golang.org/x/sys v0.31.0: unix.Pipe2

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.Pipe2 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.Pipe2

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:sha256:3135de5d2d5e829ba466ddec64658d6c29d5722a3b3d25c4e44164a42a9fb10f","contract":["unix.Pipe2 creates connected read and write file descriptors with default flags (0)","unix.Pipe2 with unix.O_CLOEXEC sets the FD_CLOEXEC flag on both descriptors","unix.Pipe2 with unix.O_NONBLOCK creates descriptors returning EAGAIN or EWOULDBLOCK on empty read","unix.Pipe2 transfers data from write descriptor to read descriptor preserving byte integrity","unix.Pipe2 returns EINVAL when provided a descriptor slice with length less than 2"],"goal":"verify golang.org/x/sys/unix.Pipe2 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.Pipe2"]},"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.Pipe2"],"verifierAdapter":"golang@1"}

module sample

go 1.25.0

require golang.org/x/sys v0.31.0

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

package main

import (
	"errors"
	"fmt"
	"os"

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

// OpenPipe creates a pipe with the given flags using unix.Pipe2.
func OpenPipe(flags int) ([2]int, error) {
	var fds [2]int
	if err := unix.Pipe2(fds[:], flags); err != nil {
		return fds, fmt.Errorf("pipe2 failed: %w", err)
	}
	return fds, nil
}

func main() {
	// Create a non-blocking, close-on-exec pipe using unix.Pipe2
	fds, err := OpenPipe(unix.O_CLOEXEC | unix.O_NONBLOCK)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error creating pipe: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(fds[0])
	defer unix.Close(fds[1])

	// Attempt reading from empty non-blocking pipe
	buf := make([]byte, 128)
	n, err := unix.Read(fds[0], buf)
	if err != nil && (errors.Is(err, unix.EAGAIN) || errors.Is(err, unix.EWOULDBLOCK)) {
		fmt.Println("Confirmed non-blocking behavior: read returned EAGAIN/EWOULDBLOCK on empty pipe")
	} else if err != nil {
		fmt.Fprintf(os.Stderr, "Unexpected read error: %v\n", err)
		os.Exit(1)
	} else {
		fmt.Fprintf(os.Stderr, "Unexpected read result: %d bytes\n", n)
		os.Exit(1)
	}

	// Write data through the write end
	message := []byte("hello from unix.Pipe2")
	wn, err := unix.Write(fds[1], message)
	if err != nil || wn != len(message) {
		fmt.Fprintf(os.Stderr, "Write failed: %v\n", err)
		os.Exit(1)
	}

	// Read data from the read end
	rn, err := unix.Read(fds[0], buf)
	if err != nil || rn != len(message) {
		fmt.Fprintf(os.Stderr, "Read failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Successfully transferred %d bytes: %s\n", rn, string(buf[:rn]))
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Pipe2 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.Pipe2"
  ]
}

package main

import (
	"bytes"
	"errors"
	"fmt"
	"os"

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

func main() {
	// Assertion 1: unix.Pipe2 creates connected read and write file descriptors with default flags (0)
	var defaultFds [2]int
	if err := unix.Pipe2(defaultFds[:], 0); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe2 with flag 0 failed: %v\n", err)
		os.Exit(1)
	}
	if defaultFds[0] < 0 || defaultFds[1] < 0 {
		fmt.Fprintf(os.Stderr, "FAIL: invalid descriptors returned: %v\n", defaultFds)
		os.Exit(1)
	}
	_ = unix.Close(defaultFds[0])
	_ = unix.Close(defaultFds[1])

	// Assertion 2: unix.Pipe2 with unix.O_CLOEXEC sets the FD_CLOEXEC flag on both descriptors
	var cloexecFds [2]int
	if err := unix.Pipe2(cloexecFds[:], unix.O_CLOEXEC); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe2 with O_CLOEXEC failed: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(cloexecFds[0])
	defer unix.Close(cloexecFds[1])

	for i, fd := range cloexecFds {
		flags, err := unix.FcntlInt(uintptr(fd), unix.F_GETFD, 0)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: fcntl F_GETFD on fd %d failed: %v\n", fd, err)
			os.Exit(1)
		}
		if (flags & unix.FD_CLOEXEC) == 0 {
			fmt.Fprintf(os.Stderr, "FAIL: FD_CLOEXEC not set on fd index %d (%d)\n", i, fd)
			os.Exit(1)
		}
	}

	// Assertion 3: unix.Pipe2 with unix.O_NONBLOCK creates descriptors returning EAGAIN or EWOULDBLOCK on empty read
	var nbFds [2]int
	if err := unix.Pipe2(nbFds[:], unix.O_NONBLOCK); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe2 with O_NONBLOCK failed: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(nbFds[0])
	defer unix.Close(nbFds[1])

	fl, err := unix.FcntlInt(uintptr(nbFds[0]), unix.F_GETFL, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: fcntl F_GETFL failed: %v\n", err)
		os.Exit(1)
	}
	if (fl & unix.O_NONBLOCK) == 0 {
		fmt.Fprintf(os.Stderr, "FAIL: O_NONBLOCK flag not set on read fd\n")
		os.Exit(1)
	}

	buf := make([]byte, 64)
	n, err := unix.Read(nbFds[0], buf)
	if err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected EAGAIN/EWOULDBLOCK on empty read, got %d bytes\n", n)
		os.Exit(1)
	}
	if !errors.Is(err, unix.EAGAIN) && !errors.Is(err, unix.EWOULDBLOCK) {
		fmt.Fprintf(os.Stderr, "FAIL: expected EAGAIN or EWOULDBLOCK, got %v\n", err)
		os.Exit(1)
	}

	// Assertion 4: unix.Pipe2 transfers data from write descriptor to read descriptor preserving byte integrity
	payload := []byte("pipe2-contract-test-data-12345")
	wn, err := unix.Write(nbFds[1], payload)
	if err != nil || wn != len(payload) {
		fmt.Fprintf(os.Stderr, "FAIL: write to pipe failed: wn=%d, err=%v\n", wn, err)
		os.Exit(1)
	}

	readBuf := make([]byte, 64)
	rn, err := unix.Read(nbFds[0], readBuf)
	if err != nil || rn != len(payload) || !bytes.Equal(readBuf[:rn], payload) {
		fmt.Fprintf(os.Stderr, "FAIL: read verification failed: rn=%d, err=%v, data=%q\n", rn, err, string(readBuf[:rn]))
		os.Exit(1)
	}

	// Assertion 5: unix.Pipe2 returns EINVAL when provided a descriptor slice with length less than 2
	shortSlice := make([]int, 1)
	if err := unix.Pipe2(shortSlice, 0); !errors.Is(err, unix.EINVAL) {
		fmt.Fprintf(os.Stderr, "FAIL: expected EINVAL for slice length < 2, got: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("PASS: all contract assertions passed")
}