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

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.SEEK_SET 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.SEEK_SET

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:sha256:39be79d2f9c219cee224dfd3e227f4bf79956d8399ce339bba34d68630dcf4a5","contract":["unix.SEEK_SET constant equals integer 0","unix.Seek with unix.SEEK_SET positions the file offset relative to the beginning of the file","unix.Seek with unix.SEEK_SET allows seeking to arbitrary offsets and reading expected contents"],"goal":"verify golang.org/x/sys/unix.SEEK_SET 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.SEEK_SET"]},"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.SEEK_SET"],"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"
	"io"
	"os"

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

func main() {
	tmpFile, err := os.CreateTemp("", "seek_set_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()

	testData := "Hello, CodeSampleX!"
	if _, err := tmpFile.WriteString(testData); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write test data: %v\n", err)
		os.Exit(1)
	}

	newOffset, err := unix.Seek(int(tmpFile.Fd()), 7, unix.SEEK_SET)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Seek failed: %v\n", err)
		os.Exit(1)
	}

	buf := make([]byte, 11)
	n, err := tmpFile.Read(buf)
	if err != nil && err != io.EOF {
		fmt.Fprintf(os.Stderr, "read failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Seek offset: %d\n", newOffset)
	fmt.Printf("Read bytes: %s\n", string(buf[:n]))
}

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

package main

import (
	"bytes"
	"fmt"
	"io"
	"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.SEEK_SET constant equals integer 0
	if unix.SEEK_SET != 0 {
		return fmt.Errorf("expected unix.SEEK_SET to equal 0, got %d", unix.SEEK_SET)
	}

	// Setup temporary file with known content
	tmpFile, err := os.CreateTemp("", "seek_set_contract_*")
	if err != nil {
		return fmt.Errorf("failed to create temporary file: %w", err)
	}
	defer os.Remove(tmpFile.Name())
	defer tmpFile.Close()

	payload := []byte("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ")
	if _, err := tmpFile.Write(payload); err != nil {
		return fmt.Errorf("failed to write payload: %w", err)
	}

	fd := int(tmpFile.Fd())

	// 2. unix.Seek with unix.SEEK_SET positions the file offset relative to the beginning of the file
	off, err := unix.Seek(fd, 0, unix.SEEK_SET)
	if err != nil {
		return fmt.Errorf("unix.Seek to 0 failed: %w", err)
	}
	if off != 0 {
		return fmt.Errorf("expected offset 0, got %d", off)
	}

	off, err = unix.Seek(fd, 10, unix.SEEK_SET)
	if err != nil {
		return fmt.Errorf("unix.Seek to 10 failed: %w", err)
	}
	if off != 10 {
		return fmt.Errorf("expected offset 10, got %d", off)
	}

	// 3. unix.Seek with unix.SEEK_SET allows seeking to arbitrary offsets and reading expected contents
	buf := make([]byte, 5)
	n, err := io.ReadFull(tmpFile, buf)
	if err != nil {
		return fmt.Errorf("failed to read from offset 10: %w", err)
	}
	if n != 5 || !bytes.Equal(buf, []byte("ABCDE")) {
		return fmt.Errorf("expected 'ABCDE' at offset 10, got %q", string(buf[:n]))
	}

	off, err = unix.Seek(fd, 4, unix.SEEK_SET)
	if err != nil {
		return fmt.Errorf("unix.Seek back to 4 failed: %w", err)
	}
	if off != 4 {
		return fmt.Errorf("expected offset 4, got %d", off)
	}

	buf = make([]byte, 4)
	n, err = io.ReadFull(tmpFile, buf)
	if err != nil {
		return fmt.Errorf("failed to read from offset 4: %w", err)
	}
	if n != 4 || !bytes.Equal(buf, []byte("4567")) {
		return fmt.Errorf("expected '4567' at offset 4, got %q", string(buf[:n]))
	}

	return nil
}