golang.org/x/sys v0.23.0: unix.S_IFREG

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.S_IFREG in pkg:golang/golang.org/x/sys@v0.23.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.23.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.S_IFREG

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:sha256:3774c04e88dfee36ca5094d0b389b028293cb603633685272376c69f9d54dbea","contract":["unix.S_IFREG equals octal 0100000 (0x8000) and is preserved under the unix.S_IFMT file-type mask","unix.Stat and unix.Fstat on a regular file report Stat_t.Mode with file-type bits equal to unix.S_IFREG","unix.Stat on a directory and unix.Lstat on a symbolic link do not match unix.S_IFREG under unix.S_IFMT"],"goal":"verify golang.org/x/sys/unix.S_IFREG in pkg:golang/golang.org/x/sys@v0.23.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.23.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.S_IFREG"]},"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@v0.23.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.23.0","symbols":["golang.org/x/sys/unix.S_IFREG"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/sys v0.23.0

golang.org/x/sys v0.23.0 h1:YfKFowiIMvtgl1UERQoTPPToxltDeZfbj4H7dVUCwmM=
golang.org/x/sys v0.23.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

package main

import (
	"fmt"
	"os"

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

func main() {
	f, err := os.CreateTemp("", "regular_check_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "create temp file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(f.Name())
	defer f.Close()

	var st unix.Stat_t
	if err := unix.Stat(f.Name(), &st); err != nil {
		fmt.Fprintf(os.Stderr, "stat temp file: %v\n", err)
		os.Exit(1)
	}

	isRegular := (st.Mode & unix.S_IFMT) == unix.S_IFREG
	fmt.Printf("mode=0%o regular=%t\n", st.Mode, isRegular)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.S_IFREG in pkg:golang/golang.org/x/sys@v0.23.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.23.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.S_IFREG"
  ]
}

package main

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

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

func main() {
	if err := verifyContract(); err != nil {
		fmt.Fprintf(os.Stderr, "contract failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("contract verified")
}

func verifyContract() error {
	// 1. unix.S_IFREG equals octal 0100000 (0x8000) and is preserved under the unix.S_IFMT file-type mask
	if unix.S_IFREG != 0100000 {
		return fmt.Errorf("expected unix.S_IFREG == 0100000, got 0%o", unix.S_IFREG)
	}
	if (unix.S_IFREG & unix.S_IFMT) != unix.S_IFREG {
		return fmt.Errorf("expected (unix.S_IFREG & unix.S_IFMT) == unix.S_IFREG")
	}

	// 2. unix.Stat and unix.Fstat on a regular file report Stat_t.Mode with file-type bits equal to unix.S_IFREG
	dir, err := os.MkdirTemp("", "sifreg_test_*")
	if err != nil {
		return fmt.Errorf("mkdir temp: %w", err)
	}
	defer os.RemoveAll(dir)

	regPath := filepath.Join(dir, "sample.txt")
	f, err := os.OpenFile(regPath, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0600)
	if err != nil {
		return fmt.Errorf("open regular file: %w", err)
	}
	defer f.Close()

	if _, err := f.Write([]byte("sample content")); err != nil {
		return fmt.Errorf("write regular file: %w", err)
	}

	var st unix.Stat_t
	if err := unix.Stat(regPath, &st); err != nil {
		return fmt.Errorf("unix.Stat regular file: %w", err)
	}
	if (st.Mode & unix.S_IFMT) != unix.S_IFREG {
		return fmt.Errorf("unix.Stat mode 0%o did not match unix.S_IFREG", st.Mode)
	}

	var fst unix.Stat_t
	if err := unix.Fstat(int(f.Fd()), &fst); err != nil {
		return fmt.Errorf("unix.Fstat regular file: %w", err)
	}
	if (fst.Mode & unix.S_IFMT) != unix.S_IFREG {
		return fmt.Errorf("unix.Fstat mode 0%o did not match unix.S_IFREG", fst.Mode)
	}

	// 3. unix.Stat on a directory and unix.Lstat on a symbolic link do not match unix.S_IFREG under unix.S_IFMT
	var dirSt unix.Stat_t
	if err := unix.Stat(dir, &dirSt); err != nil {
		return fmt.Errorf("unix.Stat directory: %w", err)
	}
	if (dirSt.Mode & unix.S_IFMT) == unix.S_IFREG {
		return fmt.Errorf("directory mode 0%o unexpectedly matched unix.S_IFREG", dirSt.Mode)
	}

	linkPath := filepath.Join(dir, "sample.link")
	if err := os.Symlink(regPath, linkPath); err != nil {
		return fmt.Errorf("create symlink: %w", err)
	}
	var linkSt unix.Stat_t
	if err := unix.Lstat(linkPath, &linkSt); err != nil {
		return fmt.Errorf("unix.Lstat symlink: %w", err)
	}
	if (linkSt.Mode & unix.S_IFMT) == unix.S_IFREG {
		return fmt.Errorf("symlink Lstat mode 0%o unexpectedly matched unix.S_IFREG", linkSt.Mode)
	}

	return nil
}