MDB(1)MDB(1)NAMEmdb - binary file editor
SYNOPSISmdb [ -w ] file [ command ]
DESCRIPTION
Mdb allows inspection of the contents of file. If the -w option is
given, then modification of the contents is also allowed. Mdb accepts
commands of the form
[address] [, count] [command]
If a command is given as an argument, then mdb will execute that com‐
mand, 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 inter‐
preted 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 encoun‐
tered.
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:
[?/]w value
Write the two-byte value to the addressed location.
[?/]W value
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.
SOURCE
/appl/cmd/mdb.b
SEE ALSOdis(6)BUGS
Most of the more useful features of mdb's antecedent db are unimple‐
mented.
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.
MDB(1)
