logger

Overview

The logger command makes entries in the system log. It provides a shell command interface to the syslog system log module, allowing you to create log entries from the command line or scripts.

Syntax

logger [options] [message]

Common Options

Option Description
-f file Log contents of file
-i Log process ID
-p priority Specify message priority
-t tag Mark every line with specified tag
-n server Write to remote syslog server
-s Output to standard error as well
-u socket Write to specified socket
--id=[id] Enter log entry with specified ID

Key Use Cases

  1. Script logging
  2. System monitoring
  3. Application debugging
  4. Security auditing
  5. Event tracking

Examples with Explanations

Example 1: Basic Logging

logger "System backup completed successfully"

Logs a simple message to syslog

Example 2: Tagged Message

logger -t BACKUP -p local0.info "Backup process started"

Logs a tagged message with priority

Example 3: Log File Contents

logger -f /var/log/myapp.log

Sends file contents to syslog

Understanding Output

Priority Levels: - emerg (0): System is unusable - alert (1): Action must be taken immediately - crit (2): Critical conditions - err (3): Error conditions - warning (4): Warning conditions - notice (5): Normal but significant - info (6): Informational - debug (7): Debug-level messages

Common Usage Patterns

  1. Script logging:

    logger -t myscript -p local0.info "Script started"

  2. Error logging:

    logger -i -t myapp -p local0.err "Error: Database connection failed"

  3. Remote logging:

    logger -n logserver.example.com -P 514 "Remote log entry"

Performance Analysis

  • Minimal system impact
  • Asynchronous operation
  • Consider log rotation
  • Monitor disk usage
  • Check syslog configuration

Additional Resources