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ADB(1)											   ADB(1)

       adb - debugger

       adb [-w] [ objfil [ corfil ] ]

       Adb  is	a general purpose debugging program.  It may be used to examine files and to pro-
       vide 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 exam-
       ined.  The default for objfil is a.out.	Corfil is assumed to be a core	image  file  pro-
       duced after executing 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; INTER-
       RUPT 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.

       .      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 a '.

       < name The  value  of name, which is either a variable name or a register name.	Adb main-
	      tains 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, underscores 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 internal 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 corresponding 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.

       Most commands consist of a verb followed by a modifier or list of modifiers.  The  follow-
       ing  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

       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 char-
       acter.  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.   Char-
		     acter values 000 to 040 are printed as @ followed by the corresponding char-
		     acter 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.

	      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 command 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  fol-
	      lowed  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	respectively)  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 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
	      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  automatic  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.

	      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

	      d      Delete breakpoint at address.

	      r      Run objfil as a subprocess.  If address is given explicitly 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 supplied 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 signal(2).  If address is
		     given then the subprocess is continued 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 objfil 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 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.

       The address in a file associated with a written address is determined by a mapping associ-
       ated with that file.  Each mapping is represented by two triples (b1, e1, f1) and (b2, e2,
       f2) and the file address corresponding 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 sep-
       arated 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 translation.

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


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

       `Adb' when there is no current command or format.  Comments about inaccessible files, syn-
       tax errors, abnormal termination of commands, etc.  Exit status is 0, unless last  command
       failed or returned nonzero status.

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

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