github.com/prometheus/procfs v0.6.0: FS.Meminfo

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/prometheus/procfs.FS.Meminfo in pkg:golang/github.com/prometheus/procfs@v0.6.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/procfs@v0.6.0
Demonstrate these symbols/APIs:
  - github.com/prometheus/procfs.FS.Meminfo
Required runtime conditions:
  - ecosystem: golang
  - language: go
  - packageManager: go@1.26.6
  - runtime: go@1.26.6

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:82ac1204200616fe91140eb724d8b32bde8c21d9a057e9a5ad87bd2672cba7a7","contract":["procfs.NewDefaultFS() initializes an FS instance for the default proc mount","FS.Meminfo() parses system memory statistics","Meminfo.MemTotal is non-nil and positive","Meminfo.MemFree is non-nil","FS.Meminfo() parses custom meminfo fields from mock procfs directory","FS.Meminfo() returns an error when meminfo file is missing"],"goal":"verify github.com/prometheus/procfs.FS.Meminfo in pkg:golang/github.com/prometheus/procfs@v0.6.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/procfs@v0.6.0"],"schemaVersion":1,"symbols":["github.com/prometheus/procfs.FS.Meminfo"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/procfs@v0.6.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.6.0","symbols":["github.com/prometheus/procfs.FS.Meminfo"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/prometheus/procfs v0.6.0

require golang.org/x/sys v0.0.0-20210124154548-22da62e12c0c // indirect

github.com/google/go-cmp v0.5.4 h1:L8R9j+yAqZuZjsqh/z+F1NCffTKKLShY6zXTItVIZ8M=
github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/prometheus/procfs v0.6.0 h1:mxy4L2jP6qMonqmq+aTtOx1ifVWUgG/TAmntgbh3xv4=
github.com/prometheus/procfs v0.6.0/go.mod h1:cz+aTbrPOrUb4q7XlbU9ygM+/jj0fzG6c1xBZuNvfVA=
golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20210124154548-22da62e12c0c h1:VwygUrnw9jn88c4u8GD3rZQbqrP/tgas88tPUbBxQrk=
golang.org/x/sys v0.0.0-20210124154548-22da62e12c0c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

package main

import (
	"fmt"
	"os"

	"github.com/prometheus/procfs"
)

func main() {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to initialize default procfs: %v\n", err)
		os.Exit(1)
	}

	meminfo, err := fs.Meminfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read meminfo: %v\n", err)
		os.Exit(1)
	}

	if meminfo.MemTotal != nil {
		fmt.Printf("Total Memory: %d kB\n", *meminfo.MemTotal)
	}
	if meminfo.MemFree != nil {
		fmt.Printf("Free Memory: %d kB\n", *meminfo.MemFree)
	}
	if meminfo.MemAvailable != nil {
		fmt.Printf("Available Memory: %d kB\n", *meminfo.MemAvailable)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/procfs.FS.Meminfo in pkg:golang/github.com/prometheus/procfs@v0.6.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/procfs@v0.6.0"
  ],
  "symbols": [
    "github.com/prometheus/procfs.FS.Meminfo"
  ],
  "runtimeConditions": {
    "ecosystem": "golang",
    "language": "go",
    "packageManager": "go@1.26.6",
    "runtime": "go@1.26.6"
  }
}

package main

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/prometheus/procfs"
)

func main() {
	// 1. procfs.NewDefaultFS() initializes an FS instance for the default proc mount
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewDefaultFS() failed: %v\n", err)
		os.Exit(1)
	}

	// 2. FS.Meminfo() parses system memory statistics
	meminfo, err := fs.Meminfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Meminfo() failed: %v\n", err)
		os.Exit(1)
	}

	// 3. Meminfo.MemTotal is non-nil and positive
	if meminfo.MemTotal == nil || *meminfo.MemTotal == 0 {
		fmt.Fprintf(os.Stderr, "expected positive MemTotal, got %v\n", meminfo.MemTotal)
		os.Exit(1)
	}

	// 4. Meminfo.MemFree is non-nil
	if meminfo.MemFree == nil {
		fmt.Fprintf(os.Stderr, "expected non-nil MemFree\n")
		os.Exit(1)
	}

	// 5. FS.Meminfo() parses custom meminfo fields from mock procfs directory
	mockDir, err := os.MkdirTemp("", "mock-procfs-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create mock directory: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(mockDir)

	mockData := "MemTotal:       32768 kB\nMemFree:        16384 kB\nMemAvailable:   24576 kB\nBuffers:         1024 kB\nCached:          4096 kB\n"
	if err := os.WriteFile(filepath.Join(mockDir, "meminfo"), []byte(mockData), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write mock meminfo: %v\n", err)
		os.Exit(1)
	}

	mockFS, err := procfs.NewFS(mockDir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewFS(mockDir) failed: %v\n", err)
		os.Exit(1)
	}

	mockMeminfo, err := mockFS.Meminfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "mockFS.Meminfo() failed: %v\n", err)
		os.Exit(1)
	}

	if mockMeminfo.MemTotal == nil || *mockMeminfo.MemTotal != 32768 {
		fmt.Fprintf(os.Stderr, "expected MemTotal 32768, got %v\n", mockMeminfo.MemTotal)
		os.Exit(1)
	}
	if mockMeminfo.MemFree == nil || *mockMeminfo.MemFree != 16384 {
		fmt.Fprintf(os.Stderr, "expected MemFree 16384, got %v\n", mockMeminfo.MemFree)
		os.Exit(1)
	}
	if mockMeminfo.MemAvailable == nil || *mockMeminfo.MemAvailable != 24576 {
		fmt.Fprintf(os.Stderr, "expected MemAvailable 24576, got %v\n", mockMeminfo.MemAvailable)
		os.Exit(1)
	}

	// 6. FS.Meminfo() returns an error when meminfo file is missing
	emptyDir, err := os.MkdirTemp("", "mock-empty-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create empty dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(emptyDir)

	emptyFS, err := procfs.NewFS(emptyDir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewFS(emptyDir) failed: %v\n", err)
		os.Exit(1)
	}

	if _, err := emptyFS.Meminfo(); err == nil {
		fmt.Fprintf(os.Stderr, "expected error for missing meminfo, got nil\n")
		os.Exit(1)
	}

	fmt.Println("All meminfo contracts verified successfully.")
}