In Rust lang programming the std::os::linux::fs::MetadataExt trait provides os-specific extensions for the Linux platform. These extensions allow programmers to view metadata about a file such as its permissions, size, modification times, and other information about a file. The MetadataExt trait is a part of the Linux-specific extensions to primitives in the std::fs module.

In this blog post we will cover some of the functions associated with this trait that allows programmers to supercharge their development work on the Linux operating system. In order to begin let's first import the necessary libraries.

If you’d like to access actual code for these examples you can find examples in this blog posts GitHub repo.

Importing the Rust Standard Library (std::fs)

To begin we need to import the Rust standard library (std::fs) in order to gain access to the metadata() function which will return a Metadata structure.

Importing fs::MetadataExt for Linux 

Next, we can import the MetadataExt trait for the Metadata struct for Linux.

Setting an Example File Variable

Next, assign a local file to a Rust variable using the const keyword. 

Defining a Variable to Hold Our Metadata Struct Object

After we have a local file variable, let's pass this variable to the std::fs::metadata() function. This function will store a file Metadata result object. The std::fs::metadata() function will get information about a file given a path and query the file system for us. We can then use the MetadataExt trait for Linux on this Metadata structure.

Rust File MetadataExt: Linux OS Functions & Trait Implementations Code Examples

In the following examples, we will explore the Linux OS MetadataExt trait functions and see what types of information we can gather from it.

Linux MetadataExt Rust trait: How do I get the device ID where a file resides?

To get the device ID on which the file object resides, we can pass the st_dev() function, which will return a u64 ID value.

Linux MetadataExt Rust trait: How do I get the inode number of a file?

What is an inode number? An inode number is a Linux and Unix-like data structure that keeps track of all the files and directories on the system. To get the inode value of a file object, we can pass the st_ino() function, which will return a u64 inode number.

Linux MetadataExt Rust trait: How do I get a file's file type and mode?

To return a file object's file type and mode, we can pass the st_mode() function to the Metadata object, which returns a u32 value.

Linux MetadataExt Rust trait: How do I get the hard links to a file?

To get the number of hard links to a file in Rust, we can pass the st_nlink() to the Metadata object, which returns the number of hard links as a u64 value. 

Linux MetadataExt Rust trait: How do I get the user ID of the file owner?

To return the user ID of the file owner, we can pass the st_uid() function to the file, which returns a u32 user ID value.

Linux MetadataExt Rust trait: How do I get the group ID of the file owner?

To return the group ID of the file owner, we can pass the st_gid() function to the file, which returns a u32 group ID value.

Linux MetadataExt Rust trait: How do I get the device ID of a special file?

To return the device ID of a special file object, we can pass the st_rdev() function to the Metadata object, which returns a u64 ID value.

Linux MetadataExt Rust trait: How do I get the size of a file in bytes?

To get the size of a file in bytes, we can pass the st_size() function to the Metadata object, which returns a u64 byte size value.

Linux MetadataExt Rust trait: How do I get the last access time of a file since Unix Epoch?

To get the last access time since the Unix Epoch of a file, we can pass the st_atime() function to the Metadata object, which returns a 64-bit signed integer type (i64) value.

Linux MetadataExt Rust trait: How do I get the last access time of a file in nanoseconds since Unix Epoch?

To get the last access time in nanoseconds since the Unix Epoch of a file, we can pass the st_atime_nsec() function to the Metadata object, which returns a 64-bit signed integer type (i64) value representing the last access time in nanoseconds since Unix Epoch (st_atime).

Linux MetadataExt Rust trait: How do I get the last modified time of a file since Unix Epoch?

To get the last modified time since the Unix Epoch of a file, we can pass the st_mtime() function to the Metadata object, which returns a 64-bit signed integer type (i64) value.

Linux MetadataExt Rust trait: How do I get the last modified time of a file in nanoseconds since Unix Epoch?

To get the last modified time in nanoseconds since the Unix Epoch of a file, we can pass the st_mtime_nsec() function to the Metadata object, which returns a 64-bit signed integer type (i64) value representing the last modified time in nanoseconds since Unix Epoch (st_atime).

Linux MetadataExt Rust trait: How do I get a file's last status change time since Unix Epoch?

To get the last status change time of a file in seconds, we can pass the st_ctime() function to the Metadata object, which will return an i64 value of seconds since the Unix Epoch.

Linux MetadataExt Rust trait: How do I get a file's last status change time since Unix Epoch in nanoseconds?

To get the last status change time of a file in nanoseconds, we can pass the st_ctime_nsec() function to the Metadata object, which will return an i64 value of nanoseconds since Unix Epoch (st_ctime).

Linux MetadataExt Rust trait: How to get the preferred block size for efficient IO operations?

To return the preferred block size for efficient IO operation, we can pass the st_blksize() function, which returns a u64 value.

Linux MetadataExt Rust trait: How do you get the number of blocks allocated to a file?

To get the number of blocks allocated to a file in 512-byte units, we can pass the st_block() function to the Metadata object, which returns a u64 number of blocks value.

Linux MetadataExt Rust trait: Full Code Examples

Here is a full code example of the various MetadataExt trait implementation functions available to the Linux operating system. You can also access this project through GitHub.

Looking for Metadata Extensions for MacOS & Windows?

If you’re looking for examples on the MetadataExt trait implementations for other unix-like operating systems, MacOS, and Windows you can find a comprehensive list by clicking the following button.

Rust Metadata Extensions (std::os::linux::fs::MetadataExt) for the Linux OS Conclusion

In conclusion the Metadata Extensions (std::os::linux::fs::MetadataExt) trait for the Linux operating system provides programmers with a plethora of tools to gather information about a files metadata. From gaining information on access times to information about permissions the MetadataExt trait gives developers the tools they need to interact with files on the filesystem and build rich interactive applications.

If you have any questions on implementing this trait in Linux feel free to reach out with any questions you might have!