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

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.EPERM 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.EPERM

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:e06143ab3802b2b2b227bc2472663250ef025beb5e94e9f20462a787063d5c51","contract":["unix.EPERM represents errno 1 with error string \"operation not permitted\"","unix.Link on a directory returns unix.EPERM","errors.Is matches unix.EPERM with syscall.EPERM","unix.EPERM reports false for Temporary and Timeout error methods","errors.Is accurately identifies unix.EPERM from failed syscall errors"],"goal":"verify golang.org/x/sys/unix.EPERM 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.EPERM"]},"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.EPERM"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

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"
	"path/filepath"

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

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

	// Creating a hard link to a directory is forbidden by the operating system and fails with unix.EPERM
	tmpDir, err := os.MkdirTemp("", "eperm_demo_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	subDir := filepath.Join(tmpDir, "source_dir")
	if err := os.Mkdir(subDir, 0755); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create sub dir: %v\n", err)
		os.Exit(1)
	}

	linkPath := filepath.Join(tmpDir, "dir_link")
	err = unix.Link(subDir, linkPath)
	if errors.Is(err, unix.EPERM) {
		fmt.Println("Successfully detected unix.EPERM from invalid link syscall on directory")
	} else {
		fmt.Fprintf(os.Stderr, "expected unix.EPERM, got: %v\n", err)
		os.Exit(1)
	}
}

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

package main

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"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.EPERM represents errno 1 with error string "operation not permitted"
	if uintptr(unix.EPERM) != 1 {
		return fmt.Errorf("expected unix.EPERM to be 1, got %d", uintptr(unix.EPERM))
	}
	if unix.EPERM.Error() != "operation not permitted" {
		return fmt.Errorf("expected error string 'operation not permitted', got %q", unix.EPERM.Error())
	}

	// 2. unix.Link on a directory returns unix.EPERM
	tmpDir, err := os.MkdirTemp("", "eperm_contract_*")
	if err != nil {
		return fmt.Errorf("failed to create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	sourceDir := filepath.Join(tmpDir, "source_dir")
	if err := os.Mkdir(sourceDir, 0755); err != nil {
		return fmt.Errorf("failed to create source dir: %w", err)
	}

	destLink := filepath.Join(tmpDir, "dest_link")
	linkErr := unix.Link(sourceDir, destLink)
	if linkErr == nil {
		return fmt.Errorf("expected unix.Link on directory to fail, but got nil")
	}
	if !errors.Is(linkErr, unix.EPERM) {
		return fmt.Errorf("expected unix.Link error to match unix.EPERM, got %v", linkErr)
	}

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

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

	// 5. errors.Is accurately identifies unix.EPERM from failed syscall errors
	if !errors.Is(linkErr, unix.Errno(1)) {
		return fmt.Errorf("expected errors.Is(linkErr, unix.Errno(1)) to be true, got false")
	}

	return nil
}