usr/src/usr.bin/tail/tail.1

.TH TAIL 1L \" -*- nroff -*-
.SH NAME
tail \- output the last part of files
.SH SYNOPSIS
.B tail
[\-c [+]N[bkm]] [\-n [+]N] [\-fqv] [\-\-bytes=[+]N[bkm]] [\-\-lines=[+]N]
[\-\-follow] [\-\-quiet] [\-\-silent] [\-\-verbose] [file...]

.B tail
[{\-,+}Nbcfklmqv] [file...]
.SH DESCRIPTION
This manual page
documents the GNU version of
.BR tail .
.B tail
prints the last part (10 lines by default) of each given file; it
reads from standard input if no files are given or when a filename of
`\-' is encountered.  If more than one file is given, it prints a
header consisting of the file's name enclosed in `==>' and `<=='
before the output for each file.
.PP
The GNU
.B tail
can output any amount of data, unlike the Unix version, which uses a
fixed size buffer.  It has no
.I \-r
option (print in reverse).  Reversing a file is really a different job
from printing the end of a file; the BSD
.B tail
can only reverse files that are at most as large as its buffer, which
is typically 32k.  A reliable and more versatile way to reverse files is
the GNU
.B tac
command.
.SS OPTIONS
.PP
.B tail
accepts two option formats: the new one, in which numbers are
arguments to the option letters, and the old one, in which a `+' or
`\-' and optional number precede any option letters.
.PP
If a number (`N') starts with a `+',
.B tail
begins printing with the Nth item from the start of each file, instead
of from the end.
.TP
.I "\-c N, \-\-bytes N"
Tail by N bytes.  N is a nonzero integer, optionally followed by one
of the following characters to specify a different unit.
.RS
.IP b
512-byte blocks.
.IP k
1-kilobyte blocks.
.IP m
1-megabyte blocks.
.RE
.TP
.I "\-f, \-\-follow"
Loop forever trying to read more characters at the end of the file, on
the assumption that the file is growing.  Ignored if reading from a
pipe.  Cannot be used if more than one file is given.
.TP
.I "\-l, \-n N, \-\-lines N"
Tail by N lines.
.TP
.I "\-q, \-\-quiet, \-\-silent"
Never print filename headers.
.TP
.I "\-v, \-\-verbose"
Always print filename headers.
.PP
The long-named options can be introduced with `+' as well as `\-\-',
for compatibility with previous releases.  Eventually support for `+'
will be removed, because it is incompatible with the POSIX.2 standard.