tail Command | COMP2041 Week 1

What is tail?什么是tail？

The tail command outputs the last part of files. By default, it shows the last 10 lines. The -f (follow) option is particularly powerful for monitoring log files in real-time as new entries are added.

tail命令输出文件的结尾部分。默认情况下，它显示最后10行。-f（follow）选项对于实时监控日志文件特别有用，因为它可以在添加新条目时持续显示。

Basic Usage基本用法

$ tail file.txt
# Shows last 10 lines (default)
$ tail -n 20 file.txt
# Shows last 20 lines
$ tail -f /var/log/syslog
# Follows the file as it grows (live monitoring)
$ tail file.txt
# 显示最后10行（默认）
$ tail -n 20 file.txt
# 显示最后20行
$ tail -f /var/log/syslog
# 跟踪文件增长（实时监控）

Common Options常用选项

Option选项	Full Name完整名称	Description描述	Example示例
`-n N`	lines行数	Print last N lines打印最后N行	`tail -n 5 file.txt`
`-f`	follow跟踪	Output appended data as file grows文件增长时输出追加的数据	`tail -f logfile.txt`
`-F`	follow=name跟踪名称	Follow even if file is rotated即使文件被轮转也跟踪	`tail -F syslog`
`-n +N`	skip跳过	Start from Nth line to end从第N行开始到末尾	`tail -n +10 file.txt`
`-c N`	bytes字节	Print last N bytes打印最后N字节	`tail -c 100 file.txt`

Practical Scenarios实际场景

Real-time Log Monitoring实时日志监控

$ tail -f /var/log/apache2/access.log
# Monitor web server access logs in real-time
$ tail -f -n 100 /var/log/syslog
# Show last 100 lines, then follow
$ tail -f /var/log/apache2/access.log
# 实时监控Web服务器访问日志
$ tail -f -n 100 /var/log/syslog
# 显示最后100行，然后跟踪

Skip Header Lines跳过标题行

$ tail -n +2 data.csv
# Skip first line (header), show rest
$ tail -n +2 data.csv
# 跳过第一行（标题），显示其余部分

Memory Tricks记忆技巧

🐕 "tail" = the tail/end of something - Think of a dog's tail at the back!

tail Commandtail命令