O comando tail pode ser utilizado para examinar as últimas linhas de um arquivo.
O comando:
$ tail /etc/passwd
Irá exibir as dez íltimas linhas do /etc/passwd.
E possível também especificar as o número de linhas a serem exibidas, ao invés das dez linhas que o comando adota como padrão:
$ tail -n 20 /etc/passwd
Uma diretiva muito útil é "-f", que permite a visualização dinãmica de um arquivo, ou seja, as linhas são exibidas na tela na medida em quesão geradas.
TAIL(1) User Commands TAIL(1)
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.
-c, --bytes=K
output the last K bytes; alternatively, use -c +K to output
bytes starting with the Kth of each file
-f, --follow[={name|descriptor}]
output appended data as the file grows; -f, --follow, and --fol‐
low=descriptor are equivalent
-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 lines 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)
--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 even when it is or becomes inaccessi‐
ble; useful when following by name, i.e., with --follow=name
-s, --sleep-interval=N
with -f, sleep for approximately N 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 K (the number of bytes or lines) is a `+',
print beginning with the Kth item from the start of each file, other‐
wise, print the last K items in the file. K may have a multiplier suf‐
fix: 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 descrip‐
tor (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.
AUTHOR
Written by Paul Rubin, David MacKenzie, Ian Lance Taylor, and Jim Mey‐
ering.
REPORTING BUGS
Report tail bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report tail translation bugs to <http://translationproject.org/team/>
COPYRIGHT
Copyright © 2010 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
The full documentation for tail is maintained as a Texinfo manual. If
the info and tail programs are properly installed at your site, the
command
info coreutils 'tail invocation'
should give you access to the complete manual.
GNU coreutils 8.5 April 2010 TAIL(1)
