You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: iptables.go
    path of file: ./repos/sliver/vendor/tailscale.com/util/linuxfw
    
    the code of the file until where you have to start completion: // Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

// TODO(#8502): add support for more architectures
//go:build linux && (arm64 || amd64)

package linuxfw

import (
	"fmt"
	"os/exec"
	"strings"
	"unicode"

	"tailscale.com/types/logger"
	"tailscale.com/util/multierr"
)

// DebugNetfilter prints debug information about iptables rules to the
// provided log function.
func DebugIptables(logf logger.Logf) error {
	// unused.
	return nil
}

// detectIptables returns the number of iptables rules that are present in the
// system, ignoring the default "ACCEPT" rule present in the standard iptables
// chains.
//
// It only returns an error when there is no iptables binary, or when iptables -S
// fails. In all other cases, it returns the number of non-default rules.
func detectIptables() (int, error) {
	// run "iptables -S" to get the list of rules using iptables
	// exec.Command returns an error if the binary is not found
	cmd := exec.Command("iptables", "-S")
	output, err := cmd.Output()
	ip6cmd := exec.Command("ip6tables", "-S")
	ip6output, ip6err := ip6cmd.Output()
	var allLines []string
	outputS
    
func detectIptables() (int, error) {
	// run "iptables -S" to get the list of rules using iptables
	// exec.Command returns an error if the binary is not found
	cmd := exec.Command("iptables", "-S")
	output, err := cmd.Output()
	ip6cmd := exec.Command("ip6tables", "-S")
	ip6output, ip6err := ip6cmd.Output()
	var allLines []string
	outputStr := string(output)
	lines := strings.Split(outputStr, "\n")
	ip6outputStr := string(ip6output)
	ip6lines := strings.Split(ip6outputStr, "\n")
	switch {
	case err == nil && ip6err == nil:
		allLines = append(lines, ip6lines...)
	case err == nil && ip6err != nil:
		allLines = lines
	case err != nil && ip6err == nil:
		allLines = ip6lines
	default:
		return 0, FWModeNotSupportedError{
			Mode: FirewallModeIPTables,
			Err:  fmt.Errorf("iptables command run fail: %w", multierr.New(err, ip6err)),
		}
	}

	// count the number of non-default rules
	count := 0
	for _, line := range allLines {
		trimmedLine := strings.TrimLeftFunc(line, unicode.IsSpace)
		if line != "" && strings.HasPrefix(trimmedLine, "-A") {
			// if the line is not empty and starts with "-A", it is a rule appended not default
			count++
		}
	}

	// return the count of non-default rules
	return count, nil
}