Linux in a Nutshell, Fifth Edition

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Chapter 3: Linux Commands

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

tac

tac [options] [file]

Named for the common command cat, tac prints files in reverse to

standard output. Without a filename or with -, it reads from stan-

dard input. By default, tac reverses the order of the lines, printing

the last line first.

Options

-b, --before

Print separator (by default a newline) before the string it

delimits.

-r, --regex

Expect separator to be a regular expression.

-s string, --separator=string

Specify alternate separator (default is newline).

--help

Print a help message and then exit.

--version

Print version information and then exit.

tail

tail [options] [files]

Print the last 10 lines of each named file (or standard input if - is

specified) on standard output. If more than one file is specified, the

output includes a header at the beginning of each file:

= =>filename<= =

For options that take the number of bytes or lines as an argument,

you prepend a plus sign (+) to num to begin printing with the

numth item. These options can also specify a block size:

b 512 bytes

k 1 kilobyte

m 1 megabyte

Options

-c num, --bytes num

Print the last num bytes.

-f, --follow[=name|descriptor]

Don’t quit at the end of file; “follow” file as it grows and end

when the user presses Ctrl-C. Following by file descriptor is

the default, so -f, --follow, and --follow=descriptor ...