为了从冗长的日志中查看最后的执行结果，可以利用tail显示指定文件的最后几n行。

1.tail基本用法

tail -n 5 example.txt
>>>输出
last 5
last 4
last 3
last 2
last 1

下面是tail 的帮助文档：

Usage: tail [OPTION]... [FILE]...
Print the last 10 lines of each FILE to standard output.
# 不加参数默认输出最后十行
With more than one FILE, precede each with a header giving the file name.
# 也可针对多个文件输出

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -c, --bytes=[+]NUM       output the last NUM bytes; or use -c +NUM to output starting with byte NUM of each file
  # 按比特输出
  -f, --follow[={name|descriptor}]
                            output appended data as the file grows; an absent option argument means 'descriptor'
  -F                       same as --follow=name --retry
  # 随文件增加显示
  -n, --lines=[+]NUM       output the last NUM lines, instead of the last 10;
                             or use -n +NUM to output starting with line NUM
  # 最常使用的参数，输出最后n行。+n则表示输出开始n行
      --max-unchanged-stats=N
                           with --follow=name, reopen a FILE which has not
                             changed size after N (default 5) iterations
                             to see if it has been unlinked or renamed
                             (this is the usual case of rotated log files);
                             with inotify, this option is rarely useful
      --pid=PID            with -f, terminate after process ID, PID dies
  -q, --quiet, --silent    never output headers giving file names
      --retry              keep trying to open a file if it is inaccessible
  -s, --sleep-interval=N   with -f, sleep for approximately N seconds
                             (default 1.0) between iterations;
                             with inotify and --pid=P, check process P at
                             least once every N seconds
  -v, --verbose            always output headers giving file names
  -z, --zero-terminated    line delimiter is NUL, not newline
      --help     display this help and exit
      --version  output version information and exit

NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

With --follow (-f), tail defaults to following the file descriptor, which
means that even if a tail'ed file is renamed, tail will continue to track
its end.  This default behavior is not desirable when you really want to
track the actual name of the file, not the file descriptor (e.g., log
rotation).  Use --follow=name in that case.  That causes tail to track the
named file in a way that accommodates renaming, removal and creation.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Report tail translation bugs to <http://translationproject.org/team/>
Full documentation at: <http://www.gnu.org/software/coreutils/tail>
or available locally via: info '(coreutils) tail invocation'

ref：

https://blog.csdn.net/luo200618/article/details/52510638

https://blog.csdn.net/piaoxuan1987/article/details/78765124

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