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

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@v0.6.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/procfs@v0.6.0

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:e5154c84c36686f48cdb75af1bd4da96a11d4a68945bdf0d6329d991766d0739","contract":["procfs.DefaultMountPoint equals \"/proc\"","procfs.NewFS fails on nonexistent directory path","procfs.NewFS initializes an FS instance for a valid directory","FS.Proc returns a Proc instance for a valid PID directory","Proc.Stat reads process stat information (comm, state, ppid)","Proc.Comm reads process command name","Proc.CmdLine reads process command line arguments","FS.AllProcs enumerates all processes in the filesystem"],"goal":"verify 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.NewFS"]},"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.NewFS"],"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/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.NewFS(procfs.DefaultMountPoint)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to initialize procfs: %v\n", err)
		os.Exit(1)
	}

	procs, err := fs.AllProcs()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to list processes: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Initialized procfs at %s, found %d processes\n", procfs.DefaultMountPoint, len(procs))
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/prometheus/procfs@v0.6.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/procfs@v0.6.0"
  ]
}

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 fails on nonexistent directory path
	nonexistent := filepath.Join(os.TempDir(), "nonexistent-procfs-dir-99999")
	_, err := procfs.NewFS(nonexistent)
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected NewFS to fail on nonexistent directory, but got nil error\n")
		os.Exit(1)
	}

	// 3. procfs.NewFS initializes an FS instance for a valid 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)

	pidDir := filepath.Join(mockDir, "123")
	if err := os.MkdirAll(pidDir, 0755); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create mock pid directory: %v\n", err)
		os.Exit(1)
	}

	statContent := "123 (testproc) S 1 123 123 0 -1 4194304 100 0 0 0 10 20 0 0 20 0 1 0 123456 1000000 500 18446744073709551615 0 0 0 0 0 0 0 0 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0\n"
	if err := os.WriteFile(filepath.Join(pidDir, "stat"), []byte(statContent), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write mock stat: %v\n", err)
		os.Exit(1)
	}
	if err := os.WriteFile(filepath.Join(pidDir, "comm"), []byte("testproc\n"), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write mock comm: %v\n", err)
		os.Exit(1)
	}
	if err := os.WriteFile(filepath.Join(pidDir, "cmdline"), []byte("testproc\x00--arg1\x00val1\x00"), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write mock cmdline: %v\n", err)
		os.Exit(1)
	}

	fs, err := procfs.NewFS(mockDir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "expected NewFS to succeed for valid directory: %v\n", err)
		os.Exit(1)
	}

	// 4. FS.Proc returns a Proc instance for a valid PID directory
	proc, err := fs.Proc(123)
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.Proc(123) failed: %v\n", err)
		os.Exit(1)
	}
	if proc.PID != 123 {
		fmt.Fprintf(os.Stderr, "expected proc.PID 123, got %d\n", proc.PID)
		os.Exit(1)
	}

	// 5. Proc.Stat reads process stat information (comm, state, ppid)
	stat, err := proc.Stat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "proc.Stat() failed: %v\n", err)
		os.Exit(1)
	}
	if stat.Comm != "testproc" {
		fmt.Fprintf(os.Stderr, "expected stat.Comm 'testproc', got %q\n", stat.Comm)
		os.Exit(1)
	}
	if stat.State != "S" {
		fmt.Fprintf(os.Stderr, "expected stat.State 'S', got %q\n", stat.State)
		os.Exit(1)
	}
	if stat.PPID != 1 {
		fmt.Fprintf(os.Stderr, "expected stat.PPID 1, got %d\n", stat.PPID)
		os.Exit(1)
	}

	// 6. Proc.Comm reads process command name
	comm, err := proc.Comm()
	if err != nil {
		fmt.Fprintf(os.Stderr, "proc.Comm() failed: %v\n", err)
		os.Exit(1)
	}
	if comm != "testproc" {
		fmt.Fprintf(os.Stderr, "expected comm 'testproc', got %q\n", comm)
		os.Exit(1)
	}

	// 7. Proc.CmdLine reads process command line arguments
	cmdline, err := proc.CmdLine()
	if err != nil {
		fmt.Fprintf(os.Stderr, "proc.CmdLine() failed: %v\n", err)
		os.Exit(1)
	}
	if len(cmdline) != 3 || cmdline[0] != "testproc" || cmdline[1] != "--arg1" || cmdline[2] != "val1" {
		fmt.Fprintf(os.Stderr, "unexpected cmdline slice: %#v\n", cmdline)
		os.Exit(1)
	}

	// 8. FS.AllProcs enumerates all processes in the filesystem
	allProcs, err := fs.AllProcs()
	if err != nil {
		fmt.Fprintf(os.Stderr, "fs.AllProcs() failed: %v\n", err)
		os.Exit(1)
	}
	if len(allProcs) != 1 || allProcs[0].PID != 123 {
		fmt.Fprintf(os.Stderr, "expected exactly 1 proc with PID 123, got: %#v\n", allProcs)
		os.Exit(1)
	}

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