head用法
command
查看文件的开头N行，支持多文件，多文件时会有标题输出
- head -n N file
head的多种实现
- $ head -N file #N是用户指定的行数
- $ awk 'FNR <= N' file
- $ sed Nq file
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tail用法
command
查看文件的结尾N行，支持多文件，多文件时会有标题输出
- tail -n N file
跟踪日志输出
- $ tail -f logfile #此法持续监控某个文件的输出
- $ less 后加F #等价形式
- # man less : F
- Scroll forward, and keep trying to read when the end of file is reached. Normally this command would be used when already at the end of the file. It is a way to monitor the tail of a file which is growing while it is being viewed. (The behavior is similar to the "tail -f" command.)