github.com/prometheus/procfs v0.12.0: NewDefaultFS

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.NewDefaultFS in pkg:golang/github.com/prometheus/procfs@v0.12.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/procfs@v0.12.0
Demonstrate these symbols/APIs:
  - github.com/prometheus/procfs.NewDefaultFS
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:5ff86cfede32bb5e8a581284190ec72ed502334048b69872888df6475430a822","contract":["procfs.NewDefaultFS() returns (FS, error) where error is nil","fs.Meminfo() returns (*Meminfo, error) where error is nil and MemTotal is non-nil","fs.Self() returns (Proc, error) where error is nil and PID is positive","proc.Stat() returns (ProcStat, error) where error is nil, PID matches, and Comm is non-empty","fs.Stat() returns (Stat, error) where error is nil and BootTime is non-zero"],"goal":"verify github.com/prometheus/procfs.NewDefaultFS in pkg:golang/github.com/prometheus/procfs@v0.12.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/procfs@v0.12.0"],"schemaVersion":1,"symbols":["github.com/prometheus/procfs.NewDefaultFS"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/procfs@v0.12.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.12.0","symbols":["github.com/prometheus/procfs.NewDefaultFS"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/prometheus/procfs v0.12.0

require golang.org/x/sys v0.12.0 // indirect

github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
github.com/prometheus/procfs v0.12.0 h1:jluTpSng7V9hY0O2R9DzzJHYb2xULk9VTR1V1R/k6Bo=
github.com/prometheus/procfs v0.12.0/go.mod h1:pcuDEFsWDnvcgNzo4EEweacyhjeA9Zk3cnaOZAZEfOo=
golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

package main

import (
	"fmt"
	"os"

	"github.com/prometheus/procfs"
)

func ReadSystemMemory() (uint64, error) {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		return 0, err
	}
	meminfo, err := fs.Meminfo()
	if err != nil {
		return 0, err
	}
	if meminfo.MemTotal == nil {
		return 0, fmt.Errorf("memtotal not found")
	}
	return *meminfo.MemTotal, nil
}

func ReadCurrentProcessStat() (int, string, error) {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		return 0, "", err
	}
	proc, err := fs.Self()
	if err != nil {
		return 0, "", err
	}
	stat, err := proc.Stat()
	if err != nil {
		return 0, "", err
	}
	return proc.PID, stat.Comm, nil
}

func main() {
	memTotal, err := ReadSystemMemory()
	if err != nil {
		fmt.Fprintf(os.Stderr, "error reading meminfo: %v\n", err)
		os.Exit(1)
	}
	pid, comm, err := ReadCurrentProcessStat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "error reading proc stat: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("PID: %d, Comm: %s, MemTotal: %d kB\n", pid, comm, memTotal)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/procfs.NewDefaultFS in pkg:golang/github.com/prometheus/procfs@v0.12.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/procfs@v0.12.0"
  ],
  "symbols": [
    "github.com/prometheus/procfs.NewDefaultFS"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"fmt"
	"os"

	"github.com/prometheus/procfs"
)

func main() {
	// 1. procfs.NewDefaultFS() returns (FS, error) where error is nil
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewDefaultFS failed: %v\n", err)
		os.Exit(1)
	}

	// 2. fs.Meminfo() returns (*Meminfo, error) where error is nil and MemTotal is non-nil
	meminfo, err := fs.Meminfo()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Meminfo failed: %v\n", err)
		os.Exit(1)
	}
	if meminfo.MemTotal == nil || *meminfo.MemTotal == 0 {
		fmt.Fprintf(os.Stderr, "expected positive MemTotal, got %v\n", meminfo.MemTotal)
		os.Exit(1)
	}

	// 3. fs.Self() returns (Proc, error) where error is nil and PID is positive
	proc, err := fs.Self()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Self failed: %v\n", err)
		os.Exit(1)
	}
	if proc.PID <= 0 {
		fmt.Fprintf(os.Stderr, "expected positive PID, got %d\n", proc.PID)
		os.Exit(1)
	}

	// 4. proc.Stat() returns (ProcStat, error) where error is nil, PID matches, and Comm is non-empty
	stat, err := proc.Stat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "proc.Stat failed: %v\n", err)
		os.Exit(1)
	}
	if stat.PID != proc.PID {
		fmt.Fprintf(os.Stderr, "expected stat.PID %d == proc.PID %d\n", stat.PID, proc.PID)
		os.Exit(1)
	}
	if stat.Comm == "" {
		fmt.Fprintf(os.Stderr, "expected non-empty stat.Comm\n")
		os.Exit(1)
	}

	// 5. fs.Stat() returns (Stat, error) where error is nil and BootTime is non-zero
	systemStat, err := fs.Stat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Stat failed: %v\n", err)
		os.Exit(1)
	}
	if systemStat.BootTime == 0 {
		fmt.Fprintf(os.Stderr, "expected non-zero BootTime\n")
		os.Exit(1)
	}

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