Linux shell-tail

Posted 2020-09-06 StephenLu

使用tail --help查看命令用于备忘

tail [  -f ] [  -c Number |  -n Number |  -m Number |  -b Number |  -k Number ] [ File ]

Usage: tail [OPTION]... [FILE]...
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=K output the last K bytes; or use -c +K to output
bytes starting with the Kth of each file
-f, --follow[={name|descriptor}]
output appended data as the file grows;
an absent option argument means ‘descriptor‘

(PS:参数-f使tail不停地去读最新的内容;e.g:tail -f -n 500监控显示500尾行内容)
-F same as --follow=name --retry
-n, --lines=K output the last K lines, instead of the last 10;
or use -n +K to output starting with the Kth
--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
--help display this help and exit
--version output version information and exit

If the first character of K (the number of bytes or lines) is a ‘+‘,
print beginning with the Kth item from the start of each file, otherwise,
print the last K items in the file. K 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.