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

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.AT_SYMLINK_NOFOLLOW 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.AT_SYMLINK_NOFOLLOW

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:sha256:329b0119bb10373aa1ca9eaab1c29489bb17a5adc09e7c4cf2ada2529e6bd3cf","contract":["unix.AT_SYMLINK_NOFOLLOW constant equals integer 0x100","unix.Fstatat with unix.AT_SYMLINK_NOFOLLOW queries the link itself rather than the target file","unix.Fstatat without unix.AT_SYMLINK_NOFOLLOW follows the symbolic link to the target file"],"goal":"verify golang.org/x/sys/unix.AT_SYMLINK_NOFOLLOW 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.AT_SYMLINK_NOFOLLOW"]},"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.AT_SYMLINK_NOFOLLOW"],"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"
	"path/filepath"

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

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

	targetPath := filepath.Join(tmpDir, "target.txt")
	if err := os.WriteFile(targetPath, []byte("target content"), 0600); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create target file: %v\n", err)
		os.Exit(1)
	}

	symlinkPath := filepath.Join(tmpDir, "link.txt")
	if err := os.Symlink(targetPath, symlinkPath); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create symlink: %v\n", err)
		os.Exit(1)
	}

	var statLink unix.Stat_t
	if err := unix.Fstatat(unix.AT_FDCWD, symlinkPath, &statLink, unix.AT_SYMLINK_NOFOLLOW); err != nil {
		fmt.Fprintf(os.Stderr, "unix.Fstatat with AT_SYMLINK_NOFOLLOW failed: %v\n", err)
		os.Exit(1)
	}

	var statTarget unix.Stat_t
	if err := unix.Fstatat(unix.AT_FDCWD, symlinkPath, &statTarget, 0); err != nil {
		fmt.Fprintf(os.Stderr, "unix.Fstatat without AT_SYMLINK_NOFOLLOW failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("AT_SYMLINK_NOFOLLOW flag: 0x%x\n", unix.AT_SYMLINK_NOFOLLOW)
	fmt.Printf("Symlink mode is symlink: %t\n", (statLink.Mode&unix.S_IFMT) == unix.S_IFLNK)
	fmt.Printf("Target mode is regular file: %t\n", (statTarget.Mode&unix.S_IFMT) == unix.S_IFREG)
}

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

package main

import (
	"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 assertions passed.")
}

func runTests() error {
	// 1. unix.AT_SYMLINK_NOFOLLOW constant equals integer 0x100
	if unix.AT_SYMLINK_NOFOLLOW != 0x100 {
		return fmt.Errorf("expected unix.AT_SYMLINK_NOFOLLOW to equal 0x100, got 0x%x", unix.AT_SYMLINK_NOFOLLOW)
	}

	tmpDir, err := os.MkdirTemp("", "contract_test_*")
	if err != nil {
		return fmt.Errorf("failed to create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	targetPath := filepath.Join(tmpDir, "target.txt")
	if err := os.WriteFile(targetPath, []byte("target file data"), 0600); err != nil {
		return fmt.Errorf("failed to write target file: %w", err)
	}

	symlinkPath := filepath.Join(tmpDir, "symlink.txt")
	if err := os.Symlink(targetPath, symlinkPath); err != nil {
		return fmt.Errorf("failed to create symlink: %w", err)
	}

	// 2. unix.Fstatat with unix.AT_SYMLINK_NOFOLLOW queries the link itself rather than the target file
	var statLink unix.Stat_t
	if err := unix.Fstatat(unix.AT_FDCWD, symlinkPath, &statLink, unix.AT_SYMLINK_NOFOLLOW); err != nil {
		return fmt.Errorf("unix.Fstatat with AT_SYMLINK_NOFOLLOW failed: %w", err)
	}
	if (statLink.Mode & unix.S_IFMT) != unix.S_IFLNK {
		return fmt.Errorf("expected S_IFLNK mode for symlink with AT_SYMLINK_NOFOLLOW, got 0%o", statLink.Mode&unix.S_IFMT)
	}

	// 3. unix.Fstatat without unix.AT_SYMLINK_NOFOLLOW follows the symbolic link to the target file
	var statTarget unix.Stat_t
	if err := unix.Fstatat(unix.AT_FDCWD, symlinkPath, &statTarget, 0); err != nil {
		return fmt.Errorf("unix.Fstatat without AT_SYMLINK_NOFOLLOW failed: %w", err)
	}
	if (statTarget.Mode & unix.S_IFMT) != unix.S_IFREG {
		return fmt.Errorf("expected S_IFREG mode for target file without AT_SYMLINK_NOFOLLOW, got 0%o", statTarget.Mode&unix.S_IFMT)
	}

	// Verify inode numbers: symlink inode should differ from target file inode
	if statLink.Ino == statTarget.Ino {
		return fmt.Errorf("expected different inode numbers for symlink and target, got %d for both", statLink.Ino)
	}

	return nil
}