`std/os`

What a program asks about the machine it runs on (docs/design/OS.md): the environment it was started with, which system and version it is, and where the user's files belong. The three target constants of std/core are re-exported, so that a file that branches on the system writes one import.

Environment and EnvironmentVariables - read one variable, list them all, split the search path.
System and SystemVersion - the version, the host name, the uptime, the page size, the machine's architecture.
Memory and Swap - how much memory the machine has, how much of it is available, and its swap.
Processor, ProcessorTimes and ProcessorUsage - how many processors the machine has, the time they have spent in each state, and how busy they were over an interval; ProcessorDescription is what a processor says about itself, Frequency a processor clock, ProcessorCache one of its caches and ProcessorFeature an instruction-set extension it offers.
CurrentProcess and ProcessResources - this process's identifier and its parent's, its executable, working directory and uptime, the processor time and memory it uses, its processors and its memory limit.
Volume, VolumeKind and VolumeSpace - the mounted file systems, what kind of storage each is, and how full.
Directories - home, configuration, data, state, cache and temporary files, by the convention of the system.
User - the account this process runs as: its name, full name, identifier, home directory and whether it is elevated.
Entropy - bytes of the system's source of randomness, for keys, nonces and the seed of a generator.
NetworkInterface, InterfaceAddress, InterfaceStatus and InterfaceKind - the machine's network interfaces, their addresses with the length of their prefix, whether the link is up and what kind of interface each is.
MacAddress - the hardware address of a network interface, read from and shown as text; it reads nothing from the machine.
OsError - what every question that can fail fails with.

A branch on the system is a match OperatingSystem.current: every arm is type checked on every machine, and only the arm of the build's target is compiled. Each module above is such a branch, and each arm hands its question to a directory of its own - windows/, linux/, macos/, freebsd/, browser/ for one system, posix/, bsd/, xdg/ for a standard several share. Those directories hold the raw natives (browser/ has none: a page asks the machine nothing); torb check --every-target reports one that is reached on a system it does not exist on.

Modules

std/os/directories[Directories]: where a user's files belong by the convention of the system - the home directory, and the bases for configuration, data, state, cache and temporary files.
std/os/entropy[Entropy]: bytes of the operating system's source of randomness, which is fit for cryptography - what a key, a nonce, a token and the seed of a generator are made from (docs/design/RANDOM.md).
std/os/environmentThe environment this process was started with: [Environment] reads one variable, lists every one as a value, and splits the search path; [EnvironmentVariables] is that list as a value a program can change and hand on.
std/os/error[OsError], what asking the operating system can go wrong with, and [outcome], the one function that turns the answer of a native of runtime/os/ into a Result.
std/os/macaddress[MacAddress]: the hardware address of a network interface, as a value like any other (docs/design/OS.md section 5.5).
std/os/memory[Memory] - how much memory the machine has and how much of it a new allocation could still get - and [Swap], the space on disk the system pages memory out to.
std/os/network[NetworkInterface] - a network interface of the machine with its addresses - and the values it is made of: [InterfaceAddress], [InterfaceStatus] and [InterfaceKind].
std/os/process[CurrentProcess] - what the operating system knows about this process: its identifier and its parent's, the executable it runs, its working directory, how long it has been running, and the resources it uses and may use ([ProcessResources], its processors, its memory limit).
std/os/processor[Processor] - how many processors the machine has, what they are and how busy they are - with [ProcessorTimes], the cumulative time each state has taken, [ProcessorUsage], the fractions of an interval, [ProcessorDescription], what a processor says about itself, and [Frequency], a processor clock.
std/os/system[System] - which operating system this is and which version, the host name, how long it has been running, the size of a memory page and the architecture of the machine - and [SystemVersion], the name and version it answers.
std/os/user[User] - the account this process runs as.
std/os/volumes[Volume] - a mounted file system - with its [VolumeKind] and, in step with [Volume.space], its [VolumeSpace].

Everything

type CurrentProcessWhat the operating system knows about this process.
type DirectoriesWhere a user's files belong, by the convention of the system.
type EntropyThe operating system's source of randomness: BCryptGenRandom on Windows, getrandom on Linux and FreeBSD, getentropy on macOS, and crypto.getRandomValues in the browser.
type EnvironmentThe environment this process was started with: read, listed, and handed on as a value.
type EnvironmentVariablesA set of environment variables as a value.
type FrequencyA processor clock: a count of hertz.
type InterfaceAddressOne address of an interface, with the length of its network prefix: 192.168.1.23/24, fe80::1/64.
type InterfaceKindWhat kind of interface a [NetworkInterface] is.
type InterfaceStatusWhether the link of an interface is up.
type MacAddressA MAC address: six octets, held as one number of 48 bits.
type MemoryHow much memory the machine has, and how much of it a new allocation could still get without swapping.
type NetworkInterfaceA network interface and its addresses.
type OsErrorWhat asking the operating system went wrong with.
type ProcessorThe processors of this machine.
type ProcessorCacheOne cache of a processor, as the processor describes it: the level, what it holds, how large it is and how long its lines are.
type ProcessorDescriptionWhat a processor says about itself, as [Processor.describe] reads it.
type ProcessorFeatureAn instruction-set extension a program may dispatch on, named after the extension as its vendor spells it.
type ProcessorTimesCumulative time in each state.
type ProcessorUsageFractions of an interval, each between 0 and 1.
type ProcessResourcesWhat the current process has used, from [CurrentProcess.resources]: getrusage on Linux and macOS with the resident size each reads its own way, GetProcessTimes and GetProcessMemoryInfo on Windows.
type SwapThe swap of the machine: the page files on Windows, the swap partitions and files on Linux, the swap files macOS makes as it needs them.
type SystemWhich system this is, which version, and how long it has been running.
type SystemVersionThe name and version of the running system.
type UserThe account this process runs as: who it is for the system, what people call it, and where its files are.
type VolumeA mounted file system: where it is mounted, what is mounted there, and what kind of storage it is.
type VolumeKindWhat a [Volume] is stored on.
type VolumeSpaceHow big a [Volume] is and how much of it is free.