O_NOFOLLOW;
// All other flags are ignored with O_PATH
opath_ignored_flags = O_CREAT | <creation_flags> | <status_flags>;
// Obtain a file descriptor to indicate a location in FS
open(
    path,
    flags = O_PATH | <opath_valid_flags> | <opath_ignored_flags>
);
openat(
    dirfd,
    path,
    flags = O_PATH | <opath_valid_flags> | <opath_ignored_flags>
);

// Create an unnamed file
// open(path, flags = O_TMPFILE | <creation_flags> | <status_flags>)

Silently-ignored flags:

O_NOCTTY
O_DSYNC
O_SYNC
O_LARGEFILE
O_NOATIME
O_NOCTTY

Partially-supported flags:

O_PATH

未支援的旗標：

O_TMPFILE

Supported and unsupported functionality of openat are the same as open. The SCML rules are omitted for brevity.

For more information, see the man page.

`renameat2`

SCML 支援的功能：

// Rename a file, moving it between directories if required.
renameat2(olddirfd, oldpath, newdirfd, newpath, 0);

未支援的旗標：

RENAME_EXCHANGE
RENAME_NOREPLACE
RENAME_WHITEOUT

For more information, see the man page.

`lseek`

SCML 支援的功能：

// Set file offset
lseek(
    fd, offset,
    whence = SEEK_SET | SEEK_CUR | SEEK_END
);

未支援的旗標：

SEEK_DATA
SEEK_HOLE

For more information, see the man page.

`newfstatat`

SCML 支援的功能：

// Retrieve file status by file descriptor
newfstatat(
    dirfd, path, statbuf,
    flags = AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW
);

Silently-ignored flags:

AT_NO_AUTOMOUNT

For more information, see the man page.

`preadv2` and `pwritev2`

SCML 支援的功能：

// Read data from multiple buffers
preadv2(fd, iov, iovcnt, offset, flags = 0);

// Write data to multiple buffers
pwritev2(fd, iov, iovcnt, offset, flags = 0);

Silently-ignored flags:

RWF_DSYNC
RWF_HIPRI
RWF_SYNC
RWF_NOWAIT

未支援的旗標：

RWF_APPEND
RWF_NOAPPEND
RWF_ATOMIC

For more information, see the man page.

`faccessat2`

SCML 支援的功能：

// Check user's permissions for a file
faccessat2(
    dirfd, path, mode,
    flags = AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW
);

Silently-ignored flags:

AT_EACCESS

For more information, see the man page.

`statx`

SCML 支援的功能：

statx_flags = AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_STATX_FORCE_SYNC |
              AT_STATX_DONT_SYNC | AT_STATX_SYNC_AS_STAT | AT_SYMLINK_NOFOLLOW;
statx_mask = STATX_TYPE | STATX_MODE | STATX_NLINK | STATX_UID | STATX_GID |
             STATX_ATIME | STATX_MTIME | STATX_CTIME | STATX_INO | STATX_SIZE |
             STATX_BLOCKS | STATX_BASIC_STATS | STATX_BTIME | STATX_ALL |
             STATX_MNT_ID | STATX_DIOALIGN | STATX_MNT_ID_UNIQUE | STATX_SUBVOL |
             STATX_WRITE_ATOMIC | STATX_DIO_READ_ALIGN;

// Get file status (extended)
statx(
    dirfd, pathname,
    flags = <statx_flags>,
    mask = <statx_mask>,
    statxbuf
);

Silently-ignored flags:

AT_NO_AUTOMOUNT
AT_STATX_FORCE_SYNC
AT_STATX_DONT_SYNC

Silently-ignored masks:

STATX_DIOALIGN
STATX_MNT_ID_UNIQUE
STATX_SUBVOL
STATX_WRITE_ATOMIC
STATX_DIO_READ_ALIGN

For more information, see the man page.

`fallocate`

SCML 支援的功能：

// Allocate disk space within the range specified
fallocate(fd, mode = FALLOC_FL_KEEP_SIZE, offset, size);

// Deallocate space (create a hole) while keeping the file size unchanged
fallocate(fd, mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, offset, size);

未支援的模式：

FALLOC_FL_UNSHARE_RANGE
FALLOC_FL_COLLAPSE_RANGE
FALLOC_FL_ZERO_RANGE
FALLOC_FL_INSERT_RANGE

For more information, see the man page.

`utimensat`

SCML 支援的功能：

// Change file timestamps with nanosecond precision
utimensat(dirfd, path, times, flags = AT_SYMLINK_NOFOLLOW);

未支援的旗標：

AT_EMPTY_PATH

For more information, see the man page.

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