golang.org/x/sys v0.22.0: unix.Fstat

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.Fstat in pkg:golang/golang.org/x/sys@v0.22.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.22.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Fstat

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:f954669201f11d3cf1e5c6f9d3c014c28c1a73473145da35d82be247a9c719de","contract":["unix.Fstat populates a Stat_t struct with accurate size, mode, inode, and link count for an open file descriptor","unix.Fstat detects file type flags including regular file (S_IFREG) and pipe FIFO (S_IFIFO)","unix.Fstat returns EBADF error when invoked on an invalid or closed file descriptor"],"goal":"verify golang.org/x/sys/unix.Fstat in pkg:golang/golang.org/x/sys@v0.22.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.22.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Fstat"]},"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@v0.22.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.22.0","symbols":["golang.org/x/sys/unix.Fstat"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22.0

require golang.org/x/sys v0.22.0

golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

package main

import (
	"fmt"
	"os"

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

func main() {
	tmpFile, err := os.CreateTemp("", "fstat-demo-*")
	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()

	content := []byte("Hello, CodeSampleX unix.Fstat verification!")
	if _, err := tmpFile.Write(content); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write to file: %v\n", err)
		os.Exit(1)
	}

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

	fmt.Printf("File size: %d bytes\n", stat.Size)
	fmt.Printf("File mode: 0%o\n", stat.Mode)
	fmt.Printf("Inode: %d\n", stat.Ino)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Fstat in pkg:golang/golang.org/x/sys@v0.22.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.22.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Fstat"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

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

func main() {
	// Assertion 1: unix.Fstat populates a Stat_t struct with accurate size, mode, inode, and link count for an open file descriptor
	tmpFile, err := os.CreateTemp("", "fstat-contract-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: failed to create temporary file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(tmpFile.Name())
	defer tmpFile.Close()

	payload := []byte("CodeSampleX contract test payload for Fstat")
	if _, err := tmpFile.Write(payload); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: failed to write test payload: %v\n", err)
		os.Exit(1)
	}

	var stat unix.Stat_t
	fd := int(tmpFile.Fd())
	if err := unix.Fstat(fd, &stat); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Fstat on open file descriptor returned error: %v\n", err)
		os.Exit(1)
	}

	if stat.Size != int64(len(payload)) {
		fmt.Fprintf(os.Stderr, "FAIL: expected size %d, got %d\n", len(payload), stat.Size)
		os.Exit(1)
	}

	if stat.Mode&unix.S_IFREG == 0 {
		fmt.Fprintf(os.Stderr, "FAIL: expected regular file mode (S_IFREG), got mode 0%o\n", stat.Mode)
		os.Exit(1)
	}

	if stat.Ino == 0 {
		fmt.Fprintf(os.Stderr, "FAIL: expected non-zero inode number\n")
		os.Exit(1)
	}

	if stat.Nlink == 0 {
		fmt.Fprintf(os.Stderr, "FAIL: expected positive link count\n")
		os.Exit(1)
	}

	// Assertion 2: unix.Fstat detects file type flags including regular file (S_IFREG) and pipe FIFO (S_IFIFO)
	pipeFds := make([]int, 2)
	if err := unix.Pipe(pipeFds); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe failed: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(pipeFds[0])
	defer unix.Close(pipeFds[1])

	var pipeStat unix.Stat_t
	if err := unix.Fstat(pipeFds[0], &pipeStat); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Fstat on pipe read end failed: %v\n", err)
		os.Exit(1)
	}

	if pipeStat.Mode&unix.S_IFIFO == 0 {
		fmt.Fprintf(os.Stderr, "FAIL: expected FIFO mode (S_IFIFO) for pipe, got mode 0%o\n", pipeStat.Mode)
		os.Exit(1)
	}

	// Assertion 3: unix.Fstat returns EBADF error when invoked on an invalid or closed file descriptor
	var badStat unix.Stat_t
	err = unix.Fstat(-1, &badStat)
	if err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected error on fd -1, got nil\n")
		os.Exit(1)
	}
	if !errors.Is(err, unix.EBADF) {
		fmt.Fprintf(os.Stderr, "FAIL: expected EBADF on fd -1, got %v\n", err)
		os.Exit(1)
	}

	// Test closed file descriptor
	closedFile, err := os.CreateTemp("", "fstat-closed-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: failed to create temporary file for closed test: %v\n", err)
		os.Exit(1)
	}
	closedFd := int(closedFile.Fd())
	os.Remove(closedFile.Name())
	closedFile.Close()

	err = unix.Fstat(closedFd, &badStat)
	if err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected error on closed fd %d, got nil\n", closedFd)
		os.Exit(1)
	}
	if !errors.Is(err, unix.EBADF) {
		fmt.Fprintf(os.Stderr, "FAIL: expected EBADF on closed fd %d, got %v\n", closedFd, err)
		os.Exit(1)
	}

	fmt.Println("PASS: golang.org/x/sys/unix.Fstat contract passed")
}