.\" @(#)adb.ms 6.1 (Berkeley) 5/7/86
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.....TM "77-8234-11 77-1273-10" "49170-220 39199" "40952-1 39199-11"
A Tutorial Introduction to ADB
Debugging tools generally provide a wealth of information
about the inner workings of programs.
These tools have been available on
that result from aborted programs.
A new debugging program, ADB, provides enhanced capabilities
to examine "core" and other program files in a
variety of formats, run programs with embedded breakpoints and patch files.
ADB is an indispensable but complex tool for debugging crashed systems and/or
This document provides an introduction to ADB with examples of its use.
It explains the various formatting options,
techniques for debugging C programs, examples of printing
file system information and patching.
ADB is a new debugging program that is
It provides capabilities to look at
``core'' files resulting from aborted programs, print output in a
variety of formats, patch files, and run programs
with embedded breakpoints.
This document provides examples of
the more useful features of ADB.
The reader is expected to be
familiar with the basic commands on
language, and with References 1, 2 and 3.
is an executable UNIX file and
Many times this will look like:
The filename minus (\-) means ignore this argument as in:
ADB has requests for examining locations in either file.
request examines the contents of
The general form of these requests is:
ADB maintains a current address, called dot,
similar in function to the current pointer in the UNIX editor.
When an address is entered, the current address is set to that location,
sets dot to octal 126 and prints the instruction
prints 10 decimal numbers starting at dot.
Dot ends up referring to the address of the last item printed.
When used with the \fB?\fP or \fB/\fP requests,
the current address can be advanced by typing newline; it can be decremented
Addresses are represented by
Expressions are made up from decimal, octal, and hexadecimal integers,
and symbols from the program under test.
These may be combined with the operators +, \-, *, % (integer division),
& (bitwise and), | (bitwise inclusive or), # (round up
to the next multiple), and ~ (not).
(All arithmetic within ADB is 32 bits.)
When typing a symbolic address for a C program,
ADB will recognize both forms.
To print data, a user specifies a collection of letters and characters
that describe the format of the printout.
Formats are "remembered" in the sense that typing a request without one
will cause the new printout to appear in the previous format.
The following are the most commonly used format letters.
\fB b \fPone byte in octal
\fB c \fPone byte as a character
\fB o \fPone word in octal
\fB d \fPone word in decimal
\fB f \fPtwo words in floating point
\fB i \fPPDP 11 instruction
\fB s \fPa null terminated character string
\fB a \fPthe value of dot
\fB u \fPone word as unsigned integer
\fB r \fPprint a blank space
(Format letters are also available for "long" values,
for example, `\fBD\fR' for long decimal, and `\fBF\fP' for double floating point.)
For other formats see the ADB manual.
The general form of a request is:
address,count command modifier
which sets `dot' to \fIaddress\fP
The following table illustrates some general ADB command meanings:
\fB ? \fPPrint contents from \fIa.out\fP file
\fB / \fPPrint contents from \fIcore\fP file
\fB = \fPPrint value of "dot"
\fB : \fPBreakpoint control
\fB $ \fPMiscellaneous requests
\fB ; \fPRequest separator
ADB catches signals, so a user cannot use a quit signal to exit from ADB.
The request $q or $Q (or cntl-D) must be used
Consider the C program in Figure 1.
The program is used to illustrate a common error made by
The object of the program is to change the
lower case "t" to upper case in the string pointed to by
and then write the character string to the file indicated by
The bug shown is that the character "T"
instead of the string pointed to by
Executing the program produces a core file because of an out of bounds memory reference.
The first debugging request:
is used to give a C backtrace through the
only one function (\fImain\fR) was called and the
Both of these values look
reasonable; 02 = two arguments, 0177762 = address on stack
is used to give a C backtrace plus an interpretation
of all the local variables in each function and their
The value of the variable
was declared as a character.
prints out the registers including the program
counter and an interpretation of the instruction at that
prints out the values of all external variables.
A map exists for each file
file is referenced by \fB?\fP whereas the map for
file is referenced by \fB/\fP.
Furthermore, a good rule of thumb is to use \fB?\fP for
instructions and \fB/\fP for data when looking at programs.
To print out information about the maps type:
This produces a report of the contents of the maps.
More about these maps later.
In our example, it is useful to see the
contents of the string pointed to by
and print the information as a character string.
This printout clearly shows that the character buffer
was incorrectly overwritten and helps identify the error.
Printing the locations around
shows that the buffer is unchanged
but that the pointer is destroyed.
Using ADB similarly, we could print information about the
image value of the argument
prints the octal values of the three consecutive
Note that these values are the addresses of the arguments
prints the ASCII value of the first argument.
Another way to print this value would have been
The " means ditto which remembers the last address
typed, in this case \fImain.argc\fP ; the \fB*\fP instructs ADB to use the address field of the
prints the current address (not its contents) in octal which has been set to the address of the first argument.
The current address, dot, is used by ADB to
"remember" its current location.
to reference locations relative to the current
Consider the C program illustrated in
This program calls functions
until the stack is exhausted and a core image is produced.
Again you can enter the debugger via:
file and core image file respectively.
will fill a page of backtrace references to
Figure 4 shows an abbreviated list (typing
will terminate the output and bring you back to ADB request level).
prints the five most recent activations.
Notice that each function
(\fIf,g,h\fP) has a counter
of the number of times it was called.
prints the decimal value of the counter for the function
To print the value of an automatic variable,
for example the decimal value of
in the last call of the function
It is currently not possible in the exported version to print stack frames other than the most recent activation of a function.
Therefore, a user can print everything with
\fB$C\fR or the occurrence of a variable in the most recent call of a function.
It is possible with the \fB$C\fR request, however, to print the stack frame
starting at some address as \fBaddress$C.\fR
Consider the C program in Figure 5.
This program, which changes tabs into blanks, is adapted from
by Kernighan and Plauger, pp. 18-27.
We will run this program under the control of ADB (see Figure 6a) by:
Breakpoints are set in the program as:
set breakpoints at the start of these functions.
C does not generate statement labels.
Therefore it is currently not possible to plant breakpoints at locations
other than function entry points without a knowledge of the code
generated by the C compiler.
The above addresses are entered as
so that they will appear in any
C backtrace since the first instruction of each function is a call
Note that some of the functions are from the C library.
To print the location of breakpoints one types:
times before causing a stop.
field indicates the ADB requests to be executed each time the breakpoint is encountered.
By displaying the original instructions at the function
the breakpoint is set after the jsr to the C save routine.
We can display the instructions using the ADB request:
This request displays five instructions starting at
with the addresses of each location displayed.
which displays the instructions with only the starting address.
Notice that we accessed the addresses from the
file with the \fB?\fP command.
In general when asking for a printout of multiple items,
ADB will advance the current address the number of
bytes necessary to satisfy the request; in the above
example five instructions were displayed and the current address was
advanced 18 (decimal) bytes.
To run the program one simply types:
To delete a breakpoint, for instance the entry to the function
To continue execution of the program from the breakpoint type:
Once the program has stopped (in this case at the breakpoint for
ADB requests can be used to display the contents of memory.
to display a stack trace, or:
to print three lines of 8 locations each from the array called
By this time (at location
has been called and should have set a one in every eighth location of
Advanced Breakpoint Usage
We continue execution of the program with:
is called three times and the contents of the variable
The single character on the left hand edge is the output from the C program.
On the third occurrence of
We can look at the full buffer of characters by typing:
When we continue the program with:
we hit our first breakpoint at
since there is a tab following the
will occur until the program has changed the tab into equivalent blanks.
we can remove the breakpoint at that location by:
If the program is continued with:
it resumes normal execution after ADB prints
The UNIX quit and interrupt signals
act on ADB itself rather than on the program being debugged.
If such a signal occurs then the program being debugged is stopped and control is returned to ADB.
The signal is saved by ADB and is passed on to the test program if:
This can be useful when testing interrupt
The signal is not passed on to the test program if:
Now let us reset the breakpoint at
and display the instructions located there when we reach the breakpoint.
settab+4:b settab,5?ia \fR*
* Owing to a bug in early versions of ADB (including the
version distributed in Generic 3 UNIX) these statements
\fBsettab+4:b settab,5?ia;0\fR
settab+4:b settab,5?ia; ptab/o;0
Note that \fB;0\fR will set dot to zero and stop at the breakpoint.
It is also possible to execute the ADB requests for each occurrence of the breakpoint but
only stop after the third occurrence by typing:
This request will print the local variable
at each occurrence of the breakpoint.
The semicolon is used to separate multiple ADB requests on a single line.
setting a breakpoint causes the value of dot to be changed;
executing the program under ADB does not change dot.
will print the last thing dot was set to
(in the example \fIfopen+4\fP)
the current location (\fIsettab+4\fP)
at which the program is executing.
A breakpoint can be overwritten without first deleting the old breakpoint.
settab+4:b settab,5?ia; ptab/o \fR*
could be entered after typing the above requests.
Now the display of breakpoints:
shows the above request for the
is encountered the ADB requests are executed.
Note that the location at
has been changed to plant the breakpoint;
all the other locations match their original value.
we can follow the execution of each function by planting non-stopping
We call ADB with the executable program of Figure 3 as follows:
Suppose we enter the following breakpoints:
h+4:b hcnt/d; h.hi/; h.hr/
g+4:b gcnt/d; g.gi/; g.gr/
f+4:b fcnt/d; f.fi/; f.fr/
Each request line indicates that the variables are printed in decimal
(by the specification \fBd\fR).
Since the format is not changed, the \fBd\fR can be left off all but
The output in Figure 7 illustrates two points.
First, the ADB requests in the breakpoint line are not
examined until the program under
That means any errors in those ADB requests is not detected until run time.
At the location of the error ADB stops running the program.
The second point is the way ADB handles register variables.
ADB uses the symbol table to address variables.
Register variables, like \fIf.fr\fR above, have pointers to uninitialized
Therefore the message "symbol not found".
Another way of getting at the data in this example is to print
the variables used in the call as:
f+4:b fcnt/d; f.a/; f.b/; f.fi/
g+4:b gcnt/d; g.p/; g.q/; g.gi/
The operator / was used instead of ?
to read values from the \fIcore\fP file.
The output for each function, as shown in Figure 7, has the same format.
For the function \fIf\fP, for example, it shows the name and value of the
It also shows the address on the stack and value of the
Notice that the addresses on the stack will continue to decrease
until no address space is left for program execution
at which time (after many pages of output)
the program under test aborts.
A display with names would be produced by requests like the following:
f+4:b fcnt/d; f.a/"a="d; f.b/"b="d; f.fi/"fi="d
In this format the quoted string is printed literally and the \fBd\fP
produces a decimal display of the variables.
The results are shown in Figure 7.
Other Breakpoint Facilities
Arguments and change of standard input and output are passed to a program as:
:r arg1 arg2 ... <infile >outfile
kills any existing program under test and
The program being debugged can be single stepped
If necessary, this request will start up the program being
debugged and stop after executing
ADB allows a program to be entered at a specific address
The count field can be used to skip the first \fIn\fR breakpoints as:
may also be used for skipping the first \fIn\fR breakpoints
when continuing a program.
A program can be continued at an address different from the breakpoint by:
The program being debugged runs as a separate process and can be killed by:
UNIX supports several executable file formats. These are used to tell
the loader how to load the program file. File type 407
is the most common and is generated by a C compiler invocation such as
A 410 file is produced by a C compiler command of the form \fBcc -n pgm.c\fP,
whereas a 411 file is produced by \fBcc -i pgm.c\fP.
ADB interprets these different file formats and
provides access to the different segments through a set of maps (see Figure 8).
In 407 files, both text (instructions) and data are intermixed.
This makes it impossible for ADB to differentiate data from
instructions and some of the printed symbolic addresses look incorrect;
for example, printing data addresses as offsets from routines.
In 410 files (shared text), the instructions are separated from data and
\fB?*\fR accesses the data part of the \fIa.out\fP file.
The \fB?* \fP request tells ADB to use the second part of the
Accessing data in the \fIcore\fP file shows
the data after it was modified by the execution of the program.
Notice also that the data segment may have grown during
In 411 files (separated I & D space), the
instructions and data are also separated.
case, since data is mapped through a separate set of segmentation
registers, the base of the data segment is also relative to address zero.
In this case since the addresses overlap it is necessary to use
the \fB?*\fR operator to access the data space of the \fIa.out\fP file.
In both 410 and 411 files the corresponding
core file does not contain the program text.
Figure 9 shows the display of three maps
for the same program linked as a 407, 410, 411 respectively.
The b, e, and f fields are used by ADB to map
addresses into file addresses.
length of the header at the beginning of the file (020 bytes
for an \fIa.out\fP file and 02000 bytes for a \fIcore\fP file).
The "f2" field is the displacement from the beginning of the file to the data.
For a 407 file with mixed text and data this is the
same as the length of the header; for 410 and 411 files this
is the length of the header plus the size of the text portion.
The "b" and "e" fields are the starting and ending locations
Given an address, A, the location in
the file (either \fIa.out\fP or \fIcore\fP) is calculated as:
b1\(<=A\(<=e1 =\h'-.5m'> file address = (A\-b1)+f1
b2\(<=A\(<=e2 =\h'-.5m'> file address = (A\-b2)+f2
A user can access locations by using the ADB defined variables.
The \fB$v\fR request prints the variables initialized by ADB:
b base address of data segment
d length of the data segment
m execution type (407,410,411)
In Figure 9 those variables not present are zero.
Use can be made of these variables by expressions such as:
Similarly the value of the variable can be changed by an assignment request
that sets \fBb\fP to octal 2000.
These variables are useful to know if the file under examination
is an executable or \fIcore\fP image file.
ADB reads the header of the \fIcore\fP image file to find the
values for these variables.
If the second file specified does not
seem to be a \fIcore\fP file, or if it is missing then the header of
the executable file is used instead.
It is possible with ADB to combine formatting requests
to provide elaborate displays.
Below are several examples.
prints 4 octal words followed by their ASCII interpretation
from the data space of the core image file.
Broken down, the various request pieces mean:
<b The base address of the data segment.
<b,\-1 Print from the base address to the end of file.
A negative count is used here and elsewhere to loop indefinitely
or until some error condition (like end of file) is detected.
The format \fB4o4^8Cn\fR is broken down as follows:
4o Print 4 octal locations.
4^ Backup the current address 4 locations (to the original start of the field).
8C Print 8 consecutive characters using an escape convention;
each character in the range 0 to 037 is printed as @ followed by the corresponding character in the range 0140 to 0177.
could have been used instead to allow the printing to stop
at the end of the data segment (<d provides the data segment size in bytes).
The formatting requests can be combined with ADB's ability
to read in a script to produce a core image dump script.
to read in a script file,
An example of such a script is:
=3n"C External Variables"
The request \fB120$w\fP sets the width of the output to
(normally, the width is 80 characters).
ADB attempts to print addresses as:
The request \fB4095$s\fP increases the maximum permissible offset
to the nearest symbolic address from 255 (default) to 4095.
The request \fB=\fP can be used to print literal strings.
headings are provided in this
with requests of the form:
that spaces three lines and prints the literal
The request \fB$v\fP prints all non-zero ADB variables (see Figure 8).
sets the maximum offset for symbol matches to zero thus
suppressing the printing of symbolic labels in favor
Note that this is only done for the printing of the data segment.
prints a dump from the base of the data segment to the end of file
with an octal address field and eight octal numbers per line.
Figure 11 shows the results of some formatting requests
on the C program of Figure 10.
As another illustration (Figure 12) consider a set of requests to dump
the contents of a directory (which is made up
of an integer \fIinumber\fP followed by a 14 character name):
In this example, the \fBu\fP prints the \fIinumber\fP as an unsigned decimal integer,
the \fB8t\fP means that ADB will space to the next
multiple of 8 on the output line, and the \fB14c\fP prints the 14 character file name.
Similarly the contents of the \fIilist\fP of a file system, (e.g. /dev/src,
on UNIX systems distributed by the UNIX Support Group;
Manual Section V) could be dumped with the following set of
<b,\-1?"flags"8ton"links,uid,gid"8t3bn",size"8tbrdn"addr"8t8un"times"8t2Y2na
In this example the value of the base for the map was changed
to 02000 (by saying \fB?m<b\fR) since that is the start of an \fIilist\fP within a file system.
An artifice (\fBbrd\fP above) was used to print the 24 bit size field
as a byte, a space, and a decimal integer.
The last access time and last modify time are printed with the
Figure 12 shows portions of these requests as applied to a directory
ADB may be used to convert values from one representation to
which is the octal, decimal and hexadecimal representations
The format is remembered so that typing
subsequent numbers will print them in the given formats.
Character values may be converted similarly, for example:
It may also be used to evaluate expressions but be
warned that all binary operators have
the same precedence which is lower than that for unary operators.
Patching files with ADB is accomplished with the
\fBw\fP or \fBW\fP, request (which is not like the \fIed\fP editor write command).
This is often used in conjunction with the
In general, the request syntax for \fBl\fP and \fBw\fP are similar as follows:
The request \fBl\fP is used to match on two bytes, \fBL\fP is used for
The request \fBw\fP is used to write two bytes, whereas
\fBW\fP writes four bytes.
The \fBvalue\fP field in either
Therefore, decimal and octal numbers, or character strings are supported.
In order to modify a file, ADB must be called as:
When called with this option,
are created if necessary and opened for both reading and writing.
For example, consider the C program shown in Figure 10.
We can change the word "This" to "The " in the executable file
for this program, \fIex7\fP, by using the following requests:
The request \fB?l\fP starts at dot and stops at the first match of "Th"
having set dot to the address of the location found.
Note the use of \fB?\fP to write to the
The form \fB?*\fP would have been used for a 411 file.
request will be typed as:
and locates the first occurrence of "Th" and print the entire string.
Execution of this ADB request will set dot to the address of the
As another example of the utility of the patching facility,
consider a C program that has an internal logic flag.
The flag could be set by the user through ADB and the program run.
The \fB:s\fR request is normally used to single step through a process
or start a process in single step mode.
with arguments \fBarg1\fP and \fBarg2\fP.
If there is a subprocess running ADB writes to it rather than to the file
so the \fBw\fP request causes \fIflag\fP to be changed in the memory of the subprocess.
Below is a list of some strange things that users
Function calls and arguments are put on the stack by the C
Putting breakpoints at the entry point to routines
means that the function appears not to have been called
When printing addresses, ADB uses
either text or data symbols from the \fIa.out\fP file.
This sometimes causes unexpected symbol names to be printed
with data (e.g. \fIsavr5+022\fP).
\fB?\fR is used for text (instructions)
ADB cannot handle C register variables
in the most recently activated function.
The authors are grateful for the thoughtful comments
on how to organize this document
from R. B. Brandt, E. N. Pinson and B. A. Tague.
D. M. Ritchie made the system changes necessary to accommodate
tracing within ADB. He also participated in discussions
during the writing of ADB.
His earlier work with DB and CDB led to many of the
.SG MH-8234-JFM/1273-SRB-unix
D. M. Ritchie and K. Thompson,
``The UNIX Time-Sharing System,''
B. W. Kernighan and D. M. Ritchie,
The C Programming Language,
K. Thompson and D. M. Ritchie,
UNIX Programmer's Manual - 7th Edition,
B. W. Kernighan and P. J. Plauger,
.ta .5i 1i 1.5i 2i 2.5i 3i 3.5i 4i 4.5i 5i
Figure 1: C program with pointer bug
char *charp "this is a sentence.";
printf("Input file missing\\n");
if((fcreat(argv[1],obuf)) < 0){
printf("%s : not found\\n", argv[1]);
printf("debug 1 %s\\n",charp);
Figure 2: ADB output for C program of Figure 1
~main+0152: mov _obuf,(sp)
b1 = 0 e1 = 02360 f1 = 020
b2 = 0 e2 = 02360 f2 = 020
b1 = 0 e1 = 03500 f1 = 02000
b2 = 0175400 e2 = 0200000 f2 = 05500
0124: TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
\1dL
\ 3x
\7f \ 3N
\1dh
\ 4@
\1dx
\7f&
\10_
_charp+02: this is a sentence.
_charp+026: Input file missing
0177762: 0177770 0177776 0177777
0177762: 0177770 0177776 0177777
Figure 3: Multiple function C program for stack trace illustration
Figure 4: ADB output for C program of Figure 3
Figure 5: C program to decode tabs
settab(ptab); /*Set initial tab stops */
if(fopen(input,ibuf) < 0) {
printf("%s : not found\\n",input);
while((c = getc(ibuf)) != \(mi1) {
case \(fm\\t\(fm: /* TAB */
while(tabpos(col) != YES) {
putchar(\(fm \(fm); /* put BLANK */
case \(fm\\n\(fm: /*NEWLINE */
/* Tabpos return YES if col is a tab stop */
/* Settab - Set initial tab stops */
for(i = 0; i<= MAXLINE; i++)
(i%TABSP) ? (tabs[i] = NO) : (tabs[i] = YES);
Figure 6a: ADB output for C program of Figure 5
~settab+06: clr 0177770(r5)
~settab+012: cmp $0120,0177770(r5)
~settab+020: blt ~settab+076
breakpoint ~settab+04: tst \(mi(sp)
breakpoint _fopen+04: mov 04(r5),nulstr+012
Figure 6b: ADB output for C program of Figure 5
breakpoint _getc+04: mov 04(r5),r1
__cleanu+0202: This is a test of
breakpoint ~tabpos+04: cmp $0120,04(r5)
settab+4:b settab,5?ia; 0
settab+4:b settab,5?ia; ptab/o; 0
1 ~settab+04 settab,5?ia;ptab?o;0
~settab+06: clr 0177770(r5)
~settab+012: cmp $0120,0177770(r5)
~settab+020: blt ~settab+076
Figure 7: ADB output for C program with breakpoints
h+4:b hcnt/d; h.hi/; h.hr/
g+4:b gcnt/d; g.gi/; g.gr/
f+4:b fcnt/d; f.fi/; f.fr/
f+4:b fcnt/d; f.a/; f.b/; f.fi/
g+4:b gcnt/d; g.p/; g.q/; g.gi/
h+4:b hcnt/d; h.x/; h.y/; h.hi/
f+4:b fcnt/d; f.a/"a = "d; f.b/"b = "d; f.fi/"fi = "d
g+4:b gcnt/d; g.p/"p = "d; g.q/"q = "d; g.gi/"gi = "d
h+4:b hcnt/d; h.x/"x = "d; h.y/"h = "d; h.hi/"hi = "d
Figure 8: ADB address maps
.ta 1.6i +2.80i +.2i +1.55i
.ta +.8i +2.85i +0.4i +1.1i
.ta +.85i +1.6i +.35i +1.1i
411 files (separated I and D space)
.ta .75i 1.5i 3.5i 4.5i 5.5i
d length of data D D\(miB D
Figure 9: ADB output for maps
b1 = 0 e1 = 0256 f1 = 020
b2 = 0 e2 = 0256 f2 = 020
b1 = 0 e1 = 0300 f1 = 02000
b2 = 0175400 e2 = 0200000 f2 = 02300
b1 = 0 e1 = 0200 f1 = 020
b2 = 020000 e2 = 020116 f2 = 0220
b1 = 020000 e1 = 020200 f1 = 02000
b2 = 0175400 e2 = 0200000 f2 = 02200
b1 = 0 e1 = 0200 f1 = 020
b2 = 0 e2 = 0116 f2 = 0220
b1 = 0 e1 = 0200 f1 = 02000
b2 = 0175400 e2 = 0200000 f2 = 02200
Figure 10: Simple C program for illustrating formatting and patching
char str1[] "This is a character string";
char str2[] "This is the second character string";
Figure 11: ADB output illustrating fancy formats
020000: 0 064124 071551 064440 020163 020141 064143 071141
_str1+016: 061541 062564 020162 072163 064562 063556 0 02
_number: 0710 0 02322 040240 0 064124 071551 064440
_str2+06: 020163 064164 020145 062563 067543 062156 061440 060550
_str2+026: 060562 072143 071145 071440 071164 067151 0147 0
savr5+02: 0 0 0 0 0 0 0 0
020000: 0 064124 071551 064440 @\`@\`This i
020163 020141 064143 071141 s a char
061541 062564 020162 072163 acter st
064562 063556 0 02 ring@\`@\`@b@\`
_number: 0710 0 02322 040240 H@a@\`@\`R@d @@
0 064124 071551 064440 @\`@\`This i
020163 064164 020145 062563 s the se
067543 062156 061440 060550 cond cha
060562 072143 071145 071440 racter s
071164 067151 0147 0 tring@\`@\`@\`
0 0 0 0 @\`@\`@\`@\`@\`@\`@\`@\`
0 0 0 0 @\`@\`@\`@\`@\`@\`@\`@\`
020000: 0 064124 071551 064440 This i
_str1+06: 020163 020141 064143 071141 s a char
_str1+016: 061541 062564 020162 072163 acter st
_str1+026: 064562 063556 0 02 ring
\ 2
_number: 0710 0 02322 040240 HR
_fpt+02: 0 064124 071551 064440 This i
_str2+06: 020163 064164 020145 062563 s the se
_str2+016: 067543 062156 061440 060550 cond cha
_str2+026: 060562 072143 071145 071440 racter s
_str2+036: 071164 067151 0147 0 tring
Figure 12: Directory and inode dumps
b1 = 02000 e1 = 0100000000 f1 = 0
<b,\(mi1?"flags"8ton"links,uid,gid"8t3bn"size"8tbrdn"addr"8t8un"times"8t2Y2na
links,uid,gid 0163 0164 0141
addr 28770 8236 25956 27766 25455 8236 25956 25206
times 1976 Feb 5 08:34:56 1975 Dec 28 10:55:15
links,uid,gid 012 0163 0164
addr 8308 30050 8294 25130 15216 26890 29806 10784
times 1976 Aug 17 12:16:51 1976 Aug 17 12:16:51
links,uid,gid 011 0162 0145
addr 25972 8306 28265 8308 25642 15216 2314 25970
times 1977 Apr 2 08:58:01 1977 Feb 5 10:21:44
.IP "\fB? \fIformat\fR" .7i
print from \fIa.out\fR file according to \fIformat\fR
.IP "\fB/ \fIformat\fR" .7i
print from \fIcore\fR file according to \fIformat\fR
.IP "\fB= \fIformat\fR" .7i
print the value of \fIdot\fR
write expression into \fIa.out\fR file
write expression into \fIcore\fR file
locate expression in \fIa.out\fR file
b) breakpoint and program control
\fB:b\fR set breakpoint at \fIdot\fR
\fB:c\fR continue running program
\fB:d\fR delete breakpoint
\fB:k\fR kill the program being debugged
\fB:r\fR run \fIa.out\fR file under ADB control
c) miscellaneous printing
\fB$b\fR print current breakpoints
\fB$e\fR external variables
\fB$f\fR floating registers
\fB$m\fR print ADB segment maps
\fB$r\fR general registers
\fB$s\fR set offset for symbol match
\fB$v\fR print ADB variables
\fB$w\fR set output line width
\fB!\fR call \fIshell\fP to read rest of line
e) assignment to variables
\fB>\fIname\fR assign dot to variable or register \fIname\fR
\fBb \fRone byte in octal
\fBc \fRone byte as a character
\fBd \fRone word in decimal
\fBf \fRtwo words in floating point
\fBi \fRPDP 11 instruction
\fBo \fRone word in octal
\fBr \fRprint a blank space
\fBs \fRa null terminated character string
\fIn\fBt \fRmove to next \fIn\fR space tab
\fBu \fRone word as unsigned integer
\fBdecimal integer \fRe.g. 256
\fBoctal integer \fRe.g. 0277
\fBhexadecimal \fRe.g. #ff
\fBsymbols \fRe.g. flag _main main.argc
\fBregisters \fRe.g. <pc <r0
\fB(expression) \fRexpression grouping
\fB#\fP round up to the next multiple
\v'.25m'\s+2\fB~\fP\s0\v'-.25m' not
\fB*\fR contents of location
\fB\(mi\fR integer negate