# Interface Matching Guide
bandwidthmon supports flexible interface matching to make it easier to specify network interfaces.
## How Interface Matching Works
### 1. Exact Match (Highest Priority)
If the pattern exactly matches an interface name, it will be selected:
```bash
# Windows
bandwidthmon -i "vEthernet (realtek)"
# Linux
bandwidthmon -i eth0
bandwidthmon -i wlan0
# macOS
bandwidthmon -i en0
```
### 2. Partial Match (Case-Insensitive)
If no exact match is found, bandwidthmon searches for interfaces containing the pattern (case-insensitive):
```bash
# These will match "vEthernet (realtek)":
bandwidthmon -i realtek # ✓ matches
bandwidthmon -i Real # ✓ matches
bandwidthmon -i REALTEK # ✓ matches
bandwidthmon -i veth # ✓ matches
# These will match "Ethernet (eth0)":
bandwidthmon -i eth # ✓ matches
bandwidthmon -i Ether # ✓ matches
```
### 3. Multiple Matches
If multiple interfaces match the pattern, bandwidthmon automatically selects the **shortest** interface name (most specific):
```bash
# If you have:
# - "Ethernet (eth0)-WFP Native MAC Layer LightWeight Filter-0000"
# - "Ethernet (eth0)"
# - "vEthernet (realtek)"
bandwidthmon -i eth
# Will select: "Ethernet (eth0)" (shortest match)
bandwidthmon -i realtek
# Will select: "vEthernet (realtek)" (only match)
```
## Platform-Specific Examples
### Windows
Windows interface names are often verbose:
```bash
# List interfaces first
bandwidthmon -l
# Output might show:
# - Ethernet (eth0)-WFP Native MAC Layer LightWeight Filter-0000
# - Ethernet (eth0)
# - vEthernet (realtek)
# - WiFi
# Quick matching:
bandwidthmon -i eth # Matches "Ethernet (eth0)"
bandwidthmon -i realtek # Matches "vEthernet (realtek)"
bandwidthmon -i wifi # Matches "WiFi"
```
### Linux
Linux interfaces have simpler names:
```bash
# List interfaces
bandwidthmon -l
# Output might show:
# - eth0
# - wlan0
# - lo
# - docker0
# Matching (usually exact):
bandwidthmon -i eth0 # Exact match
bandwidthmon -i wlan # Matches "wlan0"
bandwidthmon -i lo # Exact match
```
### macOS
macOS uses en* naming:
```bash
# List interfaces
bandwidthmon -l
# Output might show:
# - en0 (WiFi)
# - en1 (Thunderbolt)
# - lo0
# Matching:
bandwidthmon -i en0 # Exact match
bandwidthmon -i wifi # Matches "en0 (WiFi)"
bandwidthmon -i thunder # Matches "en1 (Thunderbolt)"
```
## Error Messages
### No Match Found
```bash
bandwidthmon -i xyz
# Error output:
Error: No interface matches 'xyz'. Available interfaces:
Ethernet (eth0)
vEthernet (realtek)
WiFi
```
The error message shows all available interfaces to help you choose.
## Best Practices
### 1. List Interfaces First
Always start by listing available interfaces:
```bash
bandwidthmon -l
```
### 2. Use Unique Substrings
Choose the most unique part of the interface name:
```bash
# Good (unique):
bandwidthmon -i realtek
# Less ideal (might match multiple):
bandwidthmon -i eth
```
### 3. Use Quotes for Names with Spaces
```bash
# Windows
bandwidthmon -i "vEthernet (realtek)"
bandwidthmon -i "Ethernet (eth0)"
# Or use partial match without quotes:
bandwidthmon -i realtek
```
### 4. Case Doesn't Matter
```bash
# All equivalent:
bandwidthmon -i REALTEK
bandwidthmon -i realtek
bandwidthmon -i Realtek
```
## Troubleshooting
### Interface Not Found
**Problem:** Getting "Interface not found" error
**Solution:**
1. List all interfaces: `bandwidthmon -l`
2. Find the correct name or unique substring
3. Try partial match with a unique part
**Example:**
```bash
# List interfaces
bandwidthmon -l
# Shows: "vEthernet (realtek)"
# Use partial match
bandwidthmon -i realtek # ✓ Works!
```
### Multiple Matches Warning
**Problem:** Pattern matches multiple interfaces
**Solution:**
The tool automatically selects the shortest name. To be more specific:
1. Use a more unique substring
2. Use the full interface name in quotes
**Example:**
```bash
# If "eth" matches both:
# - "Ethernet (eth0)"
# - "Ethernet (eth0)-WFP Native..."
# Option 1: More specific pattern
bandwidthmon -i "eth0)"
# Option 2: Full name
bandwidthmon -i "Ethernet (eth0)"
```
### Special Characters
**Problem:** Interface name has special characters
**Solution:** Use quotes:
```bash
# Correct:
bandwidthmon -i "vEthernet (realtek)"
# Wrong (shell interprets parentheses):
bandwidthmon -i vEthernet (realtek)
```
## Examples from Your Output
Based on your system's output:
```
Available interfaces:
- Ethernet (eth0)-WFP Native MAC Layer LightWeight Filter-0000
- Ethernet (eth0)
- vEthernet (realtek)
```
### To monitor realtek:
```bash
# Best (most specific):
bandwidthmon -i realtek
# Also works:
bandwidthmon -i "vEthernet (realtek)"
bandwidthmon -i veth
bandwidthmon -i REAL
```
### To monitor eth0:
```bash
# Best (avoids WFP filter):
bandwidthmon -i "Ethernet (eth0)"
# Also works (selects shortest):
bandwidthmon -i eth0
# Works but less specific:
bandwidthmon -i eth
```
## Advanced Usage
### Auto-Select Best Interface
Don't specify any interface to auto-select the one with most traffic:
```bash
bandwidthmon
```
This selects the interface with the highest total bytes (received + transmitted).
### Monitor Specific Interface Types
```bash
# WiFi interfaces
bandwidthmon -i wifi
bandwidthmon -i wlan
# Ethernet interfaces
bandwidthmon -i eth
# Virtual interfaces
bandwidthmon -i veth
bandwidthmon -i docker
# Loopback
bandwidthmon -i lo
```
## Summary
- **Exact match** is tried first
- **Partial match** is case-insensitive
- **Shortest name** wins for multiple matches
- **Use quotes** for names with spaces/special characters
- **List first** with `-l` to see available interfaces
- **Be specific** to avoid ambiguity
For the most reliable results, use the **exact interface name** in quotes!
