Improve test_monitor_tshark.sh output and error handling

- Add progress messages and debug output
- Show tshark warnings/errors
- Always display counters even if no packets captured
- Better handling of empty output
- Show sample packets when available
- Add DLT check before capture

Co-authored-by: Cursor <cursoragent@cursor.com>

test_monitor_tshark.sh

@@ -80,11 +80,32 @@ iw dev "$INTERFACE" info | grep -E "(type|channel)" || echo "Could not verify"
 # Check DLT with tshark (capture for 1 second)
 echo ""
 echo "Checking Data Link Type (1 second test capture)..."
-TEST_OUTPUT=$(timeout 1 tshark -i "$INTERFACE" -T fields -e frame.number -e radiotap.present 2>&1)
+# First check if we can open the interface
+DLT_CHECK=$(tshark -i "$INTERFACE" -T fields -e frame.number -c 0 2>&1 | head -1)
+if echo "$DLT_CHECK" | grep -q "Running as"; then
+    echo "$DLT_CHECK"
+fi
+
+# Use -c to limit packets and add immediate output, redirect stderr to see warnings
+# Use a shorter timeout and limit packets to avoid hanging
+TEST_OUTPUT=$(timeout 2 tshark -i "$INTERFACE" -c 100 -T fields -e frame.number -e radiotap.present 2>&1 || echo "")
+TEST_EXIT_CODE=$?
+
+# Show any warnings/errors from tshark
+echo "$TEST_OUTPUT" | grep -E "(Running as|tshark:|Warning|Error)" || true
+
+# Count packets (lines starting with a number)
 PACKET_COUNT=$(echo "$TEST_OUTPUT" | grep -E '^[0-9]+' | wc -l || echo "0")
-PLCP_COUNT=$(echo "$TEST_OUTPUT" | grep -E '^[0-9]+.*[0-9]' | wc -l || echo "0")
+# Count lines with both frame.number and radiotap.present (non-empty second field)
-echo "$TEST_OUTPUT" | tail -5 || true
+PLCP_COUNT=$(echo "$TEST_OUTPUT" | awk -F'\t' 'NF >= 2 && $1 != "" && $2 != "" && $2 != "0" && $2 != "-" {count++} END {print count+0}' || echo "0")
-echo "Captured $PACKET_COUNT packet(s) in 1 second"
+
+# Show sample output
+if [ "$PACKET_COUNT" -gt 0 ]; then
+    echo "Sample packets:"
+    echo "$TEST_OUTPUT" | grep -E '^[0-9]+' | head -3
+fi
+
+echo "Captured $PACKET_COUNT packet(s) in test capture"
 if [ "$PLCP_COUNT" -gt 0 ]; then
     echo "PLCP headers: $PLCP_COUNT (radiotap present)"
 else
@@ -97,6 +118,7 @@ echo "Press Ctrl+C to stop early"
 echo ""
 
 # Capture for specified duration and count packets
+echo "Capturing packets for $DURATION seconds..."
 CAPTURE_OUTPUT=$(timeout "$DURATION" tshark -i "$INTERFACE" -n -T fields \
     -e frame.number \
     -e frame.time \
@@ -107,16 +129,28 @@ CAPTURE_OUTPUT=$(timeout "$DURATION" tshark -i "$INTERFACE" -n -T fields \
     -e wlan.fc.type_subtype \
     -e radiotap.present \
     2>&1)
+CAPTURE_EXIT_CODE=$?
 
-# Display first 50 lines of output
+# Show any warnings/errors
-echo "$CAPTURE_OUTPUT" | head -50
+echo "$CAPTURE_OUTPUT" | grep -E "(tshark:|Warning|Error)" | head -5 || true
 
-# Count total packets captured
+# Display first 50 lines of packet output
+PACKET_LINES=$(echo "$CAPTURE_OUTPUT" | grep -E '^[0-9]+' || true)
+if [ -n "$PACKET_LINES" ]; then
+    echo ""
+    echo "Sample packets (first 20):"
+    echo "$PACKET_LINES" | head -20
+else
+    echo ""
+    echo "(No packets captured)"
+fi
+
+# Count total packets captured (lines starting with a number)
 FINAL_COUNT=$(echo "$CAPTURE_OUTPUT" | grep -E '^[0-9]+' | wc -l || echo "0")
 
 # Count packets with PLCP headers (radiotap present)
 # radiotap.present field is the 8th field (after frame.number, frame.time, wlan.sa, wlan.da, wlan.fc.type, wlan.fc.subtype, wlan.fc.type_subtype)
-PLCP_COUNT=$(echo "$CAPTURE_OUTPUT" | awk -F'\t' 'NF >= 8 && $8 != "" && $8 != "0" && $8 != "-" {count++} END {print count+0}' || echo "0")
+PLCP_COUNT=$(echo "$CAPTURE_OUTPUT" | awk -F'\t' 'NF >= 8 && $1 != "" && $8 != "" && $8 != "0" && $8 != "-" {count++} END {print count+0}' || echo "0")
 
 echo ""
 echo "=== Capture complete ==="