The tail command is the complement of the head command, and filters a stream so that only the
end of the stream is passed to stdout. This is often used to get a quick summary of the contents
of a file, or to target specific lines by index in a pipeline.
The call signature is:
tail {options} {path}
If path is specified, that file will be read and streamed to stdin. If path is omitted or
set to -, then this command will operate on the stream that is piped or redirected to
stdin.
The most common option is -n (or the --lines long option), which defines the index of
the line from which content is passed to stdout. By default the index is 10.
To demonstrate, let's work with our numbers.txt file, which contains a simple list of numbers from one through twelve.:
Although this file contains 12 lines of text, only the last 10 lines are passed to stdout,
Now lets change the index to 3:
The tail command also allows the index to be negative, so that lines can be filtered relative to
the beginning of the file. For example, to filter out only the first 5 lines the index can be
set to -5: