Linux命令之tail详解

tail

概述

tail 命令可用于查看文件的内容,有一个常用的参数 -f 常用于查阅正在改变的日志文件。

tail -f filename 会把 filename 文件里的最尾部的内容显示在屏幕上,并且不断刷新,只要 filename 更新就可以看到最新的文件内容。

语法

tail [参数] [文件]  

[参数]

  • -f 循环读取
  • -q 不显示处理信息
  • -v 显示详细的处理信息
  • -c<数目> 显示的字节数
  • -n<行数> 显示文件的尾部 n 行内容
  • --pid=PID 与-f合用,表示在进程ID,PID死掉之后结束
  • -q, --quiet, --silent 从不输出给出文件名的首部
  • -s, --sleep-interval=S 与-f合用,表示在每次反复的间隔休眠S秒

examples

显示rabbit@node01.log 文件的最后 10 行

[root@node01 ~]# tail  /var/log/rabbitmq/rabbit\@node01.log 
2021-04-04 20:57:24.869 [info] <0.18967.3> Closing all channels from connection '[::1]:55712 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.869 [info] <0.18975.3> accepting AMQP connection <0.18975.3> ([::1]:55716 -> [::1]:5672)
2021-04-04 20:57:24.869 [error] <0.18975.3> closing AMQP connection <0.18975.3> ([::1]:55716 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:57:24.871 [info] <0.18972.3> Closing all channels from connection '[::1]:55714 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.872 [info] <0.18980.3> accepting AMQP connection <0.18980.3> ([::1]:55718 -> [::1]:5672)
2021-04-04 20:57:24.873 [error] <0.18980.3> closing AMQP connection <0.18980.3> ([::1]:55718 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:57:24.873 [info] <0.18977.3> Closing all channels from connection '[::1]:55716 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.877 [info] <0.18982.3> Closing all channels from connection '[::1]:55718 -> [::1]:5672' because it has been closed
[root@node01 ~]# 

要跟踪名为 rabbit@node01.log 的文件的增长情况(实时读取、循环读取)

[root@node01 ~]# tail -f /var/log/rabbitmq/rabbit\@node01.log 
2021-04-04 20:57:24.869 [info] <0.18967.3> Closing all channels from connection '[::1]:55712 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.869 [info] <0.18975.3> accepting AMQP connection <0.18975.3> ([::1]:55716 -> [::1]:5672)
2021-04-04 20:57:24.869 [error] <0.18975.3> closing AMQP connection <0.18975.3> ([::1]:55716 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:57:24.871 [info] <0.18972.3> Closing all channels from connection '[::1]:55714 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.872 [info] <0.18980.3> accepting AMQP connection <0.18980.3> ([::1]:55718 -> [::1]:5672)
2021-04-04 20:57:24.873 [error] <0.18980.3> closing AMQP connection <0.18980.3> ([::1]:55718 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:57:24.873 [info] <0.18977.3> Closing all channels from connection '[::1]:55716 -> [::1]:5672' because it has been closed
2021-04-04 20:57:24.877 [info] <0.18982.3> Closing all channels from connection '[::1]:55718 -> [::1]:5672' because it has been closed
[root@node01 ~]# tail -f  /var/log/rabbitmq/rabbit\@node01.log 
2021-04-04 20:58:39.867 [info] <0.19143.3> Closing all channels from connection '[::1]:55752 -> [::1]:5672' because it has been closed
2021-04-04 20:58:39.867 [info] <0.19151.3> accepting AMQP connection <0.19151.3> ([::1]:55756 -> [::1]:5672)
2021-04-04 20:58:39.868 [error] <0.19151.3> closing AMQP connection <0.19151.3> ([::1]:55756 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:58:39.869 [info] <0.19148.3> Closing all channels from connection '[::1]:55754 -> [::1]:5672' because it has been closed
2021-04-04 20:58:39.870 [info] <0.19156.3> accepting AMQP connection <0.19156.3> ([::1]:55758 -> [::1]:5672)
2021-04-04 20:58:39.870 [error] <0.19156.3> closing AMQP connection <0.19156.3> ([::1]:55758 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 20:58:39.870 [info] <0.19153.3> Closing all channels from connection '[::1]:55756 -> [::1]:5672' because it has been closed
2021-04-04 20:58:39.874 [info] <0.19158.3> Closing all channels from connection '[::1]:55758 -> [::1]:5672' because it has been closed
一直更新

显示文件rabbit@node01.log 的内容,从第100999行至文件末尾

[root@node01 ~]# tail -n +100999 /var/log/rabbitmq/rabbit\@node01.log 
2021-04-04 21:01:24.883 [info] <0.19543.3> accepting AMQP connection <0.19543.3> ([::1]:55846 -> [::1]:5672)
2021-04-04 21:01:24.883 [error] <0.19543.3> closing AMQP connection <0.19543.3> ([::1]:55846 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:24.884 [info] <0.19540.3> Closing all channels from connection '[::1]:55844 -> [::1]:5672' because it has been closed
2021-04-04 21:01:24.887 [info] <0.19545.3> Closing all channels from connection '[::1]:55846 -> [::1]:5672' because it has been closed
2021-04-04 21:01:39.864 [info] <0.19563.3> accepting AMQP connection <0.19563.3> ([::1]:55848 -> [::1]:5672)
2021-04-04 21:01:39.864 [error] <0.19563.3> closing AMQP connection <0.19563.3> ([::1]:55848 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:39.870 [info] <0.19565.3> Closing all channels from connection '[::1]:55848 -> [::1]:5672' because it has been closed
2021-04-04 21:01:39.871 [info] <0.19568.3> accepting AMQP connection <0.19568.3> ([::1]:55850 -> [::1]:5672)
2021-04-04 21:01:39.871 [error] <0.19568.3> closing AMQP connection <0.19568.3> ([::1]:55850 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:39.876 [info] <0.19573.3> accepting AMQP connection <0.19573.3> ([::1]:55852 -> [::1]:5672)
2021-04-04 21:01:39.877 [error] <0.19573.3> closing AMQP connection <0.19573.3> ([::1]:55852 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:39.879 [info] <0.19570.3> Closing all channels from connection '[::1]:55850 -> [::1]:5672' because it has been closed
2021-04-04 21:01:39.880 [info] <0.19578.3> accepting AMQP connection <0.19578.3> ([::1]:55854 -> [::1]:5672)
2021-04-04 21:01:39.880 [error] <0.19578.3> closing AMQP connection <0.19578.3> ([::1]:55854 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:39.881 [info] <0.19575.3> Closing all channels from connection '[::1]:55852 -> [::1]:5672' because it has been closed
2021-04-04 21:01:39.885 [info] <0.19580.3> Closing all channels from connection '[::1]:55854 -> [::1]:5672' because it has been closed
2021-04-04 21:01:54.864 [info] <0.19598.3> accepting AMQP connection <0.19598.3> ([::1]:55856 -> [::1]:5672)
2021-04-04 21:01:54.864 [error] <0.19598.3> closing AMQP connection <0.19598.3> ([::1]:55856 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:54.869 [info] <0.19603.3> accepting AMQP connection <0.19603.3> ([::1]:55858 -> [::1]:5672)
2021-04-04 21:01:54.869 [error] <0.19603.3> closing AMQP connection <0.19603.3> ([::1]:55858 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:54.870 [info] <0.19600.3> Closing all channels from connection '[::1]:55856 -> [::1]:5672' because it has been closed
2021-04-04 21:01:54.875 [info] <0.19608.3> accepting AMQP connection <0.19608.3> ([::1]:55860 -> [::1]:5672)
2021-04-04 21:01:54.876 [error] <0.19608.3> closing AMQP connection <0.19608.3> ([::1]:55860 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:54.879 [info] <0.19605.3> Closing all channels from connection '[::1]:55858 -> [::1]:5672' because it has been closed
2021-04-04 21:01:54.880 [info] <0.19613.3> accepting AMQP connection <0.19613.3> ([::1]:55862 -> [::1]:5672)
2021-04-04 21:01:54.881 [error] <0.19613.3> closing AMQP connection <0.19613.3> ([::1]:55862 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:01:54.883 [info] <0.19610.3> Closing all channels from connection '[::1]:55860 -> [::1]:5672' because it has been closed
2021-04-04 21:01:54.889 [info] <0.19615.3> Closing all channels from connection '[::1]:55862 -> [::1]:5672' because it has been closed
[root@node01 ~]# 

显示文件 rabbit@node01.log 的最后 500 个字符

[root@node01 ~]# tail -c 500 /var/log/rabbitmq/rabbit\@node01.log 
> closing AMQP connection <0.19790.3> ([::1]:55902 -> [::1]:5672):
{bad_header,<<"GET /api">>}
2021-04-04 21:03:09.877 [info] <0.19782.3> Closing all channels from connection '[::1]:55898 -> [::1]:5672' because it has been closed
2021-04-04 21:03:09.877 [info] <0.19787.3> Closing all channels from connection '[::1]:55900 -> [::1]:5672' because it has been closed
2021-04-04 21:03:09.879 [info] <0.19792.3> Closing all channels from connection '[::1]:55902 -> [::1]:5672' because it has been closed
[root@node01 ~]# 
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