log line
also: log entry, log record
A single line of text written to a log file, typically containing a timestamp, source identifier, and a message describing an event or action in a system or application.
A log line is the basic unit of logging—one human-readable (or machine-readable) record that captures what happened at a specific moment in time. Each line usually follows a consistent format established by the application or service generating it.
Typical log lines include components like: timestamp, hostname, process name or ID, severity level (INFO, WARNING, ERROR), and the actual message. For example, an Apache web server might log: 192.168.1.100 - - [01/Jan/2024:12:34:56 +0000] "GET /index.html HTTP/1.1" 200 1234
Log lines are aggregated into log files (stored in directories like /var/log/) and are essential for troubleshooting, auditing, and monitoring system health. Tools like grep, tail, and journalctl help you search, filter, and analyze individual log lines or groups of them.