Documentation
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Overview ¶
Package meminfo reads host memory and swap usage from the kernel and presents it as a normalised cross-platform Info struct.
This package lives under builtins/internal/ and is therefore exempt from the builtinAllowedSymbols allowlist check. It may use OS-specific APIs freely.
Sandbox bypass ¶
The Linux backend reads /proc/meminfo via os.Open directly, intentionally bypassing the AllowedPaths sandbox (callCtx.OpenFile). The path is a kernel-managed pseudo-file that is hardcoded by this package and never derived from user-supplied input, so AllowedPaths restrictions do not apply. This matches the documented exception used by the ss, ip route, and df builtins. No process- or environment-scoped data is read (no PIDs, no argv, no environ) — only aggregate, host-wide counters.
Platform support ¶
Only Linux is supported; macOS and Windows return ErrNotSupported.
macOS has no sysctl(3)-exposed equivalent of the page-level active/inactive/wired/free breakdown that GNU free reports: that data is only available through the Mach host_statistics64 RPC, which requires either cgo or dynamic libSystem symbol resolution (neither of which any existing builtin in this repo uses).
Windows' GlobalMemoryStatusEx is easy to call, but it has no equivalent of buffers/cache/shared/available in the Linux sense — reporting those columns as a literal 0 would read as "this host has no page cache" rather than "this field does not exist on this platform", which could mislead an agent's memory-pressure diagnosis. Rather than ship a half-mapped or ambiguous result, both platforms fail clearly, matching the existing "ip route" precedent for commands that read Linux-only kernel state.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ErrNotSupported = errors.New("not supported on this platform")
ErrNotSupported is returned by Read on platforms without a backend.
Functions ¶
This section is empty.
Types ¶
type Info ¶
type Info struct {
// MemTotal is total usable RAM.
MemTotal uint64
// MemFree is memory not used for anything at all (kernel or userspace).
MemFree uint64
// MemAvailable is the kernel's own estimate of memory available for
// starting new applications, without swapping (Linux ≥3.14). When the
// kernel does not report it, Read falls back to
// MemFree+Buffers+Cached, the pre-3.14 approximation.
MemAvailable uint64
// Buffers is memory in raw block-device buffers.
Buffers uint64
// Cached is page-cache memory, minus Shared.
Cached uint64
// SReclaimable is reclaimable slab memory (part of "buff/cache" in
// modern free output).
SReclaimable uint64
Shared uint64
// SwapTotal is total swap space.
SwapTotal uint64
// SwapFree is unused swap space.
SwapFree uint64
}
Info describes host memory and swap usage, in bytes. Fields map directly to the /proc/meminfo keys of the same name; only Linux is implemented (see the package doc comment for why macOS and Windows are not).
Source Files