tail命令用于从文件的尾部读取指定数量的数据行，并将其显示在屏幕上，默认查看10行数据。
命令格式：
tail [OPTION]… [FILE]…
选项：
-n, –lines=K：显示文件末尾的K行；
-f, –follow：跟踪文件的末尾，实时显示新增的内容；
-q, –quiet：不显示头部信息；
-v, –verbose：显示头部信息；
-c, –bytes=K：显示文件末尾的K字节；
-z, –zero-terminated：以NUL字符作为行结束符；
DESCRIPTION
Print the last 10 lines of each FILE to standard output. With more than one FILE, precede each with a header
giving the file name.
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
-f, --follow[={name|descriptor}]
output appended data as the file grows;
an absent option argument means 'descriptor'
-F same as --follow=name --retry
-n, --lines=[+]NUM
output the last NUM lines, instead of the last 10; or use -n +NUM to output starting with line NUM
--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. 例子：
例1，查看文件末尾内容
study@DESKTOP:/var/log$ tail dpkg.log
2022-03-24 22:18:46 status installed x11-utils:amd64 7.7+5
2022-03-24 22:18:46 trigproc systemd:amd64 245.4-4ubuntu3.15 <none>
2022-03-24 22:18:46 status half-configured systemd:amd64 245.4-4ubuntu3.15
2022-03-24 22:18:46 status installed systemd:amd64 245.4-4ubuntu3.15
2022-03-24 22:18:46 trigproc man-db:amd64 2.9.1-1 <none>
2022-03-24 22:18:46 status half-configured man-db:amd64 2.9.1-1
2022-03-24 22:18:46 status installed man-db:amd64 2.9.1-1
2022-03-24 22:18:46 trigproc libc-bin:amd64 2.31-0ubuntu9.7 <none>
2022-03-24 22:18:46 status half-configured libc-bin:amd64 2.31-0ubuntu9.7
2022-03-24 22:18:46 status installed libc-bin:amd64 2.31-0ubuntu9.7
例2，查看文件末尾，按照指定行数查看
study@DESKTOP:/var/log$ tail -5 dpkg.log
2022-03-24 22:18:46 status half-configured man-db:amd64 2.9.1-1
2022-03-24 22:18:46 status installed man-db:amd64 2.9.1-1
2022-03-24 22:18:46 trigproc libc-bin:amd64 2.31-0ubuntu9.7 <none>
2022-03-24 22:18:46 status half-configured libc-bin:amd64 2.31-0ubuntu9.7
2022-03-24 22:18:46 status installed libc-bin:amd64 2.31-0ubuntu9.7