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[address] [, count] [command]

If a command is given as an argument, then mdb will execute that command, otherwise it will read and execute commands from the standard input. If address is present then the current position, called `dot', is set to address. Initially dot is set to 0. Command is repeated count times with dot advancing between repetitions. The default count is 1. Address and count are expressions.

Expressions

Expressions take one of the following forms:

.

The value of dot.

+

The value of dot.

^

The value of dot.

"

The value of the last address typed.

integer

A number, decimal by default. A `0' prefix causes it to be interpreted as octal; a `0x' prefix causes it to be interpreted as hexadecimal.

(expr)

The value of the expression expr.

Operators

e1+e2

Integer addition.

e1-e2

Integer subtraction.

e1*e2

Integer multiplication.

e1%e2

Integer division. (N.B. not modulus).

e1|e2

Bitwise disjunction.

e1&e2

Bitwise conjunction.

Commands

Commands have the following syntax:

/f

Locations starting at address in file are printed according to the format f.

?f

Same as `/'.

=f

The value of address itself is printed according to the format f.

A format consists of one or more characters that specify a style of printing. Each format fetches some data, prints it, and if the command is not `=', advances dot by the amount of data fetched. All data is assumed to be held in little-endian form (least significant byte first).

o Print a two-byte integer in octal.

O

Print a four-byte integer in octal.

d

Print a two-byte integer in decimal.

D

Print a four-byte integer in decimal.

u

Print a two-byte integer in unsigned decimal.

U

Print a four-byte integer in unsigned decimal.

b

Print a single byte in hexadecimal.

x

Print a two-byte integer in hexadecimal.

X

Print a four-byte integer in hexadecimal.

n

Prints a newline. No data is fetched.

+

Increments dot by 1. No data is printed.

-

Decrements dot by 1. No data is printed.

^

Increments dot by the size of the last format encountered.

c

Prints a single byte as a character.

C

Prints a single byte as a printable character, converting it to backslash escaped hex if necessary.

Other commands include:

[?/]wvalue

Write the two-byte value to the addressed location.

[?/]Wvalue

Write the four-byte value to the addressed location.

[?/]i

Disassemble count instructions starting at address (dot by default).

$modifier

File must be a dis(6) file. Modifier is one of the following subcommands:

D Print the descriptor section.

h

Print the file header.

l

Print the links section.

i

Print the import section.

d

Print the data section.

H

Print exception handler tables.

s

Print the name of the source file.

It is not possible to print strings or UTF-8 characters.

As there is no ``native'' word format in Inferno, the assumption that all words are little-endian is hard to justify.