kvar.8

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH kvar 8 RISC
.SH Name
kvar \- modify RISC kernel variables in memory or on disk
.SH Syntax
.B /usr/etc/kvar -r(b|w|l) [\|\fIoptions\fP\|] vmunix
.br
.B /usr/etc/kvar -w(b|w|l) [\|\fIoptions\fP\|] vmunix
.SH Description
.NXR "kernel variables" "modifying"
.NXR "kvar command"
The 
.PN kvar 
command allows you to read or write RISC kernel variables, either 
in the on-disk image of 
.PN vmunix
or the active in-memory image. 
The \fB\-r\fP form of the command does variable reads; the \fB\-w\fP form 
does variable writes. 
The variable length qualifiers are: b (1 byte), w (word, or 2 bytes), 
and l (longword, or 4 bytes).
.PP
Variable contents are displayed in hexadecimal format.
.SH Options
.TP 12
\fB\-a\fI address\fR
Specifies the \fIaddress\fP of the kernel variable. 
Either the \fB\-a\fP 
or \fB\-s\fP option must be specified.  
The \fIaddress\fP is specified as either a positive decimal or 
hexadecimal constant.
.TP
\fB\-k\fP
Instructs 
.PN kvar
to use the in-memory image of 
.PN vmunix 
.Pn ( /dev/kmem ).
The default is to use the on-disk copy.
.TP
\fB\-l\fR
Searches for a local symbol. The default is a global symbol search.
.TP
\fB\-o\fI offset\fR
Adds an \fIoffset\fP to the address (or address of the symbol name).
The 
.I offset 
value is specified as either a positive decimal or hexadecimal constant.
.TP
\fB\-s\fI name\fR
Specifies the \fIname\fP of the kernel variable.
.TP
\fB\-v\fI value\fR
Specifies the new \fIvalue\fP to be assigned by the \fB\-w\fP form of 
.PN kvar .
The \fB\-v\fP option is ignored if the 
\fB\-r\fP form of
.PN kvar 
is being used. 
The \fIvalue\fP is specified as either a positive decimal or 
hexadecimal constant.
.SH Restrictions
You must have appropriate file access permissions for 
.PN /vmunix
(and for
.PN /dev/kmem 
with the \fB\-k\fP option).
.PP
The 
.PN kvar
command is available only on RISC systems.
For VAX systems, use 
.MS adb 1 
to modify kernel variables.
.SH Examples
This example reads the variable `udpcksum' from the running kernel image:
.IP "" 5
%
.B kvar \-k \-rl \-s udpcksum /vmunix
.PP
This example sets the `xyz' variable to zero in the running kernel image:
.IP
%
.B "kvar \-k \-wl \-s xyz \-v 0 /vmunix"
.PP
This example sets the variable `xyz' to -1 in the on-disk image of 
.PN vmunix 
making this value persistent across reboots:
.IP
%
.B "kvar \-wl \-s xyz \-v 0xffffffff /vmunix"
.PP
This example sets to zero 1 byte at offset 2 from address 0x80161a98 in the 
running kernel image:
.IP
%
.B "kvar \-k \-wb \-o 2 \-a 0x80161a98 /vmunix"
.SH Files
.PN /dev/kmem
.br
.PN /vmunix
.SH See Also
adb(1), dbx(1)