Overview of tail
`tail` command is specialized in showing the 'tail' part of a file, that is, the most recently added content. This contrasts with the `head` command, which shows the beginning part of a file. Notably, the `--follow` (or `-f`) option outputs new content added to the file in real-time, making it extremely useful for server log monitoring.
Main Role of tail
`tail` command is mainly used for the following purposes:
Key Use Cases
- Log File Monitoring: Monitor the log files of servers or applications in real-time to detect issues early.
- Check File Changes: Quickly grasp what content has been added by checking the last part of the file.
- Data Streaming: Process data by passing the output of `tail` to other commands through pipelines (`|`).
Key tail Command Options
`tail` command offers various options for specifying the number of lines/bytes to output, real-time monitoring, processing multiple files, and more.
1. Specify Output Range
2. Real-Time Monitoring and File Processing
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Description:
`tail` Executes the command.
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Usage Examples
Learn how to effectively monitor log files and check recent changes to files through various usage examples of the `tail` command.
Check the last 10 lines of a log file
tail /var/log/apache2/access.logOutputs the most recent 10 lines of the Apache web server's access log file `access.log`.
Monitor a log file in real-time
tail -f /var/log/syslogImmediately outputs to the terminal whenever new content is added to the system log file `syslog`. Can be stopped with `Ctrl+C`.
Check the last 50 lines of a specific file
tail -n 50 /var/log/application.logOutputs the most recent 50 lines of the `application.log` file.
Simultaneously monitor multiple log files in real-time
tail -f /var/log/nginx/access.log /var/log/nginx/error.logTracks both `access.log` and `error.log` files in real-time. Each file's output is distinguished by its file name.
Real-time monitoring considering log rotation
tail -F /var/log/messagesTracks the latest logs without interruption even when log files are periodically renamed or newly created (log rotation).
Output from a specific point in a file to the end
tail +100 large_data.txtOutputs all lines from `start_line_number` to the end of the file. You can specify the starting line number using `+`.