github.com/prometheus/procfs v0.6.0: 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 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.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:ae9b348609202765c2451984b12b43f1cacf7003a366c8e88c6fb540e8d1d3d4","contract":["procfs.NewFS initializes an FS instance for a valid directory","FS.NetDev returns error when net/dev does not exist","FS.NetDev returns error on malformed net/dev content","FS.NetDev parses interface statistics from net/dev (RxBytes, RxPackets, TxBytes, TxPackets)","NetDev.Total aggregates metrics across all network interfaces"],"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.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@v0.6.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/procfs@v0.6.0","symbols":["github.com/prometheus/procfs.FS.NetDev"],"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 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 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 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)
	}

	total := netDev.Total()
	fmt.Printf("Parsed %d network interfaces, total RxBytes: %d, total TxBytes: %d\n",
		len(netDev), total.RxBytes, total.TxBytes)
}

{
  "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"
  ],
  "symbols": [
    "github.com/prometheus/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, "expected NewFS to succeed for valid directory: %v\n", err)
		os.Exit(1)
	}

	// 2. FS.NetDev returns error when net/dev does not exist
	_, err = fs.NetDev()
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected NetDev to fail when net/dev does not exist\n")
		os.Exit(1)
	}

	// 3. FS.NetDev returns error on malformed net/dev content
	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)
	}

	malformedContent := "header line 1\nheader line 2\nmalformed line without colon\n"
	if err := os.WriteFile(filepath.Join(netDir, "dev"), []byte(malformedContent), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write malformed dev file: %v\n", err)
		os.Exit(1)
	}

	_, err = fs.NetDev()
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected NetDev to fail on malformed content\n")
		os.Exit(1)
	}

	// 4. FS.NetDev parses interface statistics from net/dev (RxBytes, RxPackets, TxBytes, TxPackets)
	validDevContent := `Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
    lo: 1000       10    1    0    0     0          0         0     2000       20    2    0    0     0       0          0
  eth0: 5000       50    0    0    0     0          0         0     6000       60    0    0    0     0       0          0
`
	if err := os.WriteFile(filepath.Join(netDir, "dev"), []byte(validDevContent), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write valid dev file: %v\n", err)
		os.Exit(1)
	}

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

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

	lo, ok := netDev["lo"]
	if !ok {
		fmt.Fprintf(os.Stderr, "expected interface 'lo' to be present\n")
		os.Exit(1)
	}
	if lo.Name != "lo" || lo.RxBytes != 1000 || lo.RxPackets != 10 || lo.RxErrors != 1 ||
		lo.TxBytes != 2000 || lo.TxPackets != 20 || lo.TxErrors != 2 {
		fmt.Fprintf(os.Stderr, "unexpected metrics for 'lo': %+v\n", lo)
		os.Exit(1)
	}

	eth0, ok := netDev["eth0"]
	if !ok {
		fmt.Fprintf(os.Stderr, "expected interface 'eth0' to be present\n")
		os.Exit(1)
	}
	if eth0.Name != "eth0" || eth0.RxBytes != 5000 || eth0.RxPackets != 50 ||
		eth0.TxBytes != 6000 || eth0.TxPackets != 60 {
		fmt.Fprintf(os.Stderr, "unexpected metrics for 'eth0': %+v\n", eth0)
		os.Exit(1)
	}

	// 5. NetDev.Total aggregates metrics across all network interfaces
	total := netDev.Total()
	if total.RxBytes != 6000 {
		fmt.Fprintf(os.Stderr, "expected total RxBytes 6000, got %d\n", total.RxBytes)
		os.Exit(1)
	}
	if total.RxPackets != 60 {
		fmt.Fprintf(os.Stderr, "expected total RxPackets 60, got %d\n", total.RxPackets)
		os.Exit(1)
	}
	if total.TxBytes != 8000 {
		fmt.Fprintf(os.Stderr, "expected total TxBytes 8000, got %d\n", total.TxBytes)
		os.Exit(1)
	}
	if total.TxPackets != 80 {
		fmt.Fprintf(os.Stderr, "expected total TxPackets 80, got %d\n", total.TxPackets)
		os.Exit(1)
	}
	if total.Name != "eth0, lo" {
		fmt.Fprintf(os.Stderr, "expected total Name 'eth0, lo', got %q\n", total.Name)
		os.Exit(1)
	}

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