golang.org/x/sys v0.31.0: unix.Write

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.Write in pkg:golang/golang.org/x/sys@v0.31.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.31.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Write
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:b69f1125f96d49cc47311d3851024d694b1b7801fb01fcacdf0be85d7e742016","contract":["unix.Write writes the entire byte buffer to a valid pipe file descriptor","unix.Write returns n=0 and nil error when writing an empty slice","unix.Write returns EBADF when writing to an invalid file descriptor","unix.Write returns EBADF when writing to a closed file descriptor","unix.Write preserves byte sequence and contents across sequential writes","unix.Write writes successfully to a regular file descriptor opened with O_WRONLY"],"goal":"verify golang.org/x/sys/unix.Write in pkg:golang/golang.org/x/sys@v0.31.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.31.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Write"]},"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@v0.31.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.31.0","symbols":["golang.org/x/sys/unix.Write"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require golang.org/x/sys v0.31.0 // indirect

golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=

package main

import (
	"fmt"
	"os"

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

func main() {
	var fds [2]int
	if err := unix.Pipe(fds[:]); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create pipe: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(fds[0])
	defer unix.Close(fds[1])

	message := []byte("Hello, unix.Write!")

	n, err := unix.Write(fds[1], message)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Write failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("Wrote %d bytes via unix.Write\n", n)

	buf := make([]byte, len(message))
	nRead, err := unix.Read(fds[0], buf)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Read failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("Read %d bytes: %s\n", nRead, string(buf[:nRead]))
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Write in pkg:golang/golang.org/x/sys@v0.31.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.31.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Write"
  ]
}

package main

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

	"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 tests passed successfully.")
}

func runTests() error {
	// 1. unix.Write writes the entire byte buffer to a valid pipe file descriptor
	var p1 [2]int
	if err := unix.Pipe(p1[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p1[0])
	defer unix.Close(p1[1])

	data := []byte("hello-unix-write")
	n, err := unix.Write(p1[1], data)
	if err != nil {
		return fmt.Errorf("unix.Write failed: %w", err)
	}
	if n != len(data) {
		return fmt.Errorf("expected %d bytes written, got %d", len(data), n)
	}
	readBuf := make([]byte, len(data))
	nr, err := unix.Read(p1[0], readBuf)
	if err != nil {
		return fmt.Errorf("unix.Read failed: %w", err)
	}
	if nr != len(data) || !bytes.Equal(readBuf[:nr], data) {
		return fmt.Errorf("read mismatch: expected %q, got %q", string(data), string(readBuf[:nr]))
	}

	// 2. unix.Write returns n=0 and nil error when writing an empty slice
	var p2 [2]int
	if err := unix.Pipe(p2[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p2[0])
	defer unix.Close(p2[1])

	nEmpty, err := unix.Write(p2[1], []byte{})
	if err != nil {
		return fmt.Errorf("unix.Write with empty slice returned error: %w", err)
	}
	if nEmpty != 0 {
		return fmt.Errorf("expected 0 bytes written for empty slice, got %d", nEmpty)
	}

	// 3. unix.Write returns EBADF when writing to an invalid file descriptor
	_, err = unix.Write(-1, []byte("data"))
	if err == nil {
		return fmt.Errorf("expected error writing to invalid fd -1, got nil")
	}
	if !errors.Is(err, unix.EBADF) {
		return fmt.Errorf("expected EBADF for fd -1, got: %v", err)
	}

	// 4. unix.Write returns EBADF when writing to a closed file descriptor
	var p4 [2]int
	if err := unix.Pipe(p4[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	unix.Close(p4[0])
	unix.Close(p4[1])

	_, err = unix.Write(p4[1], []byte("closed fd write"))
	if err == nil {
		return fmt.Errorf("expected error writing to closed fd, got nil")
	}
	if !errors.Is(err, unix.EBADF) {
		return fmt.Errorf("expected EBADF for closed fd, got: %v", err)
	}

	// 5. unix.Write preserves byte sequence and contents across sequential writes
	var p5 [2]int
	if err := unix.Pipe(p5[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p5[0])
	defer unix.Close(p5[1])

	chunk1 := []byte("first-chunk;")
	chunk2 := []byte("second-chunk;")
	chunk3 := []byte("third-chunk")
	for _, chunk := range [][]byte{chunk1, chunk2, chunk3} {
		nw, err := unix.Write(p5[1], chunk)
		if err != nil {
			return fmt.Errorf("sequential write failed: %w", err)
		}
		if nw != len(chunk) {
			return fmt.Errorf("expected %d bytes written, got %d", len(chunk), nw)
		}
	}

	expectedTotal := append(append(chunk1, chunk2...), chunk3...)
	buf5 := make([]byte, len(expectedTotal))
	nTotalRead := 0
	for nTotalRead < len(expectedTotal) {
		nr, err := unix.Read(p5[0], buf5[nTotalRead:])
		if err != nil {
			return fmt.Errorf("read failed during sequential check: %w", err)
		}
		nTotalRead += nr
	}
	if !bytes.Equal(buf5, expectedTotal) {
		return fmt.Errorf("sequential write content mismatch: expected %q, got %q", string(expectedTotal), string(buf5))
	}

	// 6. unix.Write writes successfully to a regular file descriptor opened with O_WRONLY
	tmpDir, err := os.MkdirTemp("", "csx-test-*")
	if err != nil {
		return fmt.Errorf("failed to create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	tmpFilePath := filepath.Join(tmpDir, "test.dat")
	fd, err := unix.Open(tmpFilePath, unix.O_CREAT|unix.O_WRONLY|unix.O_TRUNC, 0600)
	if err != nil {
		return fmt.Errorf("unix.Open failed: %w", err)
	}

	payload := []byte("file payload written with unix.Write")
	nWritten, err := unix.Write(fd, payload)
	unix.Close(fd)
	if err != nil {
		return fmt.Errorf("unix.Write to file failed: %w", err)
	}
	if nWritten != len(payload) {
		return fmt.Errorf("expected %d bytes written to file, got %d", len(payload), nWritten)
	}

	readFd, err := unix.Open(tmpFilePath, unix.O_RDONLY, 0)
	if err != nil {
		return fmt.Errorf("unix.Open for read failed: %w", err)
	}
	defer unix.Close(readFd)

	readFileBuf := make([]byte, len(payload)+10)
	nrFile, err := unix.Read(readFd, readFileBuf)
	if err != nil {
		return fmt.Errorf("unix.Read from file failed: %w", err)
	}
	if nrFile != len(payload) || !bytes.Equal(readFileBuf[:nrFile], payload) {
		return fmt.Errorf("file content mismatch: expected %q, got %q", string(payload), string(readFileBuf[:nrFile]))
	}

	return nil
}