# Struct std::fs::Permissions

1.0.0 · source ·

    pub struct Permissions(/* private fields */);

Expand description

Representation of the various permissions on a file.

This module only currently provides one bit of information, `Permissions::readonly`, which is exposed on all currently supported platforms. Unix-specific functionality, such as mode bits, is available through the `PermissionsExt` trait.

## Implementations§

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### impl Permissions

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#### pub fn readonly(&self) -> bool

Returns `true` if these permissions describe a readonly (unwritable) file.

##### Note

This function does not take Access Control Lists (ACLs) or Unix group membership into account.

##### Windows

On Windows this returns `FILE_ATTRIBUTE_READONLY`. If `FILE_ATTRIBUTE_READONLY` is set then writes to the file will fail but the user may still have permission to change this flag. If `FILE_ATTRIBUTE_READONLY` is not set then writes may still fail due to lack of write permission. The behavior of this attribute for directories depends on the Windows version.

##### Unix (including macOS)

On Unix-based platforms this checks if any of the owner, group or others write permission bits are set. It does not check if the current user is in the file’s assigned group. It also does not check ACLs. Therefore even if this returns true you may not be able to write to the file, and vice versa. The `PermissionsExt` trait gives direct access to the permission bits but also does not read ACLs. If you need to accurately know whether or not a file is writable use the `access()` function from libc.

##### Examples

    use std::fs::File;

    fn main() -> std::io::Result<()> {
        let mut f = File::create("foo.txt")?;
        let metadata = f.metadata()?;

        assert_eq!(false, metadata.permissions().readonly());
        Ok(())
    }

Run
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#### pub fn set_readonly(&mut self, readonly: bool)

Modifies the readonly flag for this set of permissions. If the `readonly` argument is `true`, using the resulting `Permission` will update file permissions to forbid writing. Conversely, if it’s `false`, using the resulting `Permission` will update file permissions to allow writing.

This operation does not modify the files attributes. This only changes the in-memory value of these attributes for this `Permissions` instance. To modify the files attributes use the `set_permissions` function which commits these attribute changes to the file.

##### Note

`set_readonly(false)` makes the file world-writable on Unix. You can use the `PermissionsExt` trait on Unix to avoid this issue.

It also does not take Access Control Lists (ACLs) or Unix group membership into account.

##### Windows

On Windows this sets or clears `FILE_ATTRIBUTE_READONLY`. If `FILE_ATTRIBUTE_READONLY` is set then writes to the file will fail but the user may still have permission to change this flag. If `FILE_ATTRIBUTE_READONLY` is not set then the write may still fail if the user does not have permission to write to the file.

In Windows 7 and earlier this attribute prevents deleting empty directories. It does not prevent modifying the directory contents. On later versions of Windows this attribute is ignored for directories.

##### Unix (including macOS)

On Unix-based platforms this sets or clears the write access bit for the owner, group and others, equivalent to `chmod a+w <file>` or `chmod a-w <file>` respectively. The latter will grant write access to all users! You can use the `PermissionsExt` trait on Unix to avoid this issue.

##### Examples

    use std::fs::File;

    fn main() -> std::io::Result<()> {
        let f = File::create("foo.txt")?;
        let metadata = f.metadata()?;
        let mut permissions = metadata.permissions();

        permissions.set_readonly(true);

        // filesystem doesn't change, only the in memory state of the
        // readonly permission
        assert_eq!(false, metadata.permissions().readonly());

        // just this particular `permissions`.
        assert_eq!(true, permissions.readonly());
        Ok(())
    }

Run

## Trait Implementations§

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### impl Clone for Permissions

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#### fn clone(&self) -> Permissions

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for Permissions

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl PartialEq for Permissions

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#### fn eq(&self, other: &Permissions) -> bool

This method tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.1.0 · source§

### impl PermissionsExt for Permissions

Available on Unix only.
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#### fn mode(&self) -> u32

Returns the underlying raw `st_mode` bits that contain the standard Unix permissions for this file. Read more
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#### fn set_mode(&mut self, mode: u32)

Sets the underlying raw bits for this set of permissions. Read more
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#### fn from_mode(mode: u32) -> Permissions

Creates a new instance of `Permissions` from the given set of Unix permission bits. Read more
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### impl Eq for Permissions

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### impl StructuralEq for Permissions

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### impl StructuralPartialEq for Permissions

## Auto Trait Implementations§

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### impl RefUnwindSafe for Permissions

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### impl Send for Permissions

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### impl Sync for Permissions

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### impl Unpin for Permissions

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### impl UnwindSafe for Permissions

## Blanket Implementations§

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### impl<T> Any for Twhere T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for Twhere T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for Twhere T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for Twhere U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for Twhere T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.