adb - debugger
adb [-w] [ objfil [ corfil ] ]
Adb is a general purpose debugging program. It may be used to examine
files and to provide a controlled environment for the execution of UNIX
Objfil is normally an executable program file, preferably containing a
symbol table; if not then the symbolic features of adb cannot be used
although the file can still be examined. The default for objfil is
a.out. Corfil is assumed to be a core image file produced after exe-
cuting objfil; the default for corfil is core.
Requests to adb are read from the standard input and responses are to
the standard output. If the -w flag is present then both objfil and
corfil are created if necessary and opened for reading and writing so
that files can be modified using adb. Adb ignores QUIT; INTERRUPT
causes return to the next adb command.
In general requests to adb are of the form
[address] [, count] [command] [;]
If address is present then dot is set to address. Initially dot is set
to 0. For most commands count specifies how many times the command
will be executed. The default count is 1. Address and count are
The interpretation of an address depends on the context it is used in.
If a subprocess is being debugged then addresses are interpreted in the
usual way in the address space of the subprocess. For further details
of address mapping see ADDRESSES.
. The value of dot.
+ The value of dot incremented by the current increment.
^ The value of dot decremented by the current increment.
" The last address typed.
An octal number if integer begins with a 0; a hexadecimal number
if preceded by #; otherwise a decimal number.
A 32 bit floating point number.
'cccc' The ASCII value of up to 4 characters. \ may be used to escape
< name The value of name, which is either a variable name or a register
name. Adb maintains a number of variables (see VARIABLES) named
by single letters or digits. If name is a register name then
the value of the register is obtained from the system header in
corfil. The register names are r0 ... r5 sp pc ps.
symbol A symbol is a sequence of upper or lower case letters, under-
scores or digits, not starting with a digit. \f[R] may be used
to escape other characters. The value of the symbol is taken
from the symbol table in objfil. An initial _ or ~ will be
prepended to symbol if needed.
In C, the `true name' of an external symbol begins with _. It
may be necessary to utter this name to disinguish it from inter-
nal or hidden variables of a program.
The address of the variable name in the specified C routine.
Both routine and name are symbols. If name is omitted the value
is the address of the most recently activated C stack frame cor-
responding to routine.
(exp) The value of the expression exp.
*exp The contents of the location addressed by exp in corfil.
@exp The contents of the location addressed by exp in objfil.
-exp Integer negation.
~exp Bitwise complement.
Dyadic operators are left associative and are less binding than monadic
e1+e2 Integer addition.
e1-e2 Integer subtraction.
e1*e2 Integer multiplication.
e1%e2 Integer division.
e1&e2 Bitwise conjunction.
e1|e2 Bitwise disjunction.
e1#e2 E1 rounded up to the next multiple of e2.
Most commands consist of a verb followed by a modifier or list of modi-
fiers. The following verbs are available. (The commands `?' and `/'
may be followed by `*'; see ADDRESSES for further details.)
?f Locations starting at address in objfil are printed according to
the format f.
/f Locations starting at address in corfil are printed according to
the format f.
=f The value of address itself is printed in the styles indicated by
the format f. (For i format `?' is printed for the parts of the
instruction that reference subsequent words.)
A format consists of one or more characters that specify a style of
printing. Each format character may be preceded by a decimal integer
that is a repeat count for the format character. While stepping
through a format dot is incremented temporarily by the amount given for
each format letter. If no format is given then the last format is
used. The format letters available are as follows.
o 2 Print 2 bytes in octal. All octal numbers output by adb
are preceded by 0.
O 4 Print 4 bytes in octal.
q 2 Print in signed octal.
Q 4 Print long signed octal.
d 2 Print in decimal.
D 4 Print long decimal.
x 2 Print 2 bytes in hexadecimal.
X 4 Print 4 bytes in hexadecimal.
u 2 Print as an unsigned decimal number.
U 4 Print long unsigned decimal.
f 4 Print the 32 bit value as a floating point number.
F 8 Print double floating point.
b 1 Print the addressed byte in octal.
c 1 Print the addressed character.
C 1 Print the addressed character using the following escape
convention. Character values 000 to 040 are printed as @
followed by the corresponding character in the range 0100
to 0140. The character @ is printed as @@.
s n Print the addressed characters until a zero character is
S n Print a string using the @ escape convention. n is the
length of the string including its zero terminator.
Y 4 Print 4 bytes in date format (see ctime(3)).
i n Print as PDP11 instructions. n is the number of bytes
occupied by the instruction. This style of printing
causes variables 1 and 2 to be set to the offset parts of
the source and destination respectively.
a 0 Print the value of dot in symbolic form. Symbols are
checked to ensure that they have an appropriate type as
/ local or global data symbol
? local or global text symbol
= local or global absolute symbol
p 2 Print the addressed value in symbolic form using the same
rules for symbol lookup as a.
t 0 When preceded by an integer tabs to the next appropriate
tab stop. For example, 8t moves to the next 8-space tab
r 0 Print a space.
n 0 Print a newline.
Print the enclosed string.
^ Dot is decremented by the current increment. Nothing is
+ Dot is incremented by 1. Nothing is printed.
- Dot is decremented by 1. Nothing is printed.
If the previous command temporarily incremented dot, make the
increment permanent. Repeat the previous command with a count
[?/]l value mask
Words starting at dot are masked with mask and compared with
value until a match is found. If L is used then the match is
for 4 bytes at a time instead of 2. If no match is found then
dot is unchanged; otherwise dot is set to the matched location.
If mask is omitted then -1 is used.
[?/]w value ...
Write the 2-byte value into the addressed location. If the com-
mand is W, write 4 bytes. Odd addresses are not allowed when
writing to the subprocess address space.
[?/]m b1 e1 f1[?/]
New values for (b1, e1, f1) are recorded. If less than three
expressions are given then the remaining map parameters are left
unchanged. If the `?' or `/' is followed by `*' then the second
segment (b2,e2,f2) of the mapping is changed. If the list is
terminated by `?' or `/' then the file (objfil or corfil respec-
tively) is used for subsequent requests. (So that, for example,
`/m?' will cause `/' to refer to objfil.)
>>name Dot is assigned to the variable or register named.
! A shell is called to read the rest of the line following `!'.
Miscellaneous commands. The available modifiers are:
<<f Read commands from the file f and return.
>>f Send output to the file f, which is created if it does
r Print the general registers and the instruction addressed
by pc. Dot is set to pc.
f Print the floating registers in single or double length.
If the floating point status of ps is set to double (0200
bit) then double length is used anyway.
b Print all breakpoints and their associated counts and
a ALGOL 68 stack backtrace. If address is given then it is
taken to be the address of the current frame (instead of
r4). If count is given then only the first count frames
c C stack backtrace. If address is given then it is taken
as the address of the current frame (instead of r5). If
C is used then the names and (16 bit) values of all auto-
matic and static variables are printed for each active
function. If count is given then only the first count
frames are printed.
e The names and values of external variables are printed.
w Set the page width for output to address (default 80).
s Set the limit for symbol matches to address (default
o All integers input are regarded as octal.
d Reset integer input as described in EXPRESSIONS.
q Exit from adb.
v Print all non zero variables in octal.
m Print the address map.
Manage a subprocess. Available modifiers are:
bc Set breakpoint at address. The breakpoint is executed
count-1 times before causing a stop. Each time the
breakpoint is encountered the command c is executed. If
this command sets dot to zero then the breakpoint causes
d Delete breakpoint at address.
r Run objfil as a subprocess. If address is given explic-
itly then the program is entered at this point; otherwise
the program is entered at its standard entry point.
count specifies how many breakpoints are to be ignored
before stopping. Arguments to the subprocess may be sup-
plied on the same line as the command. An argument
starting with < or > causes the standard input or output
to be established for the command. All signals are
turned on on entry to the subprocess.
cs The subprocess is continued with signal s c s, see sig-
nal(2). If address is given then the subprocess is con-
tinued at this address. If no signal is specified then
the signal that caused the subprocess to stop is sent.
Breakpoint skipping is the same as for r.
ss As for c except that the subprocess is single stepped
count times. If there is no current subprocess then obj-
fil is run as a subprocess as for r. In this case no
signal can be sent; the remainder of the line is treated
as arguments to the subprocess.
k The current subprocess, if any, is terminated.
Adb provides a number of variables. Named variables are set initially
by adb but are not used subsequently. Numbered variables are reserved
for communication as follows.
0 The last value printed.
1 The last offset part of an instruction source.
2 The previous value of variable 1.
On entry the following are set from the system header in the corfil.
If corfil does not appear to be a core file then these values are set
b The base address of the data segment.
d The data segment size.
e The entry point.
m The `magic' number (0405, 0407, 0410 or 0411).
s The stack segment size.
t The text segment size.
The address in a file associated with a written address is determined
by a mapping associated with that file. Each mapping is represented by
two triples (b1, e1, f1) and (b2, e2, f2) and the file address corre-
sponding to a written address is calculated as follows.
b1<=address<e1 => file address=address+f1-b1, otherwise,
b2<=address<e2 => file address=address+f2-b2,
otherwise, the requested address is not legal. In some cases (e.g. for
programs with separated I and D space) the two segments for a file may
overlap. If a ? or / is followed by an * then only the second triple
The initial setting of both mappings is suitable for normal a.out and
core files. If either file is not of the kind expected then, for that
file, b1 is set to 0, e1 is set to the maximum file size and f1 is set
to 0; in this way the whole file can be examined with no address trans-
So that adb may be used on large files all appropriate values are kept
as signed 32 bit integers.
ptrace(2), a.out(5), core(5)
`Adb' when there is no current command or format. Comments about inac-
cessible files, syntax errors, abnormal termination of commands, etc.
Exit status is 0, unless last command failed or returned nonzero sta-
A breakpoint set at the entry point is not effective on initial entry
to the program.
When single stepping, system calls do not count as an executed instruc-
Local variables whose names are the same as an external variable may
foul up the accessing of the external.