1.\" Copyright (c) 2001 2.\" Jeffrey D. Wheelhouse. All rights reserved. 3.\" 4.\" This code was originally developed by Jeff Wheelhouse (jdw@wwwi.com). 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY JEFF WHEELHOUSE ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN 18.\" NO EVENT SHALL JEFF WHEELHOUSE BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING BUT NOT 20.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 21.\" OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 22.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 23.\" NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 24.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $Id: clog.8,v 1.2 2001/10/02 04:41:21 jdw Exp $ 27.\" 28.Dd May 6, 2006 29.Dt CLOG 8 30.Os 31.Sh NAME 32.Nm clog 33.Nd display or initialize a circular system log 34.Sh SYNOPSIS 35.Nm 36.Op Fl f 37.Op Fl i Fl s Ar size 38.Ar logfile 39.Sh DESCRIPTION 40.Nm 41displays or initializes a circular log file. 42.Pp 43The options are as follows: 44.Bl -tag -width indent 45.It Fl f 46Display the contents of the circular logfile 47.Ar logfile , 48then go into a loop waiting for new material to arrive. 49This is essentially the same as using the 50.Fl f 51option of the 52.Xr tail 1 53command on a standard syslog file. 54.It Fl i 55Initialize 56.Ar logfile 57rather than reading it. 58This option requires the 59.Fl s 60option. 61If 62.Ar logfile 63already exists, it will be truncated and recreated by this command. 64.It Fl s 65This option specifies the size in bytes of the circular logfile that should 66be created. 67This option requires the 68.Fl i 69option. 70.El 71.Sh ABOUT CIRCULAR LOGFILES 72The 73.Nm 74command supports circular logfiles for 75.Xr syslogd 8 . 76A circular logfile differs from a standard syslog file in that it has a fixed 77size. 78It does not grow, and does not need to be rotated. 79When 80.Xr syslogd 8 81reaches the end of a circular logfile, it simply begins again at the beginning, 82overwriting the oldest data. 83The circular logfile also contains information allowing 84.Nm 85to establish what parts of the file are valid, and in what order they should 86be displayed. 87.Pp 88Circular logfiles are primarily useful for their ability to control the amount 89of storage devoted to logfiles. 90This may be valuable when storage space is at a premium or when the 91consequences of running out of storage space are unacceptable. 92Circular logfiles can safely be used on a memory disk (see 93.Xr md 4 ) . 94.Pp 95Circular logfiles are also useful to catch messages that are generated rapidly 96but soon lose relevance, such as messages logged at debug priority. 97.Sh SEE ALSO 98.Xr syslog.conf 5 , 99.Xr syslogd 8 100.Sh HISTORY 101The 102.Nm 103command was written for 104.Fx 4.3 105and was imported into 106.Dx 1.1 . 107