golang.org/x/sys v0.0.0-20220406155245-289d7a0edf71: unix.Open

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.Open in pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Open

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:sha256:2f7efe9d2cc7a18b487048ddff41fc5e5d3c37776e9387cec0f0325b5d0ff8f7","contract":["unix.Open opens an existing file with O_RDONLY and returns a non-negative file descriptor","unix.Open with O_RDWR | O_CREAT creates a new file with specified permission bits and returns a valid file descriptor","unix.Open with O_CREAT | O_EXCL on an existing file fails with unix.EEXIST error","unix.Open on a non-existent path without O_CREAT fails with unix.ENOENT error","unix.Open with O_WRONLY | O_APPEND writes data at the end of an existing file preserving prior contents","unix.Open with O_WRONLY | O_TRUNC truncates an existing file to zero length on open","unix.Open with O_CLOEXEC sets the close-on-exec flag on the opened file descriptor"],"goal":"verify golang.org/x/sys/unix.Open in pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Open"]},"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@v0.0.0-20220406155245-289d7a0edf71"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71","symbols":["golang.org/x/sys/unix.Open"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.25.0

require golang.org/x/sys v0.0.0-20220406155245-289d7a0edf71

golang.org/x/sys v0.0.0-20220406155245-289d7a0edf71 h1:PRD0hj6tTuUnCFD08vkvjkYFbQg/9lV8KIxe1y4/cvU=
golang.org/x/sys v0.0.0-20220406155245-289d7a0edf71/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

package main

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

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

func main() {
	tmpDir, err := os.MkdirTemp("", "unix-open-demo-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	filePath := filepath.Join(tmpDir, "example.txt")

	// 1. Create and write to file using unix.Open with O_CREAT | O_RDWR
	fd, err := unix.Open(filePath, unix.O_CREAT|unix.O_RDWR|unix.O_CLOEXEC, 0644)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to open file for writing: %v\n", err)
		os.Exit(1)
	}

	msg := []byte("Hello from golang.org/x/sys/unix.Open!\n")
	n, err := unix.Write(fd, msg)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to write: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	fmt.Printf("Wrote %d bytes via fd %d\n", n, fd)
	unix.Close(fd)

	// 2. Read back using unix.Open with O_RDONLY
	readFd, err := unix.Open(filePath, unix.O_RDONLY|unix.O_CLOEXEC, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to open file for reading: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(readFd)

	buf := make([]byte, 128)
	readBytes, err := unix.Read(readFd, buf)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("Read %d bytes: %s", readBytes, string(buf[:readBytes]))
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Open in pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.0.0-20220406155245-289d7a0edf71"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Open"
  ]
}

package main

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

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

func main() {
	tmpDir, err := os.MkdirTemp("", "unix-open-contract-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	// 1. unix.Open opens an existing file with O_RDONLY and returns a non-negative file descriptor
	existingFile := filepath.Join(tmpDir, "existing.txt")
	testData := []byte("hello unix open\n")
	if err := os.WriteFile(existingFile, testData, 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create test file: %v\n", err)
		os.Exit(1)
	}

	fd, err := unix.Open(existingFile, unix.O_RDONLY, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open O_RDONLY failed: %v\n", err)
		os.Exit(1)
	}
	if fd < 0 {
		fmt.Fprintf(os.Stderr, "unix.Open returned negative fd: %d\n", fd)
		os.Exit(1)
	}

	buf := make([]byte, 64)
	n, err := unix.Read(fd, buf)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Read failed: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	if !bytes.Equal(buf[:n], testData) {
		fmt.Fprintf(os.Stderr, "read data mismatch: got %q, want %q\n", string(buf[:n]), string(testData))
		unix.Close(fd)
		os.Exit(1)
	}
	unix.Close(fd)

	// 2. unix.Open with O_RDWR | O_CREAT creates a new file with specified permission bits and returns a valid file descriptor
	newFile := filepath.Join(tmpDir, "created.txt")
	fd, err = unix.Open(newFile, unix.O_RDWR|unix.O_CREAT, 0644)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open O_RDWR|O_CREAT failed: %v\n", err)
		os.Exit(1)
	}
	if fd < 0 {
		fmt.Fprintf(os.Stderr, "unix.Open returned negative fd: %d\n", fd)
		os.Exit(1)
	}
	writeData := []byte("created content")
	wn, err := unix.Write(fd, writeData)
	if err != nil || wn != len(writeData) {
		fmt.Fprintf(os.Stderr, "unix.Write failed: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	unix.Close(fd)

	readBack, err := os.ReadFile(newFile)
	if err != nil || !bytes.Equal(readBack, writeData) {
		fmt.Fprintf(os.Stderr, "newFile content mismatch: %v\n", err)
		os.Exit(1)
	}

	// 3. unix.Open with O_CREAT | O_EXCL on an existing file fails with unix.EEXIST error
	fd, err = unix.Open(newFile, unix.O_RDWR|unix.O_CREAT|unix.O_EXCL, 0644)
	if err == nil {
		unix.Close(fd)
		fmt.Fprintf(os.Stderr, "expected EEXIST when opening existing file with O_CREAT|O_EXCL, got success\n")
		os.Exit(1)
	}
	if !errors.Is(err, unix.EEXIST) {
		fmt.Fprintf(os.Stderr, "expected unix.EEXIST, got: %v\n", err)
		os.Exit(1)
	}

	// 4. unix.Open on a non-existent path without O_CREAT fails with unix.ENOENT error
	nonExistent := filepath.Join(tmpDir, "does_not_exist.txt")
	_, err = unix.Open(nonExistent, unix.O_RDONLY, 0)
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected ENOENT for non-existent file, got success\n")
		os.Exit(1)
	}
	if !errors.Is(err, unix.ENOENT) {
		fmt.Fprintf(os.Stderr, "expected unix.ENOENT, got: %v\n", err)
		os.Exit(1)
	}

	// 5. unix.Open with O_WRONLY | O_APPEND writes data at the end of an existing file preserving prior contents
	appendFile := filepath.Join(tmpDir, "append.txt")
	if err := os.WriteFile(appendFile, []byte("prefix-"), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create append test file: %v\n", err)
		os.Exit(1)
	}
	fd, err = unix.Open(appendFile, unix.O_WRONLY|unix.O_APPEND, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open O_APPEND failed: %v\n", err)
		os.Exit(1)
	}
	if _, err := unix.Write(fd, []byte("suffix")); err != nil {
		fmt.Fprintf(os.Stderr, "unix.Write in append mode failed: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	unix.Close(fd)

	appendResult, err := os.ReadFile(appendFile)
	if err != nil || string(appendResult) != "prefix-suffix" {
		fmt.Fprintf(os.Stderr, "append result mismatch: got %q, want %q\n", string(appendResult), "prefix-suffix")
		os.Exit(1)
	}

	// 6. unix.Open with O_WRONLY | O_TRUNC truncates an existing file to zero length on open
	truncFile := filepath.Join(tmpDir, "trunc.txt")
	if err := os.WriteFile(truncFile, []byte("long content that should be truncated away"), 0644); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create trunc test file: %v\n", err)
		os.Exit(1)
	}
	fd, err = unix.Open(truncFile, unix.O_WRONLY|unix.O_TRUNC, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open O_TRUNC failed: %v\n", err)
		os.Exit(1)
	}
	if _, err := unix.Write(fd, []byte("short")); err != nil {
		fmt.Fprintf(os.Stderr, "unix.Write after truncate failed: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	unix.Close(fd)

	truncResult, err := os.ReadFile(truncFile)
	if err != nil || string(truncResult) != "short" {
		fmt.Fprintf(os.Stderr, "trunc result mismatch: got %q, want %q\n", string(truncResult), "short")
		os.Exit(1)
	}

	// 7. unix.Open with O_CLOEXEC sets the close-on-exec flag on the opened file descriptor
	fd, err = unix.Open(existingFile, unix.O_RDONLY|unix.O_CLOEXEC, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Open O_CLOEXEC failed: %v\n", err)
		os.Exit(1)
	}
	val, err := unix.FcntlInt(uintptr(fd), unix.F_GETFD, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.FcntlInt F_GETFD failed: %v\n", err)
		unix.Close(fd)
		os.Exit(1)
	}
	if (val & unix.FD_CLOEXEC) == 0 {
		fmt.Fprintf(os.Stderr, "expected FD_CLOEXEC flag to be set, got flags %d\n", val)
		unix.Close(fd)
		os.Exit(1)
	}
	unix.Close(fd)

	fmt.Println("All contract assertions passed.")
}