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

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.EACCES 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.EACCES

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:c16d91ecde30c8ca9aab2ad0d94820f6da14603de3c5da9e11a231f8febb6382","contract":["unix.EACCES represents errno 13 with error string \"permission denied\"","unix.Access with X_OK on a non-executable file returns unix.EACCES","errors.Is matches unix.EACCES with syscall.EACCES","unix.EACCES reports false for Temporary and Timeout error methods","errors.Is accurately identifies unix.EACCES from failed syscall errors"],"goal":"verify golang.org/x/sys/unix.EACCES 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.EACCES"]},"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.EACCES"],"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 (
	"errors"
	"fmt"
	"os"
	"syscall"

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

func main() {
	fmt.Printf("POSIX EACCES Errno: %d (%s)\n", int(unix.EACCES), unix.EACCES.Error())

	tmpFile, err := os.CreateTemp("", "eacces_demo_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(tmpFile.Name())

	if err := tmpFile.Chmod(0644); err != nil {
		tmpFile.Close()
		fmt.Fprintf(os.Stderr, "failed to chmod: %v\n", err)
		os.Exit(1)
	}
	tmpFile.Close()

	// Access with X_OK on non-executable file returns unix.EACCES
	err = unix.Access(tmpFile.Name(), unix.X_OK)
	if errors.Is(err, unix.EACCES) {
		fmt.Println("Successfully detected unix.EACCES from execute access check on non-executable file")
	} else {
		fmt.Fprintf(os.Stderr, "expected unix.EACCES, got: %v\n", err)
		os.Exit(1)
	}

	if errors.Is(unix.EACCES, syscall.EACCES) {
		fmt.Println("unix.EACCES correctly matches syscall.EACCES")
	}
}

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

package main

import (
	"errors"
	"fmt"
	"os"
	"syscall"

	"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.EACCES represents errno 13 with error string "permission denied"
	if uintptr(unix.EACCES) != 13 {
		return fmt.Errorf("expected unix.EACCES to be 13, got %d", uintptr(unix.EACCES))
	}
	if unix.EACCES.Error() != "permission denied" {
		return fmt.Errorf("expected error string 'permission denied', got %q", unix.EACCES.Error())
	}

	// 2. unix.Access with X_OK on a non-executable file returns unix.EACCES
	tmpFile, err := os.CreateTemp("", "eacces_contract_*")
	if err != nil {
		return fmt.Errorf("failed to create temp file: %w", err)
	}
	defer os.Remove(tmpFile.Name())

	if err := tmpFile.Chmod(0644); err != nil {
		tmpFile.Close()
		return fmt.Errorf("failed to chmod temp file: %w", err)
	}
	tmpFile.Close()

	accessErr := unix.Access(tmpFile.Name(), unix.X_OK)
	if accessErr == nil {
		return fmt.Errorf("expected unix.Access with X_OK to fail on non-executable file, but succeeded")
	}
	if !errors.Is(accessErr, unix.EACCES) {
		return fmt.Errorf("expected unix.Access error to match unix.EACCES, got %v", accessErr)
	}

	// Also verify read-only file write access if non-root
	if os.Geteuid() != 0 {
		readOnlyFile, err := os.CreateTemp("", "eacces_ro_*")
		if err != nil {
			return fmt.Errorf("failed to create temp file: %w", err)
		}
		defer os.Remove(readOnlyFile.Name())
		if err := readOnlyFile.Chmod(0400); err != nil {
			readOnlyFile.Close()
			return fmt.Errorf("failed to chmod: %w", err)
		}
		readOnlyFile.Close()

		openFd, openErr := unix.Open(readOnlyFile.Name(), unix.O_WRONLY, 0)
		if openErr == nil {
			unix.Close(openFd)
			return fmt.Errorf("expected unix.Open to fail with EACCES, got nil")
		}
		if !errors.Is(openErr, unix.EACCES) {
			return fmt.Errorf("expected unix.Open error to match unix.EACCES, got %v", openErr)
		}
	}

	// 3. errors.Is matches unix.EACCES with syscall.EACCES
	if !errors.Is(unix.EACCES, syscall.EACCES) {
		return fmt.Errorf("expected errors.Is(unix.EACCES, syscall.EACCES) to be true")
	}
	if !errors.Is(syscall.EACCES, unix.EACCES) {
		return fmt.Errorf("expected errors.Is(syscall.EACCES, unix.EACCES) to be true")
	}
	if syscall.Errno(unix.EACCES) != syscall.EACCES {
		return fmt.Errorf("expected syscall.Errno(unix.EACCES) == syscall.EACCES")
	}

	// 4. unix.EACCES reports false for Temporary and Timeout error methods
	if unix.EACCES.Temporary() {
		return fmt.Errorf("expected unix.EACCES.Temporary() to be false")
	}
	if unix.EACCES.Timeout() {
		return fmt.Errorf("expected unix.EACCES.Timeout() to be false")
	}

	// 5. errors.Is accurately identifies unix.EACCES from failed syscall errors
	if !errors.Is(accessErr, unix.Errno(13)) {
		return fmt.Errorf("expected errors.Is(accessErr, unix.Errno(13)) to be true, got false")
	}

	return nil
}