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//! # 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][crates.io]. It offers core types, like [`Vec<T>`] and //! [`Option<T>`], library-defined [operations on language //! primitives](#primitives), [standard macros](#macros), [I/O] and //! [multithreading], among [many other things][other]. //! //! `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`]. //! //! # 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 <a href="#" onclick="focusSearchBar();">search //! bar</a> at the top of the page. //! //! Otherwise, you may want to jump to one of these useful sections: //! //! * [`std::*` modules](#modules) //! * [Primitive types](#primitives) //! * [Standard macros](#macros) //! * [The Rust Prelude](prelude/index.html) //! //! 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](#modules). 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: //! //! 1. 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](#primitives). //! 2. 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`](primitive.i32.html) 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`](i32/index.html) that documents the constant values [`MIN`] and //! [`MAX`](i32/constant.MAX.html) (rarely useful). //! //! Note the documentation for the primitives [`str`] and [`[T]`][slice] (also //! called 'slice'). Many method calls on [`String`] and [`Vec<T>`] are actually //! calls to methods on [`str`] and [`[T]`][slice] respectively, via [deref //! coercions][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](#macros) (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. //! //! # Contributing changes to the documentation //! //! Check out the rust contribution guidelines [here]( //! https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md). //! The source for this documentation can be found on [Github](https://github.com/rust-lang). //! To contribute changes, make sure you read the guidelines first, then submit //! pull-requests for your suggested changes. //! //! Contributions are appreciated! If you see a part of the docs that can be //! improved, submit a PR, or chat with us first on irc.mozilla.org #rust-docs. //! //! # 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]`][array] - An inline *array* with a fixed size at compile time. //! * [`[T]`][slice] - 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] - *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. //! //! [I/O]: io/index.html //! [`MIN`]: i32/constant.MIN.html //! [TCP]: net/struct.TcpStream.html //! [The Rust Prelude]: prelude/index.html //! [UDP]: net/struct.UdpSocket.html //! [`Arc`]: sync/struct.Arc.html //! [owned slice]: boxed/index.html //! [`Cell`]: cell/struct.Cell.html //! [`FromStr`]: str/trait.FromStr.html //! [`HashMap<K, V>`]: collections/struct.HashMap.html //! [`Iterator`]: iter/trait.Iterator.html //! [`Mutex`]: sync/struct.Mutex.html //! [`Option<T>`]: option/enum.Option.html //! [`Rc`]: rc/index.html //! [`RefCell`]: cell/struct.RefCell.html //! [`Result<T, E>`]: result/enum.Result.html //! [`String`]: string/struct.String.html //! [`Vec<T>`]: vec/index.html //! [array]: primitive.array.html //! [slice]: primitive.slice.html //! [`atomic`]: sync/atomic/index.html //! [`collections`]: collections/index.html //! [`for`]: ../book/ch03-05-control-flow.html#looping-through-a-collection-with-for //! [`format!`]: macro.format.html //! [`fs`]: fs/index.html //! [`io`]: io/index.html //! [`iter`]: iter/index.html //! [`mpsc`]: sync/mpsc/index.html //! [`net`]: net/index.html //! [`option`]: option/index.html //! [`result`]: result/index.html //! [`std::cmp`]: cmp/index.html //! [`std::slice`]: slice/index.html //! [`str`]: primitive.str.html //! [`sync`]: sync/index.html //! [`thread`]: thread/index.html //! [`use std::env`]: env/index.html //! [`use`]: ../book/ch07-02-defining-modules-to-control-scope-and-privacy.html //! [crates.io]: https://crates.io //! [deref-coercions]: ../book/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods //! [files]: fs/struct.File.html //! [multithreading]: thread/index.html //! [other]: #what-is-in-the-standard-library-documentation //! [primitive types]: ../book/ch03-02-data-types.html #![stable(feature = "rust1", since = "1.0.0")] #![doc(html_root_url = "https://doc.rust-lang.org/nightly/", html_playground_url = "https://play.rust-lang.org/", issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/", test(no_crate_inject, attr(deny(warnings))), test(attr(allow(dead_code, deprecated, unused_variables, unused_mut))))] // Don't link to std. We are std. #![no_std] #![warn(deprecated_in_future)] #![warn(missing_docs)] #![warn(missing_debug_implementations)] #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings #![allow(explicit_outlives_requirements)] #![allow(unused_lifetimes)] // Tell the compiler to link to either panic_abort or panic_unwind #![needs_panic_runtime] // std may use features in a platform-specific way #![allow(unused_features)] #![cfg_attr(test, feature(print_internals, set_stdio, update_panic_count))] #![cfg_attr(all(target_vendor = "fortanix", target_env = "sgx"), feature(slice_index_methods, decl_macro, coerce_unsized, sgx_platform, ptr_wrapping_offset_from))] #![cfg_attr(all(test, target_vendor = "fortanix", target_env = "sgx"), feature(fixed_size_array, maybe_uninit_extra))] // std is implemented with unstable features, many of which are internal // compiler details that will never be stable // NB: the following list is sorted to minimize merge conflicts. #![feature(alloc_error_handler)] #![feature(alloc_layout_extra)] #![feature(allocator_api)] #![feature(allocator_internals)] #![feature(allow_internal_unsafe)] #![feature(allow_internal_unstable)] #![feature(arbitrary_self_types)] #![feature(array_error_internals)] #![feature(asm)] #![feature(associated_type_bounds)] #![cfg_attr(bootstrap, feature(bind_by_move_pattern_guards))] #![feature(box_syntax)] #![feature(c_variadic)] #![feature(cfg_target_has_atomic)] #![feature(cfg_target_thread_local)] #![feature(char_error_internals)] #![feature(clamp)] #![feature(compiler_builtins_lib)] #![feature(concat_idents)] #![feature(const_cstr_unchecked)] #![feature(const_raw_ptr_deref)] #![feature(container_error_extra)] #![feature(core_intrinsics)] #![feature(custom_test_frameworks)] #![feature(doc_alias)] #![feature(doc_cfg)] #![feature(doc_keyword)] #![feature(doc_masked)] #![feature(doc_spotlight)] #![feature(dropck_eyepatch)] #![feature(duration_constants)] #![feature(exact_size_is_empty)] #![feature(exhaustive_patterns)] #![feature(external_doc)] #![feature(fn_traits)] #![feature(format_args_nl)] #![feature(generator_trait)] #![feature(global_asm)] #![feature(hash_raw_entry)] #![feature(hashmap_internals)] #![feature(int_error_internals)] #![feature(int_error_matching)] #![feature(integer_atomics)] #![feature(lang_items)] #![feature(libc)] #![feature(link_args)] #![feature(linkage)] #![feature(log_syntax)] #![feature(maybe_uninit_ref)] #![feature(maybe_uninit_slice)] #![feature(mem_take)] #![feature(needs_panic_runtime)] #![feature(never_type)] #![feature(nll)] #![feature(non_exhaustive)] #![feature(on_unimplemented)] #![feature(optin_builtin_traits)] #![feature(panic_info_message)] #![feature(panic_internals)] #![feature(panic_unwind)] #![feature(prelude_import)] #![feature(ptr_internals)] #![feature(raw)] #![feature(renamed_spin_loop)] #![feature(rustc_attrs)] #![feature(rustc_const_unstable)] #![feature(rustc_private)] #![feature(shrink_to)] #![feature(slice_concat_ext)] #![feature(slice_internals)] #![feature(slice_patterns)] #![feature(staged_api)] #![feature(std_internals)] #![feature(stdsimd)] #![feature(stmt_expr_attributes)] #![feature(str_internals)] #![feature(test)] #![feature(thread_local)] #![feature(todo_macro)] #![feature(toowned_clone_into)] #![feature(trace_macros)] #![feature(try_reserve)] #![feature(unboxed_closures)] #![feature(untagged_unions)] #![feature(unwind_attributes)] // NB: the above list is sorted to minimize merge conflicts. #![default_lib_allocator] // Explicitly import the prelude. The compiler uses this same unstable attribute // to import the prelude implicitly when building crates that depend on std. #[prelude_import] #[allow(unused)] use prelude::v1::*; // Access to Bencher, etc. #[cfg(test)] extern crate test; #[allow(unused_imports)] // macros from `alloc` are not used on all platforms #[macro_use] extern crate alloc as alloc_crate; #[doc(masked)] #[allow(unused_extern_crates)] extern crate libc; // We always need an unwinder currently for backtraces #[doc(masked)] #[allow(unused_extern_crates)] extern crate unwind; // Only needed for now for the `std_detect` module until that crate changes to // use `cfg_if::cfg_if!` #[macro_use] #[cfg(not(test))] extern crate cfg_if; // During testing, this crate is not actually the "real" std library, but rather // it links to the real std library, which was compiled from this same source // code. So any lang items std defines are conditionally excluded (or else they // would generate duplicate lang item errors), and any globals it defines are // _not_ the globals used by "real" std. So this import, defined only during // testing gives test-std access to real-std lang items and globals. See #2912 #[cfg(test)] extern crate std as realstd; // The standard macros that are not built-in to the compiler. #[macro_use] mod macros; // The Rust prelude pub mod prelude; // Public module declarations and re-exports #[stable(feature = "rust1", since = "1.0.0")] pub use core::any; #[stable(feature = "simd_arch", since = "1.27.0")] #[doc(no_inline)] pub use core::arch; #[stable(feature = "rust1", since = "1.0.0")] pub use core::cell; #[stable(feature = "rust1", since = "1.0.0")] pub use core::clone; #[stable(feature = "rust1", since = "1.0.0")] pub use core::cmp; #[stable(feature = "rust1", since = "1.0.0")] pub use core::convert; #[stable(feature = "rust1", since = "1.0.0")] pub use core::default; #[stable(feature = "rust1", since = "1.0.0")] pub use core::hash; #[stable(feature = "rust1", since = "1.0.0")] pub use core::intrinsics; #[stable(feature = "rust1", since = "1.0.0")] pub use core::iter; #[stable(feature = "rust1", since = "1.0.0")] pub use core::marker; #[stable(feature = "rust1", since = "1.0.0")] pub use core::mem; #[stable(feature = "rust1", since = "1.0.0")] pub use core::ops; #[stable(feature = "rust1", since = "1.0.0")] pub use core::ptr; #[stable(feature = "rust1", since = "1.0.0")] pub use core::raw; #[stable(feature = "rust1", since = "1.0.0")] pub use core::result; #[stable(feature = "rust1", since = "1.0.0")] pub use core::option; #[stable(feature = "rust1", since = "1.0.0")] pub use core::isize; #[stable(feature = "rust1", since = "1.0.0")] pub use core::i8; #[stable(feature = "rust1", since = "1.0.0")] pub use core::i16; #[stable(feature = "rust1", since = "1.0.0")] pub use core::i32; #[stable(feature = "rust1", since = "1.0.0")] pub use core::i64; #[stable(feature = "i128", since = "1.26.0")] pub use core::i128; #[stable(feature = "rust1", since = "1.0.0")] pub use core::usize; #[stable(feature = "rust1", since = "1.0.0")] pub use core::u8; #[stable(feature = "rust1", since = "1.0.0")] pub use core::u16; #[stable(feature = "rust1", since = "1.0.0")] pub use core::u32; #[stable(feature = "rust1", since = "1.0.0")] pub use core::u64; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::boxed; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::rc; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::borrow; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::fmt; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::format; #[stable(feature = "pin", since = "1.33.0")] pub use core::pin; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::slice; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::str; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::string; #[stable(feature = "rust1", since = "1.0.0")] pub use alloc_crate::vec; #[stable(feature = "rust1", since = "1.0.0")] pub use core::char; #[stable(feature = "i128", since = "1.26.0")] pub use core::u128; #[stable(feature = "core_hint", since = "1.27.0")] pub use core::hint; #[stable(feature = "core_array", since = "1.36.0")] pub use core::array; pub mod f32; pub mod f64; #[macro_use] pub mod thread; pub mod ascii; pub mod backtrace; pub mod collections; pub mod env; pub mod error; pub mod ffi; pub mod fs; pub mod io; pub mod net; pub mod num; pub mod os; pub mod panic; pub mod path; pub mod process; pub mod sync; pub mod time; #[stable(feature = "futures_api", since = "1.36.0")] pub mod task { //! Types and Traits for working with asynchronous tasks. #[doc(inline)] #[stable(feature = "futures_api", since = "1.36.0")] pub use core::task::*; } #[stable(feature = "futures_api", since = "1.36.0")] pub mod future; // Platform-abstraction modules #[macro_use] mod sys_common; mod sys; pub mod alloc; // Private support modules mod panicking; mod memchr; // The runtime entry point and a few unstable public functions used by the // compiler pub mod rt; // Pull in the `std_detect` crate directly into libstd. The contents of // `std_detect` are in a different repository: rust-lang/stdarch. // // `std_detect` depends on libstd, but the contents of this module are // set up in such a way that directly pulling it here works such that the // crate uses the this crate as its libstd. #[path = "../stdarch/crates/std_detect/src/mod.rs"] #[allow(missing_debug_implementations, missing_docs, dead_code)] #[unstable(feature = "stdsimd", issue = "48556")] #[cfg(not(test))] mod std_detect; #[doc(hidden)] #[unstable(feature = "stdsimd", issue = "48556")] #[cfg(not(test))] pub use std_detect::detect; // Re-export macros defined in libcore. #[stable(feature = "rust1", since = "1.0.0")] #[allow(deprecated, deprecated_in_future)] pub use core::{ // Stable assert_eq, assert_ne, debug_assert_eq, debug_assert_ne, debug_assert, r#try, unimplemented, unreachable, write, writeln, // Unstable todo, }; // Re-export built-in macros defined through libcore. #[stable(feature = "builtin_macro_prelude", since = "1.38.0")] pub use core::{ // Stable assert, cfg, column, compile_error, concat, env, file, format_args, include, include_bytes, include_str, line, module_path, option_env, stringify, // Unstable asm, concat_idents, format_args_nl, global_asm, log_syntax, trace_macros, }; // Include a number of private modules that exist solely to provide // the rustdoc documentation for primitive types. Using `include!` // because rustdoc only looks for these modules at the crate level. include!("primitive_docs.rs"); // Include a number of private modules that exist solely to provide // the rustdoc documentation for the existing keywords. Using `include!` // because rustdoc only looks for these modules at the crate level. include!("keyword_docs.rs");