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

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 procfs.FS.NetDev in 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.NetDev

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:sha256:1c5583f7b90088eaa538b3f056cc3b32c76d9157091c5019fa030854aed6df21","contract":["procfs.NewFS initializes an FS instance for a valid directory","procfs.FS.NetDev returns an error when net/dev does not exist","procfs.FS.NetDev parses /proc/net/dev and returns device statistics by interface name","procfs.NetDev.Total calculates cumulative network statistics across all interfaces"],"goal":"verify procfs.FS.NetDev in 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.NetDev"]},"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.NetDev"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.25.0

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"
)

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

	netDev, err := fs.NetDev()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read net/dev: %v\n", err)
		os.Exit(1)
	}

	for iface, stats := range netDev {
		fmt.Printf("%s: rx_bytes=%d, tx_bytes=%d\n", iface, stats.RxBytes, stats.TxBytes)
	}

	total := netDev.Total()
	fmt.Printf("Total: rx_bytes=%d, tx_bytes=%d\n", total.RxBytes, total.TxBytes)
}

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

package main

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

	"github.com/prometheus/procfs"
)

func main() {
	// 1. 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)

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

	// 2. procfs.FS.NetDev returns an error when net/dev does not exist
	if _, err := fs.NetDev(); err == nil {
		fmt.Fprintf(os.Stderr, "contract failed: expected error when net/dev does not exist, got nil\n")
		os.Exit(1)
	}

	// 3. procfs.FS.NetDev parses /proc/net/dev and returns device statistics by interface name
	netDir := filepath.Join(mockDir, "net")
	if err := os.MkdirAll(netDir, 0755); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create mock net directory: %v\n", err)
		os.Exit(1)
	}

	mockDevData := "Inter-|   Receive                                                |  Transmit\n" +
		" face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed\n" +
		"    lo:    1024       16    0    0    0     0          0         0     1024       16    0    0    0     0       0          0\n" +
		"  eth0: 2097152    16384    1    2    3     4          0         5  1048576     8192    6    7    8     9      10          0\n"

	if err := os.WriteFile(filepath.Join(netDir, "dev"), []byte(mockDevData), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write mock net/dev: %v\n", err)
		os.Exit(1)
	}

	netDev, err := fs.NetDev()
	if err != nil {
		fmt.Fprintf(os.Stderr, "contract failed: fs.NetDev() returned error: %v\n", err)
		os.Exit(1)
	}

	if len(netDev) != 2 {
		fmt.Fprintf(os.Stderr, "contract failed: expected 2 interfaces, got %d\n", len(netDev))
		os.Exit(1)
	}

	lo, ok := netDev["lo"]
	if !ok {
		fmt.Fprintf(os.Stderr, "contract failed: 'lo' interface missing in netDev map\n")
		os.Exit(1)
	}
	if lo.Name != "lo" || lo.RxBytes != 1024 || lo.TxBytes != 1024 || lo.RxPackets != 16 || lo.TxPackets != 16 {
		fmt.Fprintf(os.Stderr, "contract failed: unexpected stats for 'lo': %+v\n", lo)
		os.Exit(1)
	}

	eth0, ok := netDev["eth0"]
	if !ok {
		fmt.Fprintf(os.Stderr, "contract failed: 'eth0' interface missing in netDev map\n")
		os.Exit(1)
	}
	if eth0.Name != "eth0" || eth0.RxBytes != 2097152 || eth0.TxBytes != 1048576 || eth0.RxPackets != 16384 || eth0.TxPackets != 8192 {
		fmt.Fprintf(os.Stderr, "contract failed: unexpected byte/packet counts for 'eth0': %+v\n", eth0)
		os.Exit(1)
	}
	if eth0.RxErrors != 1 || eth0.RxDropped != 2 || eth0.RxFIFO != 3 || eth0.RxFrame != 4 || eth0.RxMulticast != 5 {
		fmt.Fprintf(os.Stderr, "contract failed: unexpected rx detail for 'eth0': %+v\n", eth0)
		os.Exit(1)
	}
	if eth0.TxErrors != 6 || eth0.TxDropped != 7 || eth0.TxFIFO != 8 || eth0.TxCollisions != 9 || eth0.TxCarrier != 10 {
		fmt.Fprintf(os.Stderr, "contract failed: unexpected tx detail for 'eth0': %+v\n", eth0)
		os.Exit(1)
	}

	// 4. procfs.NetDev.Total calculates cumulative network statistics across all interfaces
	total := netDev.Total()
	expectedRxBytes := uint64(1024 + 2097152)
	expectedTxBytes := uint64(1024 + 1048576)
	expectedRxPackets := uint64(16 + 16384)
	expectedTxPackets := uint64(16 + 8192)

	if total.RxBytes != expectedRxBytes {
		fmt.Fprintf(os.Stderr, "contract failed: expected total RxBytes %d, got %d\n", expectedRxBytes, total.RxBytes)
		os.Exit(1)
	}
	if total.TxBytes != expectedTxBytes {
		fmt.Fprintf(os.Stderr, "contract failed: expected total TxBytes %d, got %d\n", expectedTxBytes, total.TxBytes)
		os.Exit(1)
	}
	if total.RxPackets != expectedRxPackets {
		fmt.Fprintf(os.Stderr, "contract failed: expected total RxPackets %d, got %d\n", expectedRxPackets, total.RxPackets)
		os.Exit(1)
	}
	if total.TxPackets != expectedTxPackets {
		fmt.Fprintf(os.Stderr, "contract failed: expected total TxPackets %d, got %d\n", expectedTxPackets, total.TxPackets)
		os.Exit(1)
	}

	fmt.Println("PASS")
}