github.com/prometheus/procfs v0.6.0: DefaultMountPoint

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.DefaultMountPoint 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.DefaultMountPoint

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:sha256:60b87412bae08d5260f21c97cdfe06c78c49b0a48081f461af2a26006224d273","contract":["procfs.DefaultMountPoint equals \"/proc\"","procfs.NewFS initializes an FS interface rooted at procfs.DefaultMountPoint","procfs.NewDefaultFS creates an FS instance using DefaultMountPoint","procfs.NewFS validates mount path and fails on non-existent directory or regular file"],"goal":"verify github.com/prometheus/procfs.DefaultMountPoint 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.DefaultMountPoint"]},"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@v0.6.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.6.0","symbols":["github.com/prometheus/procfs.DefaultMountPoint"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/prometheus/procfs v0.6.0

require golang.org/x/sys v0.47.0 // 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/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
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() {
	fmt.Printf("DefaultMountPoint: %s\n", procfs.DefaultMountPoint)

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

	self, err := fs.Self()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to get self process: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Current PID via DefaultMountPoint: %d\n", self.PID)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/procfs.DefaultMountPoint 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.DefaultMountPoint"
  ]
}

package main

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

	"github.com/prometheus/procfs"
)

func main() {
	// 1. procfs.DefaultMountPoint equals "/proc"
	if procfs.DefaultMountPoint != "/proc" {
		fmt.Fprintf(os.Stderr, "expected DefaultMountPoint to be '/proc', got %q\n", procfs.DefaultMountPoint)
		os.Exit(1)
	}

	// 2. procfs.NewFS initializes an FS interface rooted at procfs.DefaultMountPoint
	fs, err := procfs.NewFS(procfs.DefaultMountPoint)
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewFS(DefaultMountPoint) failed: %v\n", err)
		os.Exit(1)
	}

	self, err := fs.Self()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Self() failed: %v\n", err)
		os.Exit(1)
	}
	if self.PID <= 0 {
		fmt.Fprintf(os.Stderr, "expected positive PID from Self(), got %d\n", self.PID)
		os.Exit(1)
	}

	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 non-zero BootTime from fs.Stat()\n")
		os.Exit(1)
	}

	// 3. procfs.NewDefaultFS creates an FS instance using DefaultMountPoint
	defaultFS, err := procfs.NewDefaultFS()
	if err != nil {
		fmt.Fprintf(os.Stderr, "procfs.NewDefaultFS() failed: %v\n", err)
		os.Exit(1)
	}
	defaultSelf, err := defaultFS.Self()
	if err != nil {
		fmt.Fprintf(os.Stderr, "defaultFS.Self() failed: %v\n", err)
		os.Exit(1)
	}
	if defaultSelf.PID != self.PID {
		fmt.Fprintf(os.Stderr, "PID mismatch: defaultFS=%d, explicitFS=%d\n", defaultSelf.PID, self.PID)
		os.Exit(1)
	}

	// 4. procfs.NewFS validates mount path and fails on non-existent directory or regular file
	nonexistent := filepath.Join(os.TempDir(), "nonexistent-procfs-dir-99999")
	if _, err := procfs.NewFS(nonexistent); err == nil {
		fmt.Fprintf(os.Stderr, "expected NewFS to fail on nonexistent directory, but got nil error\n")
		os.Exit(1)
	}

	tmpFile := filepath.Join(os.TempDir(), "temp-procfs-regular-file")
	if err := os.WriteFile(tmpFile, []byte("regular file"), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(tmpFile)

	if _, err := procfs.NewFS(tmpFile); err == nil {
		fmt.Fprintf(os.Stderr, "expected NewFS to fail on regular file, but got nil error\n")
		os.Exit(1)
	}

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