OsStr & OsString - rust-course

Operating systems use their own string encoding that they use for file system paths. This means that the Rust strings cannot be used directly with operating systems. Here are the differences between Rust and the main operating systems:

Rust’s strings are UTF-8 and may contain NULL characters.
Unix’s strings are NULL terminated byte strings interpreted as UTF-8 in many cases.
Windows’ strings are NULL terminated 16-bit strings interpreted as UTF-16 in many cases.

OsStr and OsString (part of the std::ffi module) allow to make the transition between Rust’s strings and the operating system:

OsString stores its string on the heap.
OsStr is a slice on an operating system’s string.

See Table 1 and Table 2 for lists of the most useful methods for these both types.

Table 1:Some methods of OsStr

Method	Description
`display()`	Returns an object that represent the current string and can be safely printed, eliminating non-Unicode characters.
`is_ascii()`	Returns `true` if all characters are ASCII.
`is_empty()`	Returns `true` if the string is empty.
`len()`	Returns the string’s length.
`new(s)`	Creates a new `OsStr` slice from a string slice.
`make_ascii_lowercase()`	Puts ASCII characters in lowercase.
`make_ascii_uppercase()`	Puts ASCII characters in uppercase.
`to_ascii_lowercase()`	Returns an `OsString` with ASCII characters in lowercase.
`to_ascii_uppercase()`	Returns an `OsString` with ASCII characters in uppercase.
`to_os_string()`	Returns a copy of this string as an `OsString`.
`to_str()`	Returns a string slice of this string is a valid UTF-8 string, otherwise returns `None`.
`to_string_lossy()`	Converts this string into a UTF-8 string, replacing non-UTF-8 characters by the Unicode `U+FFFD REPLACEMENT CHARACTER` (�).

Table 2:Some methods of OsString

Method	Description
`as_os_str()`	Converts to an `OsStr` slice.
`clear()`	Removes all content.
`into_boxed_os_str()`	Converts into a `Box<OsStr>`.
`into_encoded_bytes()`	Converts into a `Vec<u8>`.
`into_string()`	Converts into a `String` or returns the original `OsString` through the error value.
`leak()`	Consumes the internal string and returns it as a `&'a mut OsStr`.
`push(s)`	Appends a string to this `OsString`.

use std::ffi::OsString;

OsString::from("foo.txt")

"foo.txt"

use std::ffi::OsString;

let s: OsString = "foo.txt".into();
s

"foo.txt"

use std::ffi::OsString;

let mut s = OsString::new();
s.push("abc/def.txt");
s

Couldn't automatically determine type of variable `s`.
Please give it an explicit type.

36.1 OsStr & OsString