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. Therefore, the standard library can be accessed in use statements through the path std, as in use std::env.
Containers and collections
The option and result modules define optional and error-handling types, Option and Result. 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 - 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 slice
Box<[T]> - owned slice
str, a UTF-8 string slice, is a primitive type, and the standard library defines many methods for it. Rust strs 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.
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.
Re-exports
pub use core::arch;
Primitive Types:
never: Experimental The ! type, also called “never”.
array: A fixed-size array, denoted [T; N], for the element type, T, and the non-negative compile-time constant size, N.
bool: The boolean type.
char: A character type.
f32: A 32-bit floating point type (specifically, the “binary32” type defined in IEEE 754-2008).
f64: A 64-bit floating point type (specifically, the “binary64” type defined in IEEE 754-2008).
fn: Function pointers, like fn(usize) -> bool.
i8: The 8-bit signed integer type.
i16: The 16-bit signed integer type.
i32: The 32-bit signed integer type.
i64: The 64-bit signed integer type.
i128: The 128-bit signed integer type.
isize: The pointer-sized signed integer type.
pointer Raw, unsafe pointers, *const T, and *mut T.
reference References, both shared and mutable.
slice A dynamically-sized view into a contiguous sequence, [T]. Contiguous here means that elements are laid out so that every element is the same distance from its neighbors.
str: String slices.
tuple: A finite heterogeneous sequence, (T, U, ..).
u8: The 8-bit unsigned integer type.
u16: The 16-bit unsigned integer type.
u32: The 32-bit unsigned integer type.
u64: The 64-bit unsigned integer type.
u128: The 128-bit unsigned integer type.
unit: The () type, also called “unit”.
usize: The pointer-sized unsigned integer type.
------------Modules------------
assert_matches [Experimental]: Unstable module containing the unstable assert_matches macro.
backtrace[Experimental]: Support for capturing a stack backtrace of an OS thread
intrinsics[Experimental]: Compiler intrinsics.
lazy[Experimental]: Lazy values and one-time initialization of static data.
stream[Experimental]: Composable asynchronous iteration.
alloc: Memory allocation APIs.
any: This module implements the Any trait, which enables dynamic typing of any 'static type through runtime reflection.
array: Helper functions and types for fixed-length arrays.
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 Clone trait for types that cannot be ‘implicitly copied’.
cmp: Functionality for ordering and comparison.
collections: Collection types.
convert: Traits for conversions between types.
default: The Default trait for types which may have meaningful default values.
env: Inspection and manipulation of the process’s environment.
error: Traits for working with Errors.
f32: Constants specific to the f32 single-precision floating point type.
f64: Constants specific to the f64 double-precision floating point type.
ffi: Utilities related to FFI bindings.
fmt: Utilities for formatting and printing Strings.
fs: Filesystem manipulation operations.
future: Asynchronous values.
hash: Generic hashing support.
hint: Hints to compiler that affects how code should be emitted or optimized. Hints may be compile time or runtime.
i8[Deprecation]: planned Constants for the 8-bit signed integer type.
i16[Deprecation]: planned Constants for the 16-bit signed integer type.
i32[Deprecation]: planned Constants for the 32-bit signed integer type.
i64[Deprecation]: planned Constants for the 64-bit signed integer type.
i128[Deprecation]: planned Constants for the 128-bit signed integer type.
io: Traits, helpers, and type definitions for core I/O functionality.
isize[Deprecation]: planned Constants for the pointer-sized signed integer type.
iter: Composable external iteration.
marker Primitive traits and types representing basic properties 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.
pin: Types that pin data to its location in memory.
prelude: The Rust Prelude
primitive: This module reexports the primitive types to allow usage that is not possibly shadowed by other declared types.
process A module for working with processes.
ptr: Manually manage memory through raw pointers.
rc: Single-threaded reference-counting pointers. ‘Rc’ stands for ‘Reference Counted’.
result Error handling with the Result type.
slice A dynamically-sized view into a contiguous sequence, [T].
str: Unicode string slices.
string: A UTF-8–encoded, growable string.
sync: Useful synchronization primitives.
task: Types and Traits for working with asynchronous tasks.
thread: Native threads.
time: Temporal quantification.
u8[Deprecation]: planned Constants for the 8-bit unsigned integer type.
u16[Deprecation]: planned Constants for the 16-bit unsigned integer type.
u32[Deprecation]: planned Constants for the 32-bit unsigned integer type.
u64[Deprecation]: planned Constants for the 64-bit unsigned integer type.
u128[Deprecation]: planned Constants for the 128-bit unsigned integer type.
usize[Deprecation]: planned Constants for the pointer-sized unsigned integer type.
vec A contiguous growable array type with heap-allocated contents, written Vec<T>.
Macros
concat_idents[Experimental]: Concatenates identifiers into one identifier.
const_format_args[Experimental]: Same as format_args, but can be used in some const contexts.
is_aarch64_feature_detected[Experimental]: Prevents compilation if is_aarch64_feature_detected is used somewhere else than aarch64 targets.
is_arm_feature_detected[Experimental] Prevents compilation if is_arm_feature_detected is used somewhere else than ARM targets.
is_mips64_feature_detected[Experimental]: Prevents compilation if is_mips64_feature_detected is used somewhere else than MIPS64 targets.
is_mips_feature_detected[Experimental]: Prevents compilation if is_mips_feature_detected is used somewhere else than MIPS targets.
is_powerpc64_feature_detected[Experimental]: Prevents compilation if is_powerpc64_feature_detected is used somewhere else than PowerPC64 targets.
is_powerpc_feature_detected[Experimental]: Prevents compilation if is_powerpc_feature_detected: is used somewhere else than PowerPC targets.
llvm_asm[Deprecated][Experimental]: LLVM-style inline assembly.
log_syntax[Experimental]: Prints passed tokens into the standard output.
trace_macros[Experimental]: Enables or disables tracing functionality used for debugging other macros.
assert: Asserts that a boolean expression is true at runtime.
assert_eq: Asserts that two expressions are equal to each other (using PartialEq).
assert_ne: Asserts that two expressions are not equal to each other (using PartialEq).
cfg: Evaluates boolean combinations of configuration flags at compile-time.
column: Expands to the column number at which it was invoked.
compile_error: Causes compilation to fail with the given error message when encountered.
concat: Concatenates literals into a static string slice.
dbg: Prints and returns the value of a given expression for quick and dirty debugging.
debug_assert: Asserts that a boolean expression is true at runtime.
debug_assert_eq: Asserts that two expressions are equal to each other.
debug_assert_ne: Asserts that two expressions are not equal to each other.
env: Inspects an environment variable at compile time.
eprint: Prints to the standard error.
eprintln: Prints to the standard error, with a newline.
file: Expands to the file name in which it was invoked.
format: Creates a String using interpolation of runtime expressions.
format_args: Constructs parameters for the other string-formatting macros.
include Parses a file as an expression or an item according to the context.
include_bytes: Includes a file as a reference to a byte array.
include_str: Includes a UTF-8 encoded file as a string.
is_x86_feature_detected A macro to test at runtime whether a CPU feature is available on x86/x86-64 platforms.
line: Expands to the line number on which it was invoked.
matches Returns whether the given expression matches any of the given patterns.
module_path: Expands to a string that represents the current module path.
option_env: Optionally inspects an environment variable at compile time.
panic: Panics the current thread.
print: Prints to the standard output.
println: Prints to the standard output, with a newline.
stringify: Stringifies its arguments.
thread_local: Declare a new thread local storage key of type std::thread::LocalKey.
todo: Indicates unfinished code.
try[Deprecated]: Unwraps a result or propagates its error.
unimplemented: Indicates unimplemented code by panicking with a message of “not implemented”.
unreachable" Indicates unreachable code.
vec: Creates a Vec containing the arguments.
write: Writes formatted data into a buffer.
writeln: Write formatted data into a buffer, with a newline appended.
Keywords
SelfTy: The implementing type within a trait or impl block, or the current type within a type definition.
as Cast between types, or rename an import.
async: Return a Future instead of blocking the current thread.
await: Suspend execution until the result of a Future is ready.
break: Exit early from a loop.
const: Compile-time constants, compile-time evaluable functions, and raw pointers.
continue: Skip to the next iteration of a loop.
crate: A Rust binary or library.
dyn: dyn is a prefix of a trait object’s type.
else: What expression to evaluate when an if condition evaluates to false.
enum: A type that can be any one of several variants.
extern: Link to or import external code.
false: A value of type bool representing logical false.
fn: A function or function pointer.
for: Iteration with in, trait implementation with impl, or higher-ranked trait bounds (for<'a>).
if: Evaluate a block if a condition holds.
impl: Implement some functionality for a type.
in: Iterate over a series of values with for.
let: Bind a value to a variable.
loop: Loop indefinitely.
match: Control flow based on pattern matching.
mod: Organize code into modules.
move: Capture a closure’s environment by value.
mut: A mutable variable, reference, or pointer.
pub: Make an item visible to others.
ref: Bind by reference during pattern matching.
return: Return a value from a function.
self: The receiver of a method, or the current module.
static: A static item is a value which is valid for the entire duration of your program (a 'static lifetime).
struct: A type that is composed of other types.
super: The parent of the current module.
trait: A common interface for a group of types.
true: A value of type bool representing logical true.
type: Define an alias for an existing type.
union: The Rust equivalent of a C-style union.
unsafe: Code or interfaces whose memory safety cannot be verified by the type system.
use: Import or rename items from other crates or modules.
where: Add constraints that must be upheld to use an item.
while: Loop while a condition is upheld.
That's it.
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