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ADB(1)											   ADB(1)

NAME
       adb - debugger (2BSD)

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

DESCRIPTION
       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.

       The  -k	option	makes adb do UNIX kernel memory mapping; it should be used when core is a
       UNIX crash dump or /dev/mem.

       The -I option specifies a directory where files to be read with $< or $<< (see below) will
       be sought; the default is /usr/share/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.  This default interpretation of integers may be changed
	      via the $o and $d commands.

       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 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 those printed by the $r command.

       symbol A symbol is a sequence of upper or lower case letters, underscores or  digits,  not
	      starting with a digit.  The backslash character \ may be used to escape other char-
	      acters.  The value of the symbol is taken from the symbol table in objfil.  An ini-
	      tial  _ or ~ will be prepended to symbol if needed.  If the symbol is a text symbol
	      and objfil is an overlay type, the default is  ~symbol,  which  is  the  subroutine
	      itself, not the entry interface in the base segment.

       _ symbol
	      In  C, the `true name' of an external symbol begins with _.  It may be necessary to
	      utter this name to distinguish it from internal or hidden variables of  a  program.
	      For  a  subroutine  in an overlay, ~symbol is the actual subroutine, and _symbol is
	      the entry point in the base segment (the "thunk").  Note that to explicitly specify
	      the local name, the ~ must be preceeded by a backslash, since ~ is the bitwise com-
	      plement operator: \~symbol must be typed.

       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 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.

COMMANDS
       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.   dot
	    is incremented by the sum of the increments for each format letter (q.v.).

       /f   Locations starting at address in corfil are printed according to the format f and dot
	    is incremented as for `?'.

       =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 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.   the
		     standard  escape  convention  where control characters are printed as ^X and
		     the delete character is printed as ^?.
	      s n    Print the addressed characters until a zero character is reached.
	      S n    Print a string using the ^X escape convention  (see  C  above).   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	machine  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 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 last 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 (/bin/sh) is called to read the rest of the line following `!'.

       $modifier
	      Miscellaneous commands.  The available modifiers are:

	      <f     Read commands from the file f.  If this command is executed in a file,  fur-
		     ther  commands in the file are not seen.  If f is omitted, the current input
		     stream is terminated.  If a count is given, and is zero, the command will be
		     ignored.	The  value  of	the count will be placed in variable 9 before the
		     first command in f is executed.
	      <<f    Similar to < except it can be used in a file of commands without causing the
		     file  to  be  closed.  Variable 9 is saved during the execution of this com-
		     mand, and restored when it completes.  There is a (small)	finite	limit  to
		     the number of << files that can be open at once.
	      >f     Append output to the file f, which is created if it does not exist.  If f is
		     omitted, output is returned to the terminal.
	      ?      Print process id, the signal which caused stoppage or termination,  as  well
		     as the registers as $r.  This is the default if modifier is omitted.
	      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 the contents of the frame-pointer register.  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.

       :modifier
	      Manage a subprocess.  Available modifiers are:

	      bc     Set breakpoint at address.  If objfil is overlaid	and  address  is  in  the
		     overlay region, the breakpoint is set in the overlay of the symbol mentioned
		     if address was given symbolically, otherwise it is set in the current  over-
		     lay  (that  in variable c).  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 is omitted or sets dot to zero then the break-
		     point causes a stop.

	      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.

	      cs     The  subprocess  is  continued  with signal s, see sigvec(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.

VARIABLES
       Adb  provides a number of variables.  Named variables are set initially by adb but are not
       used subsequently (except for c).  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.
       9      The count on the last $< or $<< command.

       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.
       c      The current overlay.  This is set from corfil, and in turn sets  the  overlay  map.
	      This  variable  and  the map may be changed by referring to other overlays symboli-
	      cally (e.g. by examining text in subroutines in other overlays), using the $r  com-
	      mand (which resets c from the core file), or explicitly (with the command >c).
       d      The data segment size.
       e      The entry point.
       m      The  `magic' number (0405, 0407, 0410, 0411, 0430 or 0431).  The object is overlaid
	      if m is 0430 or 0431.
       o      The sum of the overlay segment sizes (if overlaid).
       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 associ-
       ated  with  that  file.	Each mapping is represented by two or three triples (b1, e1, f1),
       (bo, eo, fo) for overlaid object files, and (b2, e2, f2) and the file address  correspond-
       ing to a written address is calculated as follows.

	b1<=address<e1 => file address=address+f1-b1, otherwise,

       if overlaid,
	bo<=address<eo => file address=address+fo-bo, 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 last triple is used.

       The  initial setting of both mappings is suitable for normal a.out and core files.  If the
       object file is not of the kind expected then, for both files, 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
       integers.

FILES
       a.out
       core

SEE ALSO
       cc(1), ptrace(2), a.out(5), core(5)
       ADB - A Tutorial, S. R. Bourne

DIAGNOSTICS
       `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.

BUGS
       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.
       Local variables cannot be accessed in routines that are in overlays.
       Since no shell is invoked to interpret the arguments of	the  :r  command,  the	customary
       wild-card and variable expansions cannot occur.

3rd Berkeley Distribution		 October 21, 1996				   ADB(1)
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