github.com/prometheus/procfs v0.22.0: FS.Stat

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 pkg:golang/github.com/prometheus/procfs@v0.22.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/procfs@v0.22.0
Demonstrate these symbols/APIs:
  - procfs.FS.Stat

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:a64ee4c6f75d8458a9844971537464feb237c724f025d585aa8ae0a5d1cbbab0","contract":["procfs.NewDefaultFS() returns (FS, error) where error is nil","fs.Stat() returns (Stat, error) where error is nil and BootTime is positive","procfs.FS.Stat returns an error when reading from a proc mount missing stat","fs.Stat() parses BootTime, ProcessCreated, ContextSwitches, and CPUTotal metrics from procfs mount"],"goal":"verify pkg:golang/github.com/prometheus/procfs@v0.22.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/procfs@v0.22.0"],"schemaVersion":1,"symbols":["procfs.FS.Stat"]},"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@v0.22.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.22.0","symbols":["procfs.FS.Stat"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/prometheus/procfs v0.22.0

require golang.org/x/sys v0.47.0 // indirect

github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/prometheus/procfs v0.22.0 h1:6q9+/JL9IKAPbCmBrv9n5O5Ty3NKnciV5X7YGw0oics=
github.com/prometheus/procfs v0.22.0/go.mod h1:CvmFr/GVhIjIvWJZW3tgkODBQMRIf0EyWMQLHCHab58=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=

package main

import (
	"fmt"
	"os"

	"github.com/prometheus/procfs"
)

// ReadStat returns current system kernel and process statistics.
func ReadStat() (procfs.Stat, error) {
	fs, err := procfs.NewDefaultFS()
	if err != nil {
		return procfs.Stat{}, fmt.Errorf("procfs access failed: %w", err)
	}
	return fs.Stat()
}

func main() {
	stat, err := ReadStat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read proc stat: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("BootTime=%d ContextSwitches=%d ProcessesCreated=%d Running=%d Blocked=%d\n",
		stat.BootTime, stat.ContextSwitches, stat.ProcessCreated, stat.ProcessesRunning, stat.ProcessesBlocked)
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/prometheus/procfs@v0.22.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/procfs@v0.22.0"
  ],
  "symbols": [
    "procfs.FS.Stat"
  ]
}

package main

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

	"github.com/prometheus/procfs"
)

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

	// 2. Verify fs.Stat parses real /proc/stat
	stat, err := fs.Stat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Stat failed: %v\n", err)
		os.Exit(1)
	}
	if stat.BootTime == 0 {
		fmt.Fprintf(os.Stderr, "expected positive BootTime, got: %d\n", stat.BootTime)
		os.Exit(1)
	}

	// 3. Verify fs.Stat fails when stat file is missing
	tmpDir, err := os.MkdirTemp("", "proctest*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "os.MkdirTemp failed: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

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

	_, err = mockFS.Stat()
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected error when stat file is missing, got nil\n")
		os.Exit(1)
	}

	// 4. Verify mock stat parsing of BootTime, ProcessCreated, and CPUTotal
	mockContent := []byte("cpu  100 20 30 500 10 0 5 2 0 0\n" +
		"cpu0 50 10 15 250 5 0 2 1 0 0\n" +
		"cpu1 50 10 15 250 5 0 3 1 0 0\n" +
		"intr 1000 0 10\n" +
		"ctxt 5000\n" +
		"btime 1700000000\n" +
		"processes 4200\n" +
		"procs_running 2\n" +
		"procs_blocked 1\n")
	if err := os.WriteFile(filepath.Join(tmpDir, "stat"), mockContent, 0644); err != nil {
		fmt.Fprintf(os.Stderr, "os.WriteFile failed: %v\n", err)
		os.Exit(1)
	}

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

	if parsedStat.BootTime != 1700000000 {
		fmt.Fprintf(os.Stderr, "expected BootTime 1700000000, got: %d\n", parsedStat.BootTime)
		os.Exit(1)
	}
	if parsedStat.ProcessCreated != 4200 {
		fmt.Fprintf(os.Stderr, "expected ProcessCreated 4200, got: %d\n", parsedStat.ProcessCreated)
		os.Exit(1)
	}
	if parsedStat.ProcessesRunning != 2 {
		fmt.Fprintf(os.Stderr, "expected ProcessesRunning 2, got: %d\n", parsedStat.ProcessesRunning)
		os.Exit(1)
	}
	if parsedStat.ProcessesBlocked != 1 {
		fmt.Fprintf(os.Stderr, "expected ProcessesBlocked 1, got: %d\n", parsedStat.ProcessesBlocked)
		os.Exit(1)
	}
	if parsedStat.ContextSwitches != 5000 {
		fmt.Fprintf(os.Stderr, "expected ContextSwitches 5000, got: %d\n", parsedStat.ContextSwitches)
		os.Exit(1)
	}
	if parsedStat.CPUTotal.User != 1.0 || parsedStat.CPUTotal.Idle != 5.0 {
		// note: procfs converts USER_HZ (100) to seconds (float64) so 100 jiffies = 1.0s, 500 jiffies = 5.0s
		fmt.Fprintf(os.Stderr, "unexpected CPUTotal: %+v\n", parsedStat.CPUTotal)
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}