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ADB(1)                                                                  ADB(1)



NAME
       adb - debugger

SYNOPSIS
       adb [-w] [ objfil [ corfil ] ]

DESCRIPTION
       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
       programs.

       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
       expressions.

       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.

EXPRESSIONS
       .      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.

       integer
              An octal number if integer begins with a 0; a hexadecimal number
              if preceded by #; otherwise a decimal number.

       integer.fraction
              A 32 bit floating point number.

       'cccc' The ASCII value of up to 4 characters.  \ may be used to  escape
              a '.

       < 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.

       _ symbol
              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.

       routine.name
              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.

       Monadic operators

       *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
       operators.

       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.

COMMANDS
       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
                     reached.
              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
                     indicated below.

                /  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
                     stop.
              r 0    Print a space.
              n 0    Print a newline.
              "..." 0
                     Print the enclosed string.
              ^      Dot is decremented by the current increment.  Nothing  is
                     printed.
              +      Dot is incremented by 1.  Nothing is printed.
              -      Dot is decremented by 1.  Nothing is printed.

       newline
              If  the  previous  command temporarily incremented dot, make the
              increment permanent.  Repeat the previous command with  a  count
              of 1.

       [?/]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 `!'.

       $modifier
              Miscellaneous commands.  The available modifiers are:

              <&lt;f     Read commands from the file f and return.
              >&gt;f     Send  output  to  the file f, which is created if it does
                     not exist.
              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
                     commands.
              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
                     are printed.
              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
                     255).
              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.

       :modifier
              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
                     a stop.

              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.

VARIABLES
       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
       from objfil.

       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.

ADDRESSES
       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
       is used.

       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-
       lation.

       So  that adb may be used on large files all appropriate values are kept
       as signed 32 bit integers.

FILES
       /dev/mem
       /dev/swap
       a.out
       core

SEE ALSO
       ptrace(2), a.out(5), core(5)

DIAGNOSTICS
       `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-
       tus.

BUGS
       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-
       tion.
       Local  variables  whose  names are the same as an external variable may
       foul up the accessing of the external.



                                                                        ADB(1)