Crate std [−] [src]
The Rust Standard Library
The Rust Standard Library is the foundation of portable Rust software, a
set of minimal and battle-tested shared abstractions for the broader Rust
ecosystem. It offers core types, like Vec<T>
and
Option<T>
, library-defined operations on language
primitives, standard macros, I/O and
multithreading, among many other things.
std
is available to all Rust crates by default, just as if each one
contained an extern crate std;
import at the crate root. Therefore the
standard library can be accessed in use
statements through the path
std
, as in use std::env
, or in expressions through the absolute path
::std
, as in ::std::env::args()
.
How to read this documentation
If you already know the name of what you are looking for, the fastest way to find it is to use the search bar at the top of the page.
Otherwise, you may want to jump to one of these useful sections:
If this is your first time, the documentation for the standard library is written to be casually perused. Clicking on interesting things should generally lead you to interesting places. Still, there are important bits you don't want to miss, so read on for a tour of the standard library and its documentation!
Once you are familiar with the contents of the standard library you may begin to find the verbosity of the prose distracting. At this stage in your development you may want to press the [-] button near the top of the page to collapse it into a more skimmable view.
While you are looking at that [-] button also notice the [src] button. Rust's API documentation comes with the source code and you are encouraged to read it. The standard library source is generally high quality and a peek behind the curtains is often enlightening.
What is in the standard library documentation?
First of all, The Rust Standard Library is divided into a number of focused
modules, all listed further down this page. These modules are
the bedrock upon which all of Rust is forged, and they have mighty names
like std::slice
and std::cmp
. Modules' documentation typically
includes an overview of the module along with examples, and are a smart
place to start familiarizing yourself with the library.
Second, implicit methods on primitive types are documented here. This can be a source of confusion for two reasons:
- While primitives are implemented by the compiler, the standard library implements methods directly on the primitive types (and it is the only library that does so), which are documented in the section on primitives.
- The standard library exports many modules with the same name as primitive types. These define additional items related to the primitive type, but not the all-important methods.
So for example there is a page for the primitive type
i32
that lists all the methods that can be called on
32-bit integers (very useful), and there is a page for the module
std::i32
that documents the constant values MIN
and
MAX
(rarely useful).
Note the documentation for the primitives str
and [T]
(also
called 'slice'). Many method calls on String
and Vec<T>
are actually
calls to methods on str
and [T]
respectively, via deref
coercions.
Third, the standard library defines The Rust Prelude, a small collection of items - mostly traits - that are imported into every module of every crate. The traits in the prelude are pervasive, making the prelude documentation a good entry point to learning about the library.
And finally, the standard library exports a number of standard macros, and lists them on this page (technically, not all of the standard macros are defined by the standard library - some are defined by the compiler - but they are documented here the same). Like the prelude, the standard macros are imported by default into all crates.
A Tour of The Rust Standard Library
The rest of this crate documentation is dedicated to pointing out notable features of The Rust Standard Library.
Containers and collections
The option
and result
modules define optional and error-handling
types, Option<T>
and Result<T, E>
. The iter
module defines
Rust's iterator trait, Iterator
, which works with the for
loop to
access collections.
The standard library exposes three common ways to deal with contiguous regions of memory:
Vec<T>
- A heap-allocated vector that is resizable at runtime.[T; n]
- An inline array with a fixed size at compile time.[T]
- A dynamically sized slice into any other kind of contiguous storage, whether heap-allocated or not.
Slices can only be handled through some kind of pointer, and as such come in many flavors such as:
&[T]
- shared slice&mut [T]
- mutable sliceBox<[T]>
- owned slice
str
, a UTF-8 string slice, is a primitive type, and the standard library
defines many methods for it. Rust str
s are typically accessed as
immutable references: &str
. Use the owned String
for building and
mutating strings.
For converting to strings use the format!
macro, and for converting from
strings use the FromStr
trait.
Data may be shared by placing it in a reference-counted box or the Rc
type, and if further contained in a Cell
or RefCell
, may be mutated
as well as shared. Likewise, in a concurrent setting it is common to pair an
atomically-reference-counted box, Arc
, with a Mutex
to get the same
effect.
The collections
module defines maps, sets, linked lists and other
typical collection types, including the common HashMap<K, V>
.
Platform abstractions and I/O
Besides basic data types, the standard library is largely concerned with abstracting over differences in common platforms, most notably Windows and Unix derivatives.
Common types of I/O, including files, TCP, UDP, are defined in the
io
, fs
, and net
modules.
The thread
module contains Rust's threading abstractions. sync
contains further primitive shared memory types, including atomic
and
mpsc
, which contains the channel types for message passing.
Primitive Types
array |
A fixed-size array, denoted |
bool |
The boolean type. |
char |
A character type. |
f32 |
The 32-bit floating point type. |
f64 |
The 64-bit floating point type. |
i16 |
The 16-bit signed integer type. |
i32 |
The 32-bit signed integer type. |
i64 |
The 64-bit signed integer type. |
i8 |
The 8-bit signed integer type. |
isize |
The pointer-sized signed integer type. |
pointer |
Raw, unsafe pointers, |
slice |
A dynamically-sized view into a contiguous sequence, |
str |
String slices. |
tuple |
A finite heterogeneous sequence, |
u16 |
The 16-bit unsigned integer type. |
u32 |
The 32-bit unsigned integer type. |
u64 |
The 64-bit unsigned integer type. |
u8 |
The 8-bit unsigned integer type. |
usize |
The pointer-sized unsigned integer type. |
Modules
any |
This module implements the |
ascii |
Operations on ASCII strings and characters. |
borrow |
A module for working with borrowed data. |
boxed |
A pointer type for heap allocation. |
cell |
Shareable mutable containers. |
char |
A character type. |
clone |
The |
cmp |
Functionality for ordering and comparison. |
collections |
Collection types. |
convert |
Traits for conversions between types. |
default |
The |
env |
Inspection and manipulation of the process's environment. |
error |
Traits for working with Errors. |
f32 |
The 32-bit floating point type. |
f64 |
The 64-bit floating point type. |
ffi |
Utilities related to FFI bindings. |
fmt |
Utilities for formatting and printing strings |
fs |
Filesystem manipulation operations. |
hash |
Generic hashing support. |
i16 |
The 16-bit signed integer type. |
i32 |
The 32-bit signed integer type. |
i64 |
The 64-bit signed integer type. |
i8 |
The 8-bit signed integer type. |
io |
Traits, helpers, and type definitions for core I/O functionality. |
isize |
The pointer-sized signed integer type. |
iter |
Composable external iteration. |
marker |
Primitive traits and marker types representing basic 'kinds' of types. |
mem |
Basic functions for dealing with memory. |
net |
Networking primitives for TCP/UDP communication. |
num |
Additional functionality for numerics. |
ops |
Overloadable operators. |
option |
Optional values. |
os |
OS-specific functionality. |
panic |
Panic support in the standard library |
path |
Cross-platform path manipulation. |
prelude |
The Rust Prelude. |
process |
Working with processes. |
ptr |
Raw, unsafe pointers, |
rc |
Thread-local reference-counted boxes (the |
result |
Error handling with the |
slice |
A dynamically-sized view into a contiguous sequence, |
str |
Unicode string slices. |
string |
A UTF-8 encoded, growable string. |
sync |
Useful synchronization primitives. |
thread |
Native threads. |
time |
Temporal quantification. |
u16 |
The 16-bit unsigned integer type. |
u32 |
The 32-bit unsigned integer type. |
u64 |
The 64-bit unsigned integer type. |
u8 |
The 8-bit unsigned integer type. |
usize |
The pointer-sized unsigned integer type. |
vec |
A contiguous growable array type with heap-allocated contents, written
|
intrinsics |
[Unstable] rustc compiler intrinsics. |
raw |
[Unstable] Contains struct definitions for the layout of compiler built-in types. |
Macros
assert! |
Ensure that a boolean expression is |
assert_eq! |
Asserts that two expressions are equal to each other. |
cfg! |
Boolean evaluation of configuration flags. |
column! |
A macro which expands to the column number on which it was invoked. |
concat! |
Concatenates literals into a static string slice. |
concat_idents! |
Concatenate identifiers into one identifier. |
debug_assert! |
Ensure that a boolean expression is |
debug_assert_eq! |
Asserts that two expressions are equal to each other. |
env! |
Inspect an environment variable at compile time. |
file! |
A macro which expands to the file name from which it was invoked. |
format! |
Use the syntax described in |
format_args! |
The core macro for formatted string creation & output. |
include! |
Parse the current given file as an expression. |
include_bytes! |
Includes a file as a reference to a byte array. |
include_str! |
Includes a utf8-encoded file as a string. |
line! |
A macro which expands to the line number on which it was invoked. |
module_path! |
Expands to a string that represents the current module path. |
option_env! |
Optionally inspect an environment variable at compile time. |
panic! |
The entry point for panic of Rust threads. |
print! |
Macro for printing to the standard output. |
println! |
Macro for printing to the standard output, with a newline. |
stringify! |
A macro which stringifies its argument. |
thread_local! |
Declare a new thread local storage key of type |
scoped_thread_local! |
[Deprecated] Declare a new scoped thread local storage key. |
select! |
[Unstable] A macro to select an event from a number of receivers. |
try! |
Helper macro for unwrapping |
unimplemented! |
A standardized placeholder for marking unfinished code. It panics with the
message |
unreachable! |
A utility macro for indicating unreachable code. |
vec! |
Creates a |
write! |
Use the |
writeln! |
Use the |