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Using Lnav in Shell Scripts for Efficient Log Analysis

Andrios Robert

• 1 min read

Lnav turns raw logs into searchable, structured data without leaving your shell. When combined with shell scripting, it becomes a powerful tool for automated log analysis, filtering, and reporting. This guide covers how to use Lnav in shell scripts to process logs efficiently, integrate with other command-line tools, and automate repetitive tasks.

What is Lnav in Shell Scripting?

Lnav is a console-based log viewer that supports formats like syslog, Apache, and JSON. It can parse logs into tables, run SQL queries directly on them, and pipe results into other programs. In shell scripting, Lnav can be called from scripts to run queries, perform searches, and output reports in plain text or CSV.

Running Lnav from the Command Line

You can feed log files directly into Lnav from a script:

#!/bin/bash
lnav -n -c ":filter-in ERROR" /var/log/syslog

The -n flag disables the curses interface, making output suitable for script parsing. The -c flag runs commands on startup, such as filters or SQL queries.

Using SQL Queries in Scripts

Lnav’s embedded SQLite engine lets you query logs as structured data:

#!/bin/bash
lnav -n -c ";SELECT log_time, log_level, log_msg FROM all_logs WHERE log_level='ERROR'" myapp.log

This allows scripts to extract exact rows and feed them into other pipelines.

Filtering and Exporting Data

Filters remove noise before exporting results:

lnav -n -c ":filter-out DEBUG" -c ":write-to my_errors.csv" myapp.log

This can be embedded in cron jobs to produce daily error reports.

Integrating Lnav with Other Tools

Because Lnav outputs to stdout, you can chain it with grep, awk, or jq. Example:

lnav -n -c ";SELECT * FROM access_log WHERE status=500" apache.log | jq .

This makes it easy to run multi-step processing without manual inspection.

Best Practices for Lnav Shell Scripting

  • Use -n mode for automation.
  • Predefine common queries to avoid duplication.
  • Store log paths in variables for portability.
  • Combine with Unix scheduling for automated monitoring.

Lnav shell scripting reduces log analysis time from hours to seconds. With SQL-powered search, filtered outputs, and staging-ready exports, you get a flexible log processing pipeline right from the shell.

Test this workflow live and see it in action with hoop.dev—connect, run, and watch your Lnav script deliver results in minutes.