-'\" -*- coding: UTF-8 -*-
.\" Copyright (C) 2010 Michael Krapp
.\"
.\" This program is free software; you can redistribute it and/or modify
-.\" it under the terms of the GNU General Public License as published by
+.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\"
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
-.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with this program; if not, write to the Free Software
.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
.\"
-.TH UTMPDUMP 1 "Februar 8, 2010" "" "Linux System Administrator's Manual"
+.TH UTMPDUMP 1 "July 2014" "util-linux" "User Commands"
.SH NAME
utmpdump \- dump UTMP and WTMP files in raw format
.SH SYNOPSIS
+.BR utmpdump " [options]"
+.RI [ filename ]
+.SH DESCRIPTION
+.B utmpdump
+is a simple program to dump UTMP and WTMP files in raw format, so they
+can be examined.
.B utmpdump
-.RB [ \-frh ]
+reads from stdin unless a
.I filename
-.SH DESCRIPTION
-\fButmpdump\fP is a simple program to dump UTMP and WTMP files
-in raw format, so they can be examined.
+is passed.
.SH OPTIONS
-.IP "\fB\-f, \-\-follow\fP"
-output appended data as the file grows.
-.IP "\fB\-r, \-\-reverse\fP
-Undump, write back edited login information into utmp or wtmp files.
-.IP "\fB\-h, \-\-help\fP"
-Print a help text and exit.
-.IP "\fB\-V, \-\-version\fP"
-Output version information and exit.
+.TP
+.BR \-f , " \-\-follow"
+Output appended data as the file grows.
+.TP
+.BR \-o , " \-\-output " \fIfile
+Write command output to \fIfile\fR instead of standard output.
+.TP
+.BR \-r , " \-\-reverse"
+Undump, write back edited login information into the utmp or wtmp files.
+.TP
+.BR \-V , " \-\-version"
+Display version information and exit.
+.TP
+.BR \-h , " \-\-help"
+Display help text and exit.
.SH NOTES
-utmpdump can be useful in cases of corrupted utmp or wtmp entries. It can dump
-out utmp/wtmp to an ASCII file, then that file can be edited to remove bogus
-entries and reintegrated, using
-.PP
-.sp 1
-.in +1c
-.nf
-\fButmpdump -r < ascii file > wtmp\fP
-.fi
-.in -1c
-.sp 1
-but be warned as
.B utmpdump
-was written for debugging purpose only.
+can be useful in cases of corrupted utmp or wtmp entries. It can dump
+out utmp/wtmp to an ASCII file, which can then be edited to remove
+bogus entries, and reintegrated using:
+.PP
+.RS
+.B utmpdump \-r < ascii_file > wtmp
+.RE
+.PP
+But be warned,
+.B utmpdump
+was written for debugging purposes only.
+.SS File formats
+.PP
+Only the binary version of the
+.BR utmp (5)
+is standardised. Textual dumps may become incompatible in future.
+.PP
+The version 2.28 was the last one that printed text output using
+.BR ctime (3)
+timestamp format. Newer dumps use millisecond precision ISO-8601 timestamp
+format in UTC-0 timezone. Conversion from former timestamp format can be
+made to binary, although attempt to do so can lead the timestamps to drift
+amount of timezone offset.
.SH BUGS
You may
.B not
-use the option \fB\-r\fP as the format for the
-utmp/wtmp files strongly depends on the
-input format. This tool was
+use the
+.B \-r
+option, as the format for the utmp/wtmp files strongly depends on the input
+format. This tool was
.B not
-written for normal use but for debugging.
+written for normal use, but for debugging only.
.SH AUTHOR
Michael Krapp
.SH "SEE ALSO"
.BR last (1),
.BR w (1),
.BR who (1),
-.BR utmp (5),
+.BR utmp (5)
+.SH AVAILABILITY
+The utmpdump command is part of the util-linux package and is available
+from
+.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+Linux Kernel Archive
+.UE .
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