.\"-
.\" Copyright (c) 2007-2008 Robert N. M. Watson
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" $FreeBSD$
.\"
.Dd December 24, 2008
.Dt DDB 8
.Os
.Sh NAME
.Nm ddb
.Nd "configure DDB kernel debugger properties"
.Sh SYNOPSIS
.Nm
.Cm capture
.Op Fl M core
.Op Fl N system
.Cm print
.Nm
.Cm capture
.Op Fl M core
.Op Fl N system
.Cm status
.Nm
.Cm script
.Ar scriptname
.Nm
.Cm script
.Ar scriptname Ns = Ns Ar script
.Nm
.Cm scripts
.Nm
.Cm unscript
.Ar scriptname
.Nm
.Ar pathname
.Sh DESCRIPTION
The
.Nm
utility configures certain aspects of the
.Xr ddb 4
kernel debugger from user space that are not configured at compile-time or
easily via
.Xr sysctl 8
MIB entries.
.Pp
To ease configuration, commands can be put in a file which is processed using
.Nm
as shown in the last synopsis line.
An absolute
.Ar pathname
must be used.
The file will be read line by line and applied as arguments to the
.Nm
utility.
Whitespace at the beginning of lines will be ignored as will lines where the
first non-whitespace character is
.Ql # .
.Sh OUTPUT CAPTURE
The
.Nm
utility can be used to extract the contents of the
.Xr ddb 4
output capture buffer of the current live kernel, or from the crash dump of a
kernel on disk.
The following debugger commands are available from the command line:
.Bl -tag -width indent
.It Xo
.Cm capture
.Op Fl M Ar core
.Op Fl N Ar system
.Cm print
.Xc
Print the current contents of the
.Xr ddb 4
output capture buffer.
.It Xo
.Cm capture
.Op Fl M Ar core
.Op Fl N Ar system
.Cm status
.Xc
Print the current status of the
.Xr ddb 4
output capture buffer.
.El
.Sh SCRIPTING
The
.Nm
utility can be used to configure aspects of
.Xr ddb 4
scripting from user space; scripting support is described in more detail in
.Xr ddb 4 .
Each of the debugger commands is available from the command line:
.Bl -tag -width indent
.It Cm script Ar scriptname
Print the script named
.Ar scriptname .
.It Cm script Ar scriptname Ns = Ns Ar script
Define a script named
.Ar scriptname .
As many scripts contain characters interpreted in special ways by the shell,
it is advisable to enclose
.Ar script
in quotes.
.It Cm scripts
List currently defined scripts.
.It Cm unscript Ar scriptname
Delete the script named
.Ar scriptname .
.El
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
The following example defines a script that will execute when the kernel
debugger is entered as a result of a break signal:
.Bd -literal -offset indent
ddb script kdb.enter.break="show pcpu; bt"
.Ed
.Pp
The following example will delete the script:
.Pp
.Dl "ddb unscript kdb.enter.break"
.Pp
For further examples, see the
.Xr ddb 4
and
.Xr textdump 4
manual pages.
.Sh SEE ALSO
.Xr ddb 4 ,
.Xr textdump 4 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 7.1 .
.Sh AUTHORS
.An Robert N M Watson
.Sh BUGS
Ideally,
.Nm
would not exist, as all pertinent aspects of
.Xr ddb 4
could be configured directly via
.Xr sysctl 8 .