CC-301f · Module 2

Log File Analysis

3 min read

Log files are the archaeological record of what your application did. Claude Code analyzes logs effectively because it can process large volumes of text and identify patterns that a human scanning line-by-line would miss. The approach: feed Claude a relevant slice of the log (not the entire 500MB file — the section around the time of the error) and ask for pattern analysis.

The prompt pattern matters. "Analyze this log file" is vague and produces vague results. "Find all ERROR and WARN entries in this log, group them by error type, and identify any pattern in timing or frequency" produces structured, actionable analysis. "The application crashed at 14:32 UTC. Show me all log entries from 14:25 to 14:35, identify the sequence of events that led to the crash, and highlight any anomalies" produces a timeline-based diagnosis.

Do This

  • Slice logs to a relevant time window before feeding to Claude
  • Ask for specific patterns: error frequency, timing correlations, cascading failures
  • Have Claude build a timeline of events leading to the failure
  • Use Claude to correlate logs across multiple services

Avoid This

  • Feed Claude a 500MB log file and say "find the bug"
  • Ask for generic "analysis" without specifying what you are looking for
  • Ignore log levels — ERROR, WARN, INFO, DEBUG have different diagnostic value
  • Analyze logs from the wrong time window — correlate with the incident timestamp first