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The net module provides comprehensive networking utilities for checking connectivity, working with IP addresses, performing DNS queries, and making HTTP requests.
Different functions require different tools (curl/wget, nc, dig/nslookup). Functions gracefully degrade and provide helpful error messages when tools are missing.

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Connectivity

Functions for testing network connectivity.
Check if the system has internet connectivity.
net::is_online && echo "Connected to internet"
Tries multiple DNS endpoints (8.8.8.8, 1.1.1.1, 9.9.9.9) for reliability.Returns: Exit code 0 if online
Check if a specific host is reachable.
net::can_reach "github.com" && echo "GitHub is reachable"
net::can_reach "internal.server" 5  # 5 second timeout
Parameters:
  • host - Hostname or IP address
  • timeout - Timeout in seconds (default: 2)
Returns: Exit code 0 if reachable
Ping a host and return average round-trip time.
latency=$(net::ping "google.com")
echo "Latency: ${latency}ms"

latency=$(net::ping "server.local" 10)
Parameters:
  • host - Hostname or IP address
  • count - Number of pings (default: 4)
Returns: Average RTT in milliseconds

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Port operations

Functions for checking and scanning ports.
Check if a TCP port is open.
net::port::is_open "localhost" 8080 && echo "Server is running"
net::port::is_open "192.168.1.1" 22 1  # Quick check with 1s timeout
Uses nc if available, falls back to pure bash /dev/tcp trick.Parameters:
  • host - Hostname or IP address
  • port - Port number
  • timeout - Timeout in seconds (default: 2)
Returns: Exit code 0 if port is open
Wait until a port is open (useful for service readiness).
# Wait for database to be ready
if net::port::wait "localhost" 5432 30; then
    echo "Database is ready"
else
    echo "Database failed to start within 30 seconds"
fi
Parameters:
  • host - Hostname or IP address
  • port - Port number
  • timeout - Maximum wait time in seconds (default: 30)
  • interval - Check interval in seconds (default: 1)
Returns: Exit code 0 if port opens within timeout
Scan a range of ports and print open ones.
# Scan common ports
net::port::scan "localhost" 1 1024

# Scan specific range
net::port::scan "192.168.1.1" 8000 9000
Parameters:
  • host - Hostname or IP address
  • start_port - First port to scan (default: 1)
  • end_port - Last port to scan (default: 1024)
Returns: List of open ports (one per line)
Scanning large port ranges can be slow. Use responsibly.

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IP address operations

Functions for working with IP addresses.
Get the local IP address (first non-loopback).
ip=$(net::ip::local)
echo "Local IP: $ip"
Uses ip command if available, falls back to ifconfig.Returns: Local IP address
Get the public IP address.
public=$(net::ip::public)
echo "Public IP: $public"
Tries multiple services with fallback: ipify.org, ifconfig.me, icanhazip.com, checkip.amazonaws.com.Returns: Public IP address
Get all local IP addresses.
net::ip::all
# 192.168.1.100
# 10.0.0.5
# 172.17.0.1
Returns: All local IPs (one per line)
Check if a string is a valid IPv4 address.
net::ip::is_valid_v4 "192.168.1.1" && echo "Valid IPv4"
net::ip::is_valid_v4 "999.999.999.999" || echo "Invalid"
Validates both format and octet ranges (0-255).Parameters:
  • ip - IP address string to validate
Returns: Exit code 0 if valid IPv4
Check if a string is a valid IPv6 address (basic check).
net::ip::is_valid_v6 "2001:0db8::1" && echo "Valid IPv6"
Parameters:
  • ip - IP address string to validate
Returns: Exit code 0 if valid IPv6 format
Check if an IP is in a private range.
net::ip::is_private "192.168.1.1" && echo "Private IP"
net::ip::is_private "8.8.8.8" || echo "Public IP"
Checks for 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.Parameters:
  • ip - IPv4 address
Returns: Exit code 0 if private
Check if an IP is a loopback address.
net::ip::is_loopback "127.0.0.1" && echo "Loopback"
net::ip::is_loopback "::1" && echo "IPv6 loopback"
Parameters:
  • ip - IP address
Returns: Exit code 0 if loopback

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DNS operations

Functions for DNS queries and hostname resolution.
Get the system hostname.
host=$(net::hostname)
echo "Hostname: $host"
Returns: System hostname
Get the fully qualified domain name.
fqdn=$(net::hostname::fqdn)
echo "FQDN: $fqdn"
Returns: Fully qualified domain name
Resolve hostname to IP address.
ip=$(net::resolve "github.com")
echo "GitHub IP: $ip"
Tries dig, nslookup, getent, then ping for maximum compatibility.Parameters:
  • hostname - Hostname to resolve
Returns: IP address
Reverse DNS lookup — IP to hostname.
hostname=$(net::resolve::reverse "8.8.8.8")
echo "$hostname"  # dns.google
Parameters:
  • ip - IP address
Returns: Hostname
Get DNS records of a specific type.
net::dns::records "example.com" A
net::dns::records "example.com" AAAA
net::dns::records "example.com" CNAME
Parameters:
  • hostname - Domain name
  • type - Record type (default: A)
Returns: DNS records
Get MX (mail) records.
net::dns::mx "gmail.com"
Parameters:
  • domain - Domain name
Returns: MX records with priority
Get TXT records (SPF, DKIM, etc.).
net::dns::txt "example.com"
Parameters:
  • domain - Domain name
Returns: TXT records
Get nameserver records.
net::dns::ns "example.com"
Parameters:
  • domain - Domain name
Returns: NS records
Check DNS propagation across multiple public resolvers.
net::dns::propagation "example.com"
# Google       93.184.216.34
# Cloudflare   93.184.216.34
# Quad9        93.184.216.34
# OpenDNS      93.184.216.34
Queries Google (8.8.8.8), Cloudflare (1.1.1.1), Quad9 (9.9.9.9), and OpenDNS.Parameters:
  • hostname - Domain name to check
Returns: Formatted list of results from each resolver
Useful for verifying DNS changes have propagated globally.

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Usage example

source compiled.sh

# Check internet connectivity
if net::is_online; then
    echo "Internet connection: OK"
    
    # Get IP addresses
    local_ip=$(net::ip::local)
    public_ip=$(net::ip::public)
    echo "Local IP: $local_ip"
    echo "Public IP: $public_ip"
    
    # Check if IP is private
    if net::ip::is_private "$local_ip"; then
        echo "Using private network"
    fi
    
    # DNS lookup
    github_ip=$(net::resolve "github.com")
    echo "GitHub resolves to: $github_ip"
    
    # Check if service is available
    if net::port::is_open "github.com" 443; then
        echo "GitHub HTTPS is accessible"
    fi
else
    echo "No internet connection"
fi

# Wait for local service to start
echo "Starting database..."
if net::port::wait "localhost" 5432 30; then
    echo "Database is ready"
else
    echo "Database failed to start"
    exit 1
fi

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