
.. _fs:

Filesystem operations
=====================

libuv provides a wide variety of cross-platform sync and async filesystem
operations. All functions defined in this document take a callback, which is
allowed to be NULL. If the callback is NULL the request is completed synchronously,
otherwise it will be performed asynchronously.

All file operations are run on the threadpool, see :ref:`threadpool` for information
on the threadpool size.


Data types
----------

.. c:type:: uv_fs_t

    Filesystem request type.

.. c:type:: uv_timespec_t

    Portable equivalent of ``struct timespec``.

    ::

        typedef struct {
            long tv_sec;
            long tv_nsec;
        } uv_timespec_t;

.. c:type:: uv_stat_t

    Portable equivalent of ``struct stat``.

    ::

        typedef struct {
            uint64_t st_dev;
            uint64_t st_mode;
            uint64_t st_nlink;
            uint64_t st_uid;
            uint64_t st_gid;
            uint64_t st_rdev;
            uint64_t st_ino;
            uint64_t st_size;
            uint64_t st_blksize;
            uint64_t st_blocks;
            uint64_t st_flags;
            uint64_t st_gen;
            uv_timespec_t st_atim;
            uv_timespec_t st_mtim;
            uv_timespec_t st_ctim;
            uv_timespec_t st_birthtim;
        } uv_stat_t;

.. c:type:: uv_fs_type

    Filesystem request type.

    ::

        typedef enum {
            UV_FS_UNKNOWN = -1,
            UV_FS_CUSTOM,
            UV_FS_OPEN,
            UV_FS_CLOSE,
            UV_FS_READ,
            UV_FS_WRITE,
            UV_FS_SENDFILE,
            UV_FS_STAT,
            UV_FS_LSTAT,
            UV_FS_FSTAT,
            UV_FS_FTRUNCATE,
            UV_FS_UTIME,
            UV_FS_FUTIME,
            UV_FS_ACCESS,
            UV_FS_CHMOD,
            UV_FS_FCHMOD,
            UV_FS_FSYNC,
            UV_FS_FDATASYNC,
            UV_FS_UNLINK,
            UV_FS_RMDIR,
            UV_FS_MKDIR,
            UV_FS_MKDTEMP,
            UV_FS_RENAME,
            UV_FS_SCANDIR,
            UV_FS_LINK,
            UV_FS_SYMLINK,
            UV_FS_READLINK,
            UV_FS_CHOWN,
            UV_FS_FCHOWN,
            UV_FS_REALPATH
        } uv_fs_type;

.. c:type:: uv_dirent_t

    Cross platform (reduced) equivalent of ``struct dirent``.
    Used in :c:func:`uv_fs_scandir_next`.

    ::

        typedef enum {
            UV_DIRENT_UNKNOWN,
            UV_DIRENT_FILE,
            UV_DIRENT_DIR,
            UV_DIRENT_LINK,
            UV_DIRENT_FIFO,
            UV_DIRENT_SOCKET,
            UV_DIRENT_CHAR,
            UV_DIRENT_BLOCK
        } uv_dirent_type_t;

        typedef struct uv_dirent_s {
            const char* name;
            uv_dirent_type_t type;
        } uv_dirent_t;


Public members
^^^^^^^^^^^^^^

.. c:member:: uv_loop_t* uv_fs_t.loop

    Loop that started this request and where completion will be reported.
    Readonly.

.. c:member:: uv_fs_type uv_fs_t.fs_type

    FS request type.

.. c:member:: const char* uv_fs_t.path

    Path affecting the request.

.. c:member:: ssize_t uv_fs_t.result

    Result of the request. < 0 means error, success otherwise. On requests such
    as :c:func:`uv_fs_read` or :c:func:`uv_fs_write` it indicates the amount of
    data that was read or written, respectively.

.. c:member:: uv_stat_t uv_fs_t.statbuf

    Stores the result of :c:func:`uv_fs_stat` and other stat requests.

.. c:member:: void* uv_fs_t.ptr

    Stores the result of :c:func:`uv_fs_readlink` and serves as an alias to
    `statbuf`.

.. seealso:: The :c:type:`uv_req_t` members also apply.


API
---

.. c:function:: void uv_fs_req_cleanup(uv_fs_t* req)

    Cleanup request. Must be called after a request is finished to deallocate
    any memory libuv might have allocated.

.. c:function:: int uv_fs_close(uv_loop_t* loop, uv_fs_t* req, uv_file file, uv_fs_cb cb)

    Equivalent to :man:`close(2)`.

.. c:function:: int uv_fs_open(uv_loop_t* loop, uv_fs_t* req, const char* path, int flags, int mode, uv_fs_cb cb)

    Equivalent to :man:`open(2)`.

    .. note::
        On Windows libuv uses `CreateFileW` and thus the file is always opened
        in binary mode. Because of this the O_BINARY and O_TEXT flags are not
        supported.

.. c:function:: int uv_fs_read(uv_loop_t* loop, uv_fs_t* req, uv_file file, const uv_buf_t bufs[], unsigned int nbufs, int64_t offset, uv_fs_cb cb)

    Equivalent to :man:`preadv(2)`.

.. c:function:: int uv_fs_unlink(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)

    Equivalent to :man:`unlink(2)`.

.. c:function:: int uv_fs_write(uv_loop_t* loop, uv_fs_t* req, uv_file file, const uv_buf_t bufs[], unsigned int nbufs, int64_t offset, uv_fs_cb cb)

    Equivalent to :man:`pwritev(2)`.

.. c:function:: int uv_fs_mkdir(uv_loop_t* loop, uv_fs_t* req, const char* path, int mode, uv_fs_cb cb)

    Equivalent to :man:`mkdir(2)`.

    .. note::
        `mode` is currently not implemented on Windows.

.. c:function:: int uv_fs_mkdtemp(uv_loop_t* loop, uv_fs_t* req, const char* tpl, uv_fs_cb cb)

    Equivalent to :man:`mkdtemp(3)`.

    .. note::
        The result can be found as a null terminated string at `req->path`.

.. c:function:: int uv_fs_rmdir(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)

    Equivalent to :man:`rmdir(2)`.

.. c:function:: int uv_fs_scandir(uv_loop_t* loop, uv_fs_t* req, const char* path, int flags, uv_fs_cb cb)
.. c:function:: int uv_fs_scandir_next(uv_fs_t* req, uv_dirent_t* ent)

    Equivalent to :man:`scandir(3)`, with a slightly different API. Once the callback
    for the request is called, the user can use :c:func:`uv_fs_scandir_next` to
    get `ent` populated with the next directory entry data. When there are no
    more entries ``UV_EOF`` will be returned.

    .. note::
        Unlike `scandir(3)`, this function does not return the "." and ".." entries.

    .. note::
        On Linux, getting the type of an entry is only supported by some filesystems (btrfs, ext2,
        ext3 and ext4 at the time of this writing), check the :man:`getdents(2)` man page.

.. c:function:: int uv_fs_stat(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)
.. c:function:: int uv_fs_fstat(uv_loop_t* loop, uv_fs_t* req, uv_file file, uv_fs_cb cb)
.. c:function:: int uv_fs_lstat(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)

    Equivalent to :man:`stat(2)`, :man:`fstat(2)` and :man:`lstat(2)` respectively.

.. c:function:: int uv_fs_rename(uv_loop_t* loop, uv_fs_t* req, const char* path, const char* new_path, uv_fs_cb cb)

    Equivalent to :man:`rename(2)`.

.. c:function:: int uv_fs_fsync(uv_loop_t* loop, uv_fs_t* req, uv_file file, uv_fs_cb cb)

    Equivalent to :man:`fsync(2)`.

.. c:function:: int uv_fs_fdatasync(uv_loop_t* loop, uv_fs_t* req, uv_file file, uv_fs_cb cb)

    Equivalent to :man:`fdatasync(2)`.

.. c:function:: int uv_fs_ftruncate(uv_loop_t* loop, uv_fs_t* req, uv_file file, int64_t offset, uv_fs_cb cb)

    Equivalent to :man:`ftruncate(2)`.

.. c:function:: int uv_fs_sendfile(uv_loop_t* loop, uv_fs_t* req, uv_file out_fd, uv_file in_fd, int64_t in_offset, size_t length, uv_fs_cb cb)

    Limited equivalent to :man:`sendfile(2)`.

.. c:function:: int uv_fs_access(uv_loop_t* loop, uv_fs_t* req, const char* path, int mode, uv_fs_cb cb)

    Equivalent to :man:`access(2)` on Unix. Windows uses ``GetFileAttributesW()``.

.. c:function:: int uv_fs_chmod(uv_loop_t* loop, uv_fs_t* req, const char* path, int mode, uv_fs_cb cb)
.. c:function:: int uv_fs_fchmod(uv_loop_t* loop, uv_fs_t* req, uv_file file, int mode, uv_fs_cb cb)

    Equivalent to :man:`chmod(2)` and :man:`fchmod(2)` respectively.

.. c:function:: int uv_fs_utime(uv_loop_t* loop, uv_fs_t* req, const char* path, double atime, double mtime, uv_fs_cb cb)
.. c:function:: int uv_fs_futime(uv_loop_t* loop, uv_fs_t* req, uv_file file, double atime, double mtime, uv_fs_cb cb)

    Equivalent to :man:`utime(2)` and :man:`futime(2)` respectively.

    .. note::
      AIX: This function only works for AIX 7.1 and newer. It can still be called on older
      versions but will return ``UV_ENOSYS``.

    .. versionchanged:: 1.10.0 sub-second precission is supported on Windows

.. c:function:: int uv_fs_link(uv_loop_t* loop, uv_fs_t* req, const char* path, const char* new_path, uv_fs_cb cb)

    Equivalent to :man:`link(2)`.

.. c:function:: int uv_fs_symlink(uv_loop_t* loop, uv_fs_t* req, const char* path, const char* new_path, int flags, uv_fs_cb cb)

    Equivalent to :man:`symlink(2)`.

    .. note::
        On Windows the `flags` parameter can be specified to control how the symlink will
        be created:

            * ``UV_FS_SYMLINK_DIR``: indicates that `path` points to a directory.

            * ``UV_FS_SYMLINK_JUNCTION``: request that the symlink is created
              using junction points.

.. c:function:: int uv_fs_readlink(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)

    Equivalent to :man:`readlink(2)`.

.. c:function:: int uv_fs_realpath(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_fs_cb cb)

    Equivalent to :man:`realpath(3)` on Unix. Windows uses `GetFinalPathNameByHandle <https://msdn.microsoft.com/en-us/library/windows/desktop/aa364962(v=vs.85).aspx>`_.

    .. warning::
        This function has certain platform specific caveats that were discovered when used in Node.

        * macOS and other BSDs: this function will fail with UV_ELOOP if more than 32 symlinks are
          found while resolving the given path.  This limit is hardcoded and cannot be sidestepped.
        * Windows: while this function works in the common case, there are a number of corner cases
          where it doesn't:

          - Paths in ramdisk volumes created by tools which sidestep the Volume Manager (such as ImDisk)
            cannot be resolved.
          - Inconsistent casing when using drive letters.
          - Resolved path bypasses subst'd drives.

        While this function can still be used, it's not recommended if scenarios such as the
        above need to be supported.

        The background story and some more details on these issues can be checked
        `here <https://github.com/nodejs/node/issues/7726>`_.

    .. note::
      This function is not implemented on Windows XP and Windows Server 2003.
      On these systems, UV_ENOSYS is returned.

    .. versionadded:: 1.8.0

.. c:function:: int uv_fs_chown(uv_loop_t* loop, uv_fs_t* req, const char* path, uv_uid_t uid, uv_gid_t gid, uv_fs_cb cb)
.. c:function:: int uv_fs_fchown(uv_loop_t* loop, uv_fs_t* req, uv_file file, uv_uid_t uid, uv_gid_t gid, uv_fs_cb cb)

    Equivalent to :man:`chown(2)` and :man:`fchown(2)` respectively.

    .. note::
        These functions are not implemented on Windows.

.. seealso:: The :c:type:`uv_req_t` API functions also apply.
