golang.org/x/sys v0.41.0: unix.Fstatfs

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 golang.org/x/sys/unix.Fstatfs in pkg:golang/golang.org/x/sys@v0.41.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.41.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Fstatfs

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:sha256:41b4ca781e13588acd561c0a449b98cdd80e4db672cd10f8e2836b76d05f198d","contract":["unix.Fstatfs retrieves filesystem statistics for a valid open file descriptor","unix.Fstatfs populates positive Bsize and Blocks in Statfs_t","unix.Fstatfs returns unix.EBADF for an invalid file descriptor","unix.Fstatfs returns unix.EBADF after a file descriptor is closed"],"goal":"verify golang.org/x/sys/unix.Fstatfs in pkg:golang/golang.org/x/sys@v0.41.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.41.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Fstatfs"]},"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/golang.org/x/sys@v0.41.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.41.0","symbols":["golang.org/x/sys/unix.Fstatfs"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/sys v0.41.0

golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=

package main

import (
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	tmpFile, err := os.CreateTemp("", "fstatfs_sample_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(tmpFile.Name())
	defer tmpFile.Close()

	var buf unix.Statfs_t
	if err := unix.Fstatfs(int(tmpFile.Fd()), &buf); err != nil {
		fmt.Fprintf(os.Stderr, "unix.Fstatfs failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Fstatfs succeeded: Type=0x%x, Bsize=%d, Blocks=%d, Bavail=%d\n",
		buf.Type, buf.Bsize, buf.Blocks, buf.Bavail)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Fstatfs in pkg:golang/golang.org/x/sys@v0.41.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.41.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Fstatfs"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	if err := runTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract assertions passed.")
}

func runTests() error {
	tmpFile, err := os.CreateTemp("", "contract_fstatfs_*")
	if err != nil {
		return fmt.Errorf("failed to create temp file: %w", err)
	}
	defer os.Remove(tmpFile.Name())

	fd := int(tmpFile.Fd())

	// 1. unix.Fstatfs retrieves filesystem statistics for a valid open file descriptor
	var buf unix.Statfs_t
	if err := unix.Fstatfs(fd, &buf); err != nil {
		tmpFile.Close()
		return fmt.Errorf("unix.Fstatfs failed on valid fd: %w", err)
	}

	// 2. unix.Fstatfs populates positive Bsize and Blocks in Statfs_t
	if buf.Bsize <= 0 {
		tmpFile.Close()
		return fmt.Errorf("expected positive Bsize, got %d", buf.Bsize)
	}
	if buf.Blocks == 0 {
		tmpFile.Close()
		return fmt.Errorf("expected non-zero Blocks, got %d", buf.Blocks)
	}

	// 3. unix.Fstatfs returns unix.EBADF for an invalid file descriptor
	var invalidBuf unix.Statfs_t
	err = unix.Fstatfs(-1, &invalidBuf)
	if err == nil {
		tmpFile.Close()
		return fmt.Errorf("expected unix.Fstatfs(-1) to fail, but succeeded")
	}
	if !errors.Is(err, unix.EBADF) {
		tmpFile.Close()
		return fmt.Errorf("expected unix.EBADF for fd=-1, got: %w", err)
	}

	// 4. unix.Fstatfs returns unix.EBADF after a file descriptor is closed
	if err := tmpFile.Close(); err != nil {
		return fmt.Errorf("failed to close temp file: %w", err)
	}
	var closedBuf unix.Statfs_t
	err = unix.Fstatfs(fd, &closedBuf)
	if err == nil {
		return fmt.Errorf("expected unix.Fstatfs on closed fd to fail, but succeeded")
	}
	if !errors.Is(err, unix.EBADF) {
		return fmt.Errorf("expected unix.EBADF for closed fd, got: %w", err)
	}

	return nil
}