How to Debug Partial Cron Job Failures (15 Success, 6 Errors Out of 21)

TL;DR When your automated system shows partial failures (some cron jobs succeed, others fail), you're likely dealing with selective failures rather than systemic infrastructure issues. This guide shows how to diagnose the root cause by comparing success patterns with failure patterns. Prerequisites Linux/macOS environment running cron Multiple cron jobs scheduled for periodic execution Experiencing a pattern where some jobs succeed and some fail The Problem: 15 Out of 21 Jobs Succeed Real-world scenario from production: Status Count Examples Success 15 build-in-public, article-writer, slideshow-en-2 Error 6 larry-trend-hunter-ja, daily-analytics-report, app-metrics-morning Key observations: All EN-side posts (slideshow-en-1/2/3) succeeded JA-side posts (slideshow-ja-1) failed on first run but succeeded on runs 2/3 Analytics-related cron jobs (app-metrics, daily-analytics) consistently failed Step 1: Categorize Success vs Failure # Get today's cron execution history grep "CRON" /var/log