Struct serde::lib::core::fs::Permissions

1.0.0 · source ·
pub struct Permissions(FilePermissions);
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.

Tuple Fields

0: FilePermissions

Implementations

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(())
}

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(())
}

Trait Implementations

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
Returns the underlying raw st_mode bits that contain the standard Unix permissions for this file. Read more
Sets the underlying raw bits for this set of permissions. Read more
Creates a new instance of Permissions from the given set of Unix permission bits. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.