Verify Cron Output: Validate Script Results

Your cron runs but the output is wrong or empty? Learn how to verify script output with payload validation and get alerts when results fail—Bash, Python, Node examples.

The Problem: Output Validation

Scripts can run successfully but produce wrong or missing output:

Database query returns empty result set instead of expected data
API call succeeds but response doesn't contain required fields
File processing completes but output file is missing expected content
Report generation runs but produces empty or malformed output
Data transformation completes but output format is wrong
Log parsing succeeds but doesn't find expected patterns

Exit code alone doesn't verify output quality. You need to check output content.

Solution: Validate Output Content

After running your script, verify the output contains expected content. Check for required strings, validate JSON structure, verify file contents, or count output lines. The validation must be inside your script, not in the cron line.

Bash Example: Check Output Contains Expected String

#!/bin/bash
OUTPUT=$(./generate-report.sh)
# Get output validation data
HAS_EXPECTED_CONTENT=0
OUTPUT_LENGTH=${#OUTPUT}
if echo "$OUTPUT" | grep -q "Report generated successfully"; then
  HAS_EXPECTED_CONTENT=1
fi
# Single ping with output validation data in payload
# In DeadManPing panel: set validation rules:
#   - "has_expected_content" == 1
#   - "output_length" > 0
# Panel will automatically detect if output is invalid
curl -X POST "https://deadmanping.com/api/ping/report-job?has_expected_content=$HAS_EXPECTED_CONTENT&output_length=$OUTPUT_LENGTH"

Python Example: Validate JSON Output

import subprocess
import json
import requests
result = subprocess.run(['./api-fetch.sh'], capture_output=True, text=True)
output = result.stdout
# Parse output and extract data for payload
is_valid_json = True
has_required_fields = False
data_not_empty = False
try:
  data = json.loads(output)
  required_fields = ['status', 'data', 'timestamp']
  has_required_fields = all(field in data for field in required_fields)
  data_not_empty = bool(data.get('data'))
except json.JSONDecodeError:
  is_valid_json = False
# Single ping with output validation data in payload
# In DeadManPing panel: set validation rules:
#   - "is_valid_json" == True
#   - "has_required_fields" == True
#   - "data_not_empty" == True
# Panel will automatically detect if output is invalid
requests.post(f"https://deadmanping.com/api/ping/api-job?is_valid_json={is_valid_json}&has_required_fields={has_required_fields}&data_not_empty={data_not_empty}")

Node.js Example: Check File Output Content

const { execSync } = require('child_process');
const fs = require('fs');
const https = require('https');
// Run script
execSync('./process-data.sh');
// Get output file data
const outputFile = '/output/processed-data.json';
let fileExists = fs.existsSync(outputFile);
let lineCount = 0;
let hasStatusField = false;
if (fileExists) {
  const content = fs.readFileSync(outputFile, 'utf8');
  lineCount = content.split('\n').length;
  hasStatusField = content.includes('"status": "success"');
}
// Single ping with output data in payload
// In DeadManPing panel: set validation rules:
//   - "file_exists" == true
//   - "line_count" >= 10
//   - "has_status_field" == true
// Panel will automatically detect if output is invalid
https.request(`https://deadmanping.com/api/ping/data-job?file_exists=${fileExists}&line_count=${lineCount}&has_status_field=${hasStatusField}`, { method: 'POST' }).end();

Bash Example: Count Output Lines

#!/bin/bash
OUTPUT=$(./query-database.sh)
# Count non-empty lines
LINE_COUNT=$(echo "$OUTPUT" | grep -v '^$' | wc -l)
# Single ping with line count in payload
# In DeadManPing panel: set validation rule "line_count" >= 5
# Panel will automatically detect if output has too few lines
curl -X POST "https://deadmanping.com/api/ping/query-job?lines=$LINE_COUNT"

Monitoring Output Validation

After adding output validation to your scripts, use a dead man switch to monitor whether validation completed successfully. If your script detects invalid output and exits with error code, the ping never arrives, and you get an alert.

Include validation details in your ping payload (e.g., line counts, missing fields) so you can track output quality over time.

Working Examples

See complete, working code examples in our GitHub repository:

View Examples on GitHub →

Start Verifying Script Output

DeadManPing monitors whether your output validation completes. Set up monitoring in 2 minutes, get alerts when output is invalid or missing.

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Learn more about cron job monitoring and troubleshooting:

Verify Cron Output: Validate Script Results

The Problem: Output Validation

Solution: Validate Output Content

Bash Example: Check Output Contains Expected String

Python Example: Validate JSON Output

Node.js Example: Check File Output Content

Bash Example: Count Output Lines

Monitoring Output Validation

Working Examples

Start Verifying Script Output

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