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

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.O_WRONLY 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.O_WRONLY

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:sha256:2b6c9580fcd36845ff3f08dde65f5b38383d035c83b999f263af3713a8e8c1dc","contract":["unix.O_WRONLY flag equals 1 and satisfies (unix.O_WRONLY \u0026 unix.O_ACCMODE) == unix.O_WRONLY","unix.Open with unix.O_WRONLY opens a file for writing and rejects read operations with EBADF","unix.Open with unix.O_RDONLY opens a file for reading and rejects write operations with EBADF"],"goal":"verify golang.org/x/sys/unix.O_WRONLY 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.O_WRONLY"]},"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.O_WRONLY"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

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

	fd, err := unix.Open(tmpFile.Name(), unix.O_WRONLY|unix.O_TRUNC, 0600)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open failed: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(fd)

	msg := []byte("hello from unix.O_WRONLY")
	n, err := unix.Write(fd, msg)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Write failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Successfully wrote %d bytes using O_WRONLY (flag value: %d)\n", n, unix.O_WRONLY)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.O_WRONLY 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.O_WRONLY"
  ]
}

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 {
	// 1. unix.O_WRONLY flag equals 1 and satisfies (unix.O_WRONLY & unix.O_ACCMODE) == unix.O_WRONLY
	if unix.O_WRONLY != 1 {
		return fmt.Errorf("expected unix.O_WRONLY == 1, got %d", unix.O_WRONLY)
	}
	if (unix.O_WRONLY & unix.O_ACCMODE) != unix.O_WRONLY {
		return fmt.Errorf("expected unix.O_WRONLY & unix.O_ACCMODE == unix.O_WRONLY")
	}

	// 2. unix.Open with unix.O_WRONLY opens a file for writing and rejects read operations with EBADF
	tmpFile, err := os.CreateTemp("", "owronly_contract_*")
	if err != nil {
		return fmt.Errorf("failed to create temp file: %w", err)
	}
	tmpPath := tmpFile.Name()
	tmpFile.Close()
	defer os.Remove(tmpPath)

	wfd, err := unix.Open(tmpPath, unix.O_WRONLY|unix.O_TRUNC, 0600)
	if err != nil {
		return fmt.Errorf("unix.Open with O_WRONLY failed: %w", err)
	}
	defer unix.Close(wfd)

	payload := []byte("CodeSampleX contract verification payload")
	n, err := unix.Write(wfd, payload)
	if err != nil {
		return fmt.Errorf("unix.Write on O_WRONLY fd failed: %w", err)
	}
	if n != len(payload) {
		return fmt.Errorf("expected to write %d bytes, wrote %d", len(payload), n)
	}

	readBuf := make([]byte, 32)
	_, rerr := unix.Read(wfd, readBuf)
	if rerr == nil {
		return fmt.Errorf("expected unix.Read on O_WRONLY fd to fail, but succeeded")
	}
	if !errors.Is(rerr, unix.EBADF) {
		return fmt.Errorf("expected unix.Read to fail with EBADF, got: %v", rerr)
	}

	// 3. unix.Open with unix.O_RDONLY opens a file for reading and rejects write operations with EBADF
	rfd, err := unix.Open(tmpPath, unix.O_RDONLY, 0)
	if err != nil {
		return fmt.Errorf("unix.Open with O_RDONLY failed: %w", err)
	}
	defer unix.Close(rfd)

	rn, err := unix.Read(rfd, readBuf)
	if err != nil {
		return fmt.Errorf("unix.Read on O_RDONLY fd failed: %w", err)
	}
	if rn != len(readBuf) {
		return fmt.Errorf("expected to read %d bytes, got %d", len(readBuf), rn)
	}

	_, werr := unix.Write(rfd, []byte("should fail"))
	if werr == nil {
		return fmt.Errorf("expected unix.Write on O_RDONLY fd to fail, but succeeded")
	}
	if !errors.Is(werr, unix.EBADF) {
		return fmt.Errorf("expected unix.Write on O_RDONLY to fail with EBADF, got: %v", werr)
	}

	return nil
}