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|
.TH MDB 1
.SH NAME
mdb - binary file editor
.SH SYNOPSIS
.B mdb
[
.B -w
]
.I file
[
.I command
]
.SH DESCRIPTION
.I Mdb
allows inspection of the contents
of
.IR file .
If the
.B -w
option is given, then modification of the contents is also
allowed.
.I Mdb
accepts commands of the form
.IP
.RI [ address ]
.RB [ ,
.IR count ]
.RI [ command ]
.PP
If a
.I command
is given as an argument, then
.I mdb
will execute that command, otherwise
it will read and execute commands from the standard input.
If
.I address
is present then the current position, called `dot', is
set to
.IR address.
Initially dot is set to 0.
.I Command
is repeated
.I count
times with dot advancing between repetitions. The default
count is 1.
.I Address
and
.I count
are expressions.
.SS Expressions
Expressions take one of the following forms:
.TP 10
\&.
The value of dot.
.TP
+
The value of dot.
.TP
^
The value of dot.
.TP
"
The value of the last address typed.
.TP
.I integer
A number, decimal by default. A
.RB ` 0 '
prefix causes
it to be interpreted as octal; a
.RB ` 0x '
prefix causes it to be interpreted as hexadecimal.
.TP
.BI ( expr )
The value of the expression
.IR expr .
.PP
.I Operators
.RS
.TP
.IB e1 + e2
Integer addition.
.TP
.IB e1 - e2
Integer subtraction.
.TP
.IB e1 * e2
Integer multiplication.
.TP
.IB e1 % e2
Integer division. (N.B.
.I not
modulus).
.TP
.IB e1 | e2
Bitwise disjunction.
.TP
.IB e1 & e2
Bitwise conjunction.
.RE
.SS Commands
Commands have the following syntax:
.TP
.BI / f
Locations starting at
.I address
in
.I file
are printed according to the format
.IR f .
.TP
.BI ? f
Same as
.RB ` / '.
.TP
.BI = f
The value of
.I address
itself is printed according to the format
.IR f .
.PP
A
.I format
consists of one or more characters that specify
a style of printing. Each
.I format
fetches some data, prints it, and if the
.I command
is not
.RB ` = ',
advances dot by the amount of data fetched.
All data is assumed to be held in little-endian
form (least significant byte first).
.RS
.TP
.PD 0
.B o
Print a two-byte integer in octal.
.TP
.B O
Print a four-byte integer in octal.
.TP
.B d
Print a two-byte integer in decimal.
.TP
.B D
Print a four-byte integer in decimal.
.TP
.B u
Print a two-byte integer in unsigned decimal.
.TP
.B U
Print a four-byte integer in unsigned decimal.
.TP
.B b
Print a single byte in hexadecimal.
.TP
.B x
Print a two-byte integer in hexadecimal.
.TP
.B X
Print a four-byte integer in hexadecimal.
.TP
.B n
Prints a newline. No data is fetched.
.TP
.B +
Increments dot by 1. No data is printed.
.TP
.B -
Decrements dot by 1. No data is printed.
.TP
.B ^
Increments dot by the size of the last format encountered.
.TP
.B c
Prints a single byte as a character.
.TP
.B C
Prints a single byte as a printable character, converting
it to backslash escaped hex if necessary.
.RE
.PD
There are two other commands:
.TP 10
.RB [ ?/ ] w\ \fIvalue\fP
Write the two-byte
.I value
to the addressed location.
.TP
.RB [ ?/ ] W\ \fIvalue\fP
Write the four-byte
.I value
to the addressed location.
.SH SOURCE
.B /appl/cmd/mdb.b
.SH BUGS
Most of the more useful features of
.IR mdb 's
antecedent
.I db
are unimplemented.
.PP
It is not possible to print strings or UTF-8 characters.
.PP
As there is no ``native'' word format in Inferno,
the assumption that all words are little-endian is hard
to justify.
|
