pub struct OsString { /* private fields */ }Expand description
A type that can represent owned, mutable platform-native strings, but is cheaply inter-convertible with Rust strings.
The need for this type arises from the fact that:
-
On Unix systems, strings are often arbitrary sequences of non-zero bytes, in many cases interpreted as UTF-8.
-
On Windows, strings are often arbitrary sequences of non-zero 16-bit values, interpreted as UTF-16 when it is valid to do so.
-
In Rust, strings are always valid UTF-8, which may contain zeros.
OsString and OsStr bridge this gap by simultaneously representing Rust
and platform-native string values, and in particular allowing a Rust string
to be converted into an “OS” string with no cost if possible. A consequence
of this is that OsString instances are not NUL terminated; in order
to pass to e.g., Unix system call, you should create a CStr.
OsString is to &OsStr as String is to &str: the former
in each pair are owned strings; the latter are borrowed
references.
Note, OsString and OsStr internally do not necessarily hold strings in
the form native to the platform; While on Unix, strings are stored as a
sequence of 8-bit values, on Windows, where strings are 16-bit value based
as just discussed, strings are also actually stored as a sequence of 8-bit
values, encoded in a less-strict variant of UTF-8. This is useful to
understand when handling capacity and length values.
Capacity of OsString
Capacity uses units of UTF-8 bytes for OS strings which were created from valid unicode, and
uses units of bytes in an unspecified encoding for other contents. On a given target, all
OsString and OsStr values use the same units for capacity, so the following will work:
use std::ffi::{OsStr, OsString};
fn concat_os_strings(a: &OsStr, b: &OsStr) -> OsString {
let mut ret = OsString::with_capacity(a.len() + b.len()); // This will allocate
ret.push(a); // This will not allocate further
ret.push(b); // This will not allocate further
ret
}Creating an OsString
From a Rust string: OsString implements
From<String>, so you can use my_string.into() to
create an OsString from a normal Rust string.
From slices: Just like you can start with an empty Rust
String and then String::push_str some &str
sub-string slices into it, you can create an empty OsString with
the OsString::new method and then push string slices into it with the
OsString::push method.
Extracting a borrowed reference to the whole OS string
You can use the OsString::as_os_str method to get an &OsStr from
an OsString; this is effectively a borrowed reference to the
whole string.
Conversions
See the module’s toplevel documentation about conversions for a discussion on
the traits which OsString implements for conversions from/to native representations.
Implementations
sourceimpl OsString
impl OsString
sourcepub fn into_string(self) -> Result<String, OsString>
pub fn into_string(self) -> Result<String, OsString>
1.9.0 · sourcepub fn with_capacity(capacity: usize) -> OsString
pub fn with_capacity(capacity: usize) -> OsString
Creates a new OsString with at least the given capacity.
The string will be able to hold at least capacity length units of other
OS strings without reallocating. This method is allowed to allocate for
more units than capacity. If capacity is 0, the string will not
allocate.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsString;
let mut os_string = OsString::with_capacity(10);
let capacity = os_string.capacity();
// This push is done without reallocating
os_string.push("foo");
assert_eq!(capacity, os_string.capacity());1.9.0 · sourcepub fn reserve(&mut self, additional: usize)
pub fn reserve(&mut self, additional: usize)
Reserves capacity for at least additional more capacity to be inserted
in the given OsString. Does nothing if the capacity is
already sufficient.
The collection may reserve more space to speculatively avoid frequent reallocations.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsString;
let mut s = OsString::new();
s.reserve(10);
assert!(s.capacity() >= 10);1.63.0 · sourcepub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
Tries to reserve capacity for at least additional more length units
in the given OsString. The string may reserve more space to speculatively avoid
frequent reallocations. After calling try_reserve, capacity will be
greater than or equal to self.len() + additional if it returns Ok(()).
Does nothing if capacity is already sufficient. This method preserves
the contents even if an error occurs.
See the main OsString documentation information about encoding and capacity units.
Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
Examples
use std::ffi::{OsStr, OsString};
use std::collections::TryReserveError;
fn process_data(data: &str) -> Result<OsString, TryReserveError> {
let mut s = OsString::new();
// Pre-reserve the memory, exiting if we can't
s.try_reserve(OsStr::new(data).len())?;
// Now we know this can't OOM in the middle of our complex work
s.push(data);
Ok(s)
}1.9.0 · sourcepub fn reserve_exact(&mut self, additional: usize)
pub fn reserve_exact(&mut self, additional: usize)
Reserves the minimum capacity for at least additional more capacity to
be inserted in the given OsString. Does nothing if the capacity is
already sufficient.
Note that the allocator may give the collection more space than it
requests. Therefore, capacity can not be relied upon to be precisely
minimal. Prefer reserve if future insertions are expected.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsString;
let mut s = OsString::new();
s.reserve_exact(10);
assert!(s.capacity() >= 10);1.63.0 · sourcepub fn try_reserve_exact(
&mut self,
additional: usize
) -> Result<(), TryReserveError>
pub fn try_reserve_exact(
&mut self,
additional: usize
) -> Result<(), TryReserveError>
Tries to reserve the minimum capacity for at least additional
more length units in the given OsString. After calling
try_reserve_exact, capacity will be greater than or equal to
self.len() + additional if it returns Ok(()).
Does nothing if the capacity is already sufficient.
Note that the allocator may give the OsString more space than it
requests. Therefore, capacity can not be relied upon to be precisely
minimal. Prefer try_reserve if future insertions are expected.
See the main OsString documentation information about encoding and capacity units.
Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
Examples
use std::ffi::{OsStr, OsString};
use std::collections::TryReserveError;
fn process_data(data: &str) -> Result<OsString, TryReserveError> {
let mut s = OsString::new();
// Pre-reserve the memory, exiting if we can't
s.try_reserve_exact(OsStr::new(data).len())?;
// Now we know this can't OOM in the middle of our complex work
s.push(data);
Ok(s)
}1.19.0 · sourcepub fn shrink_to_fit(&mut self)
pub fn shrink_to_fit(&mut self)
Shrinks the capacity of the OsString to match its length.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsString;
let mut s = OsString::from("foo");
s.reserve(100);
assert!(s.capacity() >= 100);
s.shrink_to_fit();
assert_eq!(3, s.capacity());1.56.0 · sourcepub fn shrink_to(&mut self, min_capacity: usize)
pub fn shrink_to(&mut self, min_capacity: usize)
Shrinks the capacity of the OsString with a lower bound.
The capacity will remain at least as large as both the length and the supplied value.
If the current capacity is less than the lower limit, this is a no-op.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsString;
let mut s = OsString::from("foo");
s.reserve(100);
assert!(s.capacity() >= 100);
s.shrink_to(10);
assert!(s.capacity() >= 10);
s.shrink_to(0);
assert!(s.capacity() >= 3);1.20.0 · sourcepub fn into_boxed_os_str(self) -> Box<OsStr>ⓘNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A>where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>
pub fn into_boxed_os_str(self) -> Box<OsStr>ⓘNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A>where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>
Methods from Deref<Target = OsStr>
sourcepub fn to_string_lossy(&self) -> Cow<'_, str>
pub fn to_string_lossy(&self) -> Cow<'_, str>
Converts an OsStr to a Cow<str>.
Any non-Unicode sequences are replaced with
U+FFFD REPLACEMENT CHARACTER.
Examples
Calling to_string_lossy on an OsStr with invalid unicode:
// Note, due to differences in how Unix and Windows represent strings,
// we are forced to complicate this example, setting up example `OsStr`s
// with different source data and via different platform extensions.
// Understand that in reality you could end up with such example invalid
// sequences simply through collecting user command line arguments, for
// example.
#[cfg(unix)] {
use std::ffi::OsStr;
use std::os::unix::ffi::OsStrExt;
// Here, the values 0x66 and 0x6f correspond to 'f' and 'o'
// respectively. The value 0x80 is a lone continuation byte, invalid
// in a UTF-8 sequence.
let source = [0x66, 0x6f, 0x80, 0x6f];
let os_str = OsStr::from_bytes(&source[..]);
assert_eq!(os_str.to_string_lossy(), "fo�o");
}
#[cfg(windows)] {
use std::ffi::OsString;
use std::os::windows::prelude::*;
// Here the values 0x0066 and 0x006f correspond to 'f' and 'o'
// respectively. The value 0xD800 is a lone surrogate half, invalid
// in a UTF-16 sequence.
let source = [0x0066, 0x006f, 0xD800, 0x006f];
let os_string = OsString::from_wide(&source[..]);
let os_str = os_string.as_os_str();
assert_eq!(os_str.to_string_lossy(), "fo�o");
}sourcepub fn to_os_string(&self) -> OsString
pub fn to_os_string(&self) -> OsString
1.9.0 · sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the length of this OsStr.
Note that this does not return the number of bytes in the string in OS string form.
The length returned is that of the underlying storage used by OsStr.
As discussed in the OsString introduction, OsString and OsStr
store strings in a form best suited for cheap inter-conversion between
native-platform and Rust string forms, which may differ significantly
from both of them, including in storage size and encoding.
This number is simply useful for passing to other methods, like
OsString::with_capacity to avoid reallocations.
See the main OsString documentation information about encoding and capacity units.
Examples
use std::ffi::OsStr;
let os_str = OsStr::new("");
assert_eq!(os_str.len(), 0);
let os_str = OsStr::new("foo");
assert_eq!(os_str.len(), 3);1.53.0 · sourcepub fn make_ascii_lowercase(&mut self)
pub fn make_ascii_lowercase(&mut self)
Converts this string to its ASCII lower case equivalent in-place.
ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.
To return a new lowercased value without modifying the existing one, use
OsStr::to_ascii_lowercase.
Examples
use std::ffi::OsString;
let mut s = OsString::from("GRÜßE, JÜRGEN ❤");
s.make_ascii_lowercase();
assert_eq!("grÜße, jÜrgen ❤", s);1.53.0 · sourcepub fn make_ascii_uppercase(&mut self)
pub fn make_ascii_uppercase(&mut self)
Converts this string to its ASCII upper case equivalent in-place.
ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.
To return a new uppercased value without modifying the existing one, use
OsStr::to_ascii_uppercase.
Examples
use std::ffi::OsString;
let mut s = OsString::from("Grüße, Jürgen ❤");
s.make_ascii_uppercase();
assert_eq!("GRüßE, JüRGEN ❤", s);1.53.0 · sourcepub fn to_ascii_lowercase(&self) -> OsString
pub fn to_ascii_lowercase(&self) -> OsString
Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.
ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.
To lowercase the value in-place, use OsStr::make_ascii_lowercase.
Examples
use std::ffi::OsString;
let s = OsString::from("Grüße, Jürgen ❤");
assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());1.53.0 · sourcepub fn to_ascii_uppercase(&self) -> OsString
pub fn to_ascii_uppercase(&self) -> OsString
Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.
ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.
To uppercase the value in-place, use OsStr::make_ascii_uppercase.
Examples
use std::ffi::OsString;
let s = OsString::from("Grüße, Jürgen ❤");
assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());1.53.0 · sourcepub fn eq_ignore_ascii_case<S: AsRef<OsStr>>(&self, other: S) -> bool
pub fn eq_ignore_ascii_case<S: AsRef<OsStr>>(&self, other: S) -> bool
Checks that two strings are an ASCII case-insensitive match.
Same as to_ascii_lowercase(a) == to_ascii_lowercase(b),
but without allocating and copying temporaries.
Examples
use std::ffi::OsString;
assert!(OsString::from("Ferris").eq_ignore_ascii_case("FERRIS"));
assert!(OsString::from("Ferrös").eq_ignore_ascii_case("FERRöS"));
assert!(!OsString::from("Ferrös").eq_ignore_ascii_case("FERRÖS"));Trait Implementations
1.52.0 · sourceimpl<'a> Extend<&'a OsStr> for OsString
impl<'a> Extend<&'a OsStr> for OsString
sourcefn extend<T: IntoIterator<Item = &'a OsStr>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = &'a OsStr>>(&mut self, iter: T)
sourcefn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one #72631)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one #72631)1.52.0 · sourceimpl<'a> Extend<Cow<'a, OsStr>> for OsString
impl<'a> Extend<Cow<'a, OsStr>> for OsString
sourcefn extend<T: IntoIterator<Item = Cow<'a, OsStr>>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = Cow<'a, OsStr>>>(&mut self, iter: T)
sourcefn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one #72631)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one #72631)1.52.0 · sourceimpl Extend<OsString> for OsString
impl Extend<OsString> for OsString
sourcefn extend<T: IntoIterator<Item = OsString>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = OsString>>(&mut self, iter: T)
sourcefn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one #72631)sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one #72631)1.20.0 · sourceimpl From<OsString> for Box<OsStr>
impl From<OsString> for Box<OsStr>
sourcefn from(s: OsString) -> Box<OsStr>ⓘNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A>where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>
fn from(s: OsString) -> Box<OsStr>ⓘNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A>where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A>where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W>