golang.org/x/sys v0.41.0: unix.Rlimit

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.Rlimit in pkg:golang/golang.org/x/sys@v0.41.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.41.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Rlimit

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:ba884b7ae8832586f6b03636b55ce8054408e14e5d06b44f8e8084c85f10de70","contract":["unix.Rlimit defines Cur and Max fields for soft and hard resource boundaries","unix.Getrlimit populates an Rlimit struct with non-zero file descriptor limits for RLIMIT_NOFILE","unix.Getrlimit returns an Rlimit where soft limit Cur does not exceed hard limit Max","unix.Setrlimit updates Cur soft limit within Max hard limit bound and restores original Rlimit","unix.Setrlimit returns EINVAL when Rlimit Cur exceeds Max hard limit"],"goal":"verify golang.org/x/sys/unix.Rlimit in pkg:golang/golang.org/x/sys@v0.41.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.41.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Rlimit"]},"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@v0.41.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.41.0","symbols":["golang.org/x/sys/unix.Rlimit"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require golang.org/x/sys v0.41.0

golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=

package main

import (
	"fmt"
	"os"

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

func main() {
	var rlim unix.Rlimit
	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &rlim); err != nil {
		fmt.Fprintf(os.Stderr, "failed to get RLIMIT_NOFILE: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("RLIMIT_NOFILE: Cur=%d, Max=%d\n", rlim.Cur, rlim.Max)

	customLimit := unix.Rlimit{
		Cur: rlim.Cur,
		Max: rlim.Max,
	}

	fmt.Printf("Custom Rlimit: Cur=%d, Max=%d\n", customLimit.Cur, customLimit.Max)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Rlimit in pkg:golang/golang.org/x/sys@v0.41.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.41.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Rlimit"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

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

func main() {
	// 1. unix.Rlimit defines Cur and Max fields for soft and hard resource boundaries
	custom := unix.Rlimit{
		Cur: 1024,
		Max: 2048,
	}
	if custom.Cur != 1024 || custom.Max != 2048 {
		fmt.Fprintf(os.Stderr, "expected Cur=1024, Max=2048, got Cur=%d, Max=%d\n", custom.Cur, custom.Max)
		os.Exit(1)
	}

	// 2. unix.Getrlimit populates an Rlimit struct with non-zero file descriptor limits for RLIMIT_NOFILE
	var orig unix.Rlimit
	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &orig); err != nil {
		fmt.Fprintf(os.Stderr, "Getrlimit(RLIMIT_NOFILE) failed: %v\n", err)
		os.Exit(1)
	}
	if orig.Cur == 0 || orig.Max == 0 {
		fmt.Fprintf(os.Stderr, "expected non-zero limits, got Cur=%d, Max=%d\n", orig.Cur, orig.Max)
		os.Exit(1)
	}

	// 3. unix.Getrlimit returns an Rlimit where soft limit Cur does not exceed hard limit Max
	if orig.Cur > orig.Max {
		fmt.Fprintf(os.Stderr, "expected Cur <= Max, got Cur=%d, Max=%d\n", orig.Cur, orig.Max)
		os.Exit(1)
	}

	// 4. unix.Setrlimit updates Cur soft limit within Max hard limit bound and restores original Rlimit
	targetCur := orig.Cur
	if targetCur > 100 {
		targetCur = targetCur - 1
	}
	newLim := unix.Rlimit{
		Cur: targetCur,
		Max: orig.Max,
	}
	if err := unix.Setrlimit(unix.RLIMIT_NOFILE, &newLim); err != nil {
		fmt.Fprintf(os.Stderr, "Setrlimit failed to set Cur to %d: %v\n", targetCur, err)
		os.Exit(1)
	}

	var verified unix.Rlimit
	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &verified); err != nil {
		fmt.Fprintf(os.Stderr, "Getrlimit failed after Setrlimit: %v\n", err)
		os.Exit(1)
	}
	if verified.Cur != targetCur {
		fmt.Fprintf(os.Stderr, "expected updated Cur=%d, got %d\n", targetCur, verified.Cur)
		os.Exit(1)
	}

	// Restore original limits
	if err := unix.Setrlimit(unix.RLIMIT_NOFILE, &orig); err != nil {
		fmt.Fprintf(os.Stderr, "failed to restore original limits: %v\n", err)
		os.Exit(1)
	}
	var restored unix.Rlimit
	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &restored); err != nil {
		fmt.Fprintf(os.Stderr, "Getrlimit failed after restoring limits: %v\n", err)
		os.Exit(1)
	}
	if restored.Cur != orig.Cur || restored.Max != orig.Max {
		fmt.Fprintf(os.Stderr, "limits not restored correctly: got Cur=%d, Max=%d, expected Cur=%d, Max=%d\n",
			restored.Cur, restored.Max, orig.Cur, orig.Max)
		os.Exit(1)
	}

	// 5. unix.Setrlimit returns EINVAL when Rlimit Cur exceeds Max hard limit
	invalidLim := unix.Rlimit{
		Cur: 2048,
		Max: 1024,
	}
	err := unix.Setrlimit(unix.RLIMIT_NOFILE, &invalidLim)
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected error when Cur > Max, got nil\n")
		os.Exit(1)
	}
	if !errors.Is(err, unix.EINVAL) {
		fmt.Fprintf(os.Stderr, "expected EINVAL when Cur > Max, got: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed successfully.")
}