tail - Unix, Linux Command

NAME

tail - output the last part of files

SYNOPSIS

tail [OPTION]... [FILE]...

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.

Tag	Description
--retry	keep trying to open a file even if it is inaccessible when tail starts or if it becomes inaccessible later; useful when following by name, i.e., with --follow=name
-c, --bytes=N
	output the last N bytes
-f, --follow[={name\|descriptor}]
	output appended data as the file grows; -f, --follow, and --follow=descriptor are equivalent
-F	same as --follow=name --retry
-n, --lines=N
	output the last N lines, instead of the last 10
--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)
--pid=PID
	with -f, terminate after process ID, PID dies
-q, --quiet, --silent
	never output headers giving file names
-s, --sleep-interval=S
	with -f, sleep for approximately S seconds (default 1.0) between iterations.
-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 N (the number of bytes or lines) is a ‘+’, print beginning with the Nth item from the start of each file, otherwise, print the last N items in the file. N may have a multiplier suffix: b 512, k 1024, m 1024*1024.

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 by reopening it periodically to see if it has been removed and recreated by some other program.

‘_POSIX2_VERSION’ COMPATIBILITY ISSUES:

On older systems, the leading ‘-’ can be replaced by ‘+’ in the obsolete option syntax with the same meaning as in counts, and obsolete usage overrides normal usage when the two conflict. This obsolete behavior can be enabled or disabled with the ‘_POSIX2_VERSION’ environment variable, but portable scripts should avoid commands whose behavior depends on this variable.
For example, use ‘tail -- - main.c’ or ‘tail main.c’ rather than the ambiguous ‘tail - main.c’, ‘tail -c4’ or ‘tail -c 10 4’ rather than the ambiguous ‘tail -c 4’, and ‘tail ./+4’ or ‘tail -n +4’ rather than the ambiguous ‘tail +4’. You can work around those compatibility problems by setting ‘_POSIX2_VERSION=199209’ in your environment.

AUTHOR

Written by Paul Rubin, David MacKenzie, Ian Lance Taylor, and Jim Meyering.

REPORTING BUGS

Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

Copyright © 2006 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the extent permitted by law.