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proc(4)				 File Formats			       proc(4)

NAME
       proc - /proc, the process file system

DESCRIPTION
       /proc  is  a  file  system  that	 provides  access to the state of each
       process and light-weight	process	(lwp) in the system. The name of  each
       entry  in  the  /proc  directory	is a decimal number corresponding to a
       process-ID. These entries  are  themselves  subdirectories.  Access  to
       process	state  is  provided  by	additional files contained within each
       subdirectory; the hierarchy is described	more completely	below. In this
       document,  ``/proc  file''  refers  to  a non-directory file within the
       hierarchy rooted	at /proc. The owner of each /proc file	and  subdirec-
       tory is determined by the user-ID of the	process.

       /proc  can  be  mounted on any mount point, in addition to the standard
       /proc mount point, and can be mounted  several  places  at  once.  Such
       additional mounts are allowed in	order to facilitate the	confinement of
       processes to subtrees of	the file system	via chroot(1M) and  yet	 allow
       such processes access to	commands like ps(1).

       Standard	 system	 calls	are  used  to  access  /proc  files:  open(2),
       close(2),  read(2),  and	 write(2)  (including	readv(2),   writev(2),
       pread(2),  and  pwrite(2)).  Most  files	describe process state and can
       only be opened for reading.  ctl	 and  lwpctl  (control)	 files	permit
       manipulation  of	 process  state	and can	only be	opened for writing. as
       (address	space) files contain the image of the running process and  can
       be  opened  for	both  reading  and writing. An open for	writing	allows
       process control;	a read-only open allows	inspection but not control. In
       this  document,	we refer to the	process	as open	for reading or writing
       if any of its associated	/proc files is open for	reading	or writing.

       In general, more	than one process can open the same /proc file  at  the
       same  time.  Exclusive  open is an advisory mechanism provided to allow
       controlling processes to	avoid collisions with each  other.  A  process
       can obtain exclusive control of a target	process, with respect to other
       cooperating processes, if it successfully opens any /proc file  in  the
       target  process for writing (the	as or ctl files, or the	lwpctl file of
       any lwp)	while specifying O_EXCL	in the open(2).	Such an	open will fail
       if  the	target process is already open for writing (that is, if	an as,
       ctl, or lwpctl file is already open for writing). There can be any num-
       ber of concurrent read-only opens; O_EXCL is ignored on opens for read-
       ing. It is recommended that the first open for writing by a controlling
       process	use  the  O_EXCL  flag;	multiple controlling processes usually
       result in chaos.

       If a process opens one of its own /proc files  for  writing,  the  open
       succeeds	 regardless  of	 O_EXCL	 and  regardless of whether some other
       process has the process open for	writing. Self-opens do not count  when
       another process attempts	an exclusive open. (A process cannot exclude a
       debugger	by opening itself for writing and the application of a	debug-
       ger  cannot  prevent a process from opening itself.) All	self-opens for
       writing are forced to be	close-on-exec (see the	F_SETFD	 operation  of
       fcntl(2)).

       Data  may  be transferred from or to any	locations in the address space
       of the traced process by	applying lseek(2) to position the as  file  at
       the  virtual address of interest	followed by read(2) or write(2)	(or by
       using pread(2) or pwrite(2) for the combined operation).	 The  address-
       map  file  /proc/pid/map	 can be	read to	determine the accessible areas
       (mappings) of the address space.	I/O transfers may span contiguous map-
       pings.  An  I/O request extending into an unmapped area is truncated at
       the boundary. A write request beginning at an unmapped virtual  address
       fails with EIO; a read request beginning	at an unmapped virtual address
       returns zero (an	end-of-file indication).

       Information and control	operations  are	 provided  through  additional
       files.  <procfs.h>  contains definitions	of data	structures and message
       formats used with these files. Some of these  definitions  involve  the
       use  of	sets  of flags.	The set	types sigset_t,	fltset_t, and sysset_t
       correspond, respectively, to signal, fault, and	system	call  enumera-
       tions  defined  in  <sys/signal.h>, <sys/fault.h>, and <sys/syscall.h>.
       Each set	type is	large enough to	hold flags for	its  own  enumeration.
       Although	 they are of different sizes, they have	a common structure and
       can be manipulated by these macros:

	      prfillset(&set);		   /* turn on all flags	in set */
	      premptyset(&set);		   /* turn off all flags in set	*/
	      praddset(&set, flag);	   /* turn on the specified flag */
	      prdelset(&set, flag);	   /* turn off the specified flag */
	      r	= prismember(&set, flag);  /* != 0 iff flag is turned on */

       One of prfillset() or premptyset()  must	 be  used  to  initialize  set
       before  it is used in any other operation. flag must be a member	of the
       enumeration corresponding to set.

       Every process contains at least one light-weight	process, or lwp.  Each
       lwp  represents	a flow of execution that is independently scheduled by
       the operating system. All lwps in a process share its address space  as
       well as many other attributes.  Through the use of lwpctl and ctl files
       as described below, it is possible  to  affect  individual  lwps	 in  a
       process or to affect all	of them	at once, depending on the operation.

       When  the process has more than one lwp,	a representative lwp is	chosen
       by the system for certain process status	files and control  operations.
       The  representative  lwp	 is a stopped lwp only if all of the process's
       lwps are	stopped; is stopped on an event	of interest only if all	of the
       lwps are	so stopped (excluding PR_SUSPENDED lwps); is in	a PR_REQUESTED
       stop only if there are no other events of interest  to  be  found;  or,
       failing	everything  else, is in	a PR_SUSPENDED stop (implying that the
       process is deadlocked).	See the	description of	the  status  file  for
       definitions of stopped states. See the PCSTOP control operation for the
       definition of ``event of	interest''.

       The representative lwp remains fixed (it	will be	chosen	again  on  the
       next  operation)	 as  long  as all of the lwps are stopped on events of
       interest	or are in a PR_SUSPENDED stop and the PCRUN control  operation
       is not applied to any of	them.

       When applied to the process control file, every /proc control operation
       that must act on	an lwp uses the	same algorithm to choose which lwp  to
       act  upon. Together with	synchronous stopping (see PCSET), this enables
       a debugger to control a multiple-lwp process using  only	 the  process-
       level status and	control	files if it so chooses.	More fine-grained con-
       trol can	be achieved using the lwp-specific files.

       The system supports two process data  models,  the  traditional	32-bit
       data  model in which ints, longs	and pointers are all 32	bits wide (the
       ILP32 data model), and on some platforms	the 64-bit data	model in which
       longs  and  pointers, but not ints, are 64 bits in width	(the LP64 data
       model). In the LP64 data	model some system data types, notably  size_t,
       off_t, time_t and dev_t,	grow from 32 bits to 64	bits as	well.

       The  /proc  interfaces  described here are available to both 32-bit and
       64-bit controlling processes. However, many operations attempted	 by  a
       32-bit  controlling  process  on	a 64-bit target	process	will fail with
       EOVERFLOW because the address space range of a  32-bit  process	cannot
       encompass  a  64-bit  process or	because	the data in some 64-bit	system
       data type cannot	be compressed to fit  into  the	 corresponding	32-bit
       type  without loss of information. Operations that fail in this circum-
       stance include reading and  writing  the	 address  space,  reading  the
       address-map  file, and setting the target process's registers. There is
       no restriction on operations applied by a 64-bit	process	 to  either  a
       32-bit or a 64-bit target processes.

       The  format of the contents of any /proc	file depends on	the data model
       of the observer (the controlling	process), not on the data model	of the
       target process. A 64-bit	debugger does not have to translate the	infor-
       mation it reads from a /proc file for a 32-bit process from 32-bit for-
       mat  to	64-bit format. However,	it usually has to be aware of the data
       model of	the target process. The	pr_dmodel field	of  the	 status	 files
       indicates the target process's data model.

       To help deal with system	data structures	that are read from 32-bit pro-
       cesses, a 64-bit	controlling program can	be compiled with  the  C  pre-
       processor  symbol  _SYSCALL32  defined  before  system header files are
       included. This makes explicit 32-bit fixed-width	data structures	 (like
       cstruct stat32) visible to the 64-bit program. See types32(3HEAD).

DIRECTORY STRUCTURE
       At  the	top  level, the	directory /proc	contains entries each of which
       names an	existing process in the	system.	These entries  are  themselves
       directories.  Except  where  otherwise noted, the files described below
       can be opened for reading only. In addition, if	a  process  becomes  a
       zombie  (one  that  has exited but whose	parent has not yet performed a
       wait(2) upon it), most of its associated	/proc files disappear from the
       hierarchy;  subsequent attempts to open them, or	to read	or write files
       opened before the process exited, will elicit the error ENOENT.

       Although	process	state and consequently the contents of /proc files can
       change  from  instant  to  instant, a single read(2) of a /proc file is
       guaranteed to return a sane representation of state; that is, the  read
       will  be	atomic with respect to the state of the	process. No such guar-
       antee applies to	successive reads applied to a /proc file for a running
       process.	 In  addition,	atomicity is not guaranteed for	I/O applied to
       the as (address-space) file for a running  process  or  for  a  process
       whose  address space contains memory shared by another running process.

       A number	of structure definitions are used to describe the files. These
       structures  may	grow  by the addition of elements at the end in	future
       releases	of the system and it is	not legitimate for a program to	assume
       that they will not.

STRUCTURE OF /proc/pid
       A  given	 directory /proc/pid contains the following entries. A process
       can use the invisible alias /proc/self if it wishes to open one of  its
       own /proc files (invisible in the sense that the	name ``self'' does not
       appear in a directory  listing  of  /proc  obtained  from  ls(1),  get-
       dents(2), or readdir(3C)).

   as
       Contains	 the  address-space image of the process; it can be opened for
       both reading and	writing. lseek(2) is used to position the file at  the
       virtual	address	of interest and	then the address space can be examined
       or changed through  read(2)  or	write(2)  (or  by  using  pread(2)  or
       pwrite(2) for the combined operation).

   ctl
       A  write-only  file  to which structured	messages are written directing
       the system to change some aspect	of the process's state or control  its
       behavior	 in  some way. The seek	offset is not relevant when writing to
       this file. Individual lwps also have associated lwpctl files in the lwp
       subdirectories.	A  control  message  may  be  written  either  to  the
       process's ctl file or to	a specific lwpctl file with operation-specific
       effects.	 The  effect  of a control message is immediately reflected in
       the state of the	process	visible	through	appropriate status and	infor-
       mation  files.  The  types  of control messages are described in	detail
       later. See CONTROL MESSAGES.

   status
       Contains	state information about	the  process  and  the	representative
       lwp.  The  file contains	a pstatus structure which contains an embedded
       lwpstatus structure for the representative lwp, as follows:

       typedef struct pstatus {
	  int pr_flags;		    /* flags (see below) */
	  int pr_nlwp;		    /* number of lwps in the process */
	  pid_tpr_pid;		    /* process id */
	  pid_tpr_ppid;		    /* parent process id */
	  pid_tpr_pgid;		    /* process group id	*/
	  pid_tpr_sid;		    /* session id */
	  id_t pr_aslwpid;	    /* obsolete	*/
	  id_t pr_agentid;	    /* lwp-id of the agent lwp,	if any */
	  sigset_t pr_sigpend;	    /* set of process pending signals */
	  uintptr_t pr_brkbase;	    /* virtual address of the process heap */
	  size_t pr_brksize;	    /* size of the process heap, in bytes */
	  uintptr_t pr_stkbase;	    /* virtual address of the process stack */
	  size_tpr_stksize;	    /* size of the process stack, in bytes */
	  timestruc_t pr_utime;	    /* process user cpu	time */
	  timestruc_t pr_stime;	    /* process system cpu time */
	  timestruc_t pr_cutime;    /* sum of children's user times */
	  timestruc_t r_cstime;	    /* sum of children's system	times */
	  sigset_t pr_sigtrace;	    /* set of traced signals */
	  fltset_t pr_flttrace;	    /* set of traced faults */
	  sysset_t pr_sysentry;	    /* set of system calls traced on entry */
	  sysset_t pr_sysexit;	    /* set of system calls traced on exit */
	  char pr_dmodel;	    /* data model of the process */
	  taskid_t pr_taskid;	    /* task id */
	  projid_t pr_projid;	    /* project id */
	  lwpstatus_t pr_lwp;	    /* status of the representative lwp	*/
       } pstatus_t;

       pr_flags	is a bit-mask holding the following process flags. For	conve-
       nience,	it  also  contains  the	 lwp flags for the representative lwp,
       described later.

       PR_ISSYS
	     process is	a system process (see PCSTOP).

       PR_VFORKP
	     process is	the parent of a	vforked	child (see PCWATCH).

       PR_FORK
	     process has its inherit-on-fork mode set (see PCSET).

       PR_RLC
	     process has its run-on-last-close mode set	(see PCSET).

       PR_KLC
	     process has its kill-on-last-close	mode set (see PCSET).

       PR_ASYNC
	     process has its asynchronous-stop mode set	(see PCSET).

       PR_MSACCT
	     process has microstate accounting enabled (see PCSET).

       PR_MSFORK
	     process microstate	accounting is inherited	on fork	(see PCSET).

       PR_BPTADJ
	     process has its breakpoint	adjustment mode	set (see PCSET).

       PR_PTRACE
	     process has its ptrace-compatibility mode set (see	PCSET).

       pr_nlwp is the total number of lwps in the process.

       pr_pid, pr_ppid,	pr_pgid, and pr_sid are, respectively, the process ID,
       the ID of the process's parent, the process's process group ID, and the
       process's session ID.

       pr_aslwpid is obsolete and is always zero.

       pr_agentid is the lwp-ID	for the	/proc agent lwp	(see the PCAGENT  con-
       trol operation).	It is zero if there is no agent	lwp in the process.

       pr_sigpend identifies asynchronous signals pending for the process.

       pr_brkbase is the virtual address of the	process	heap and pr_brksize is
       its size	in bytes. The address formed by	the sum	of these values	is the
       process	break  (see  brk(2)).  pr_stkbase  and pr_stksize are, respec-
       tively, the virtual address of the process stack	and its	size in	bytes.
       (Each  lwp  runs	on a separate stack; the distinguishing	characteristic
       of the process stack is that the	operating system  will	grow  it  when
       necessary.)

       pr_utime,  pr_stime,  pr_cutime,	 and  pr_cstime	are, respectively, the
       user CPU	and system CPU time consumed by	the process, and  the  cumula-
       tive  user  CPU and system CPU time consumed by the process's children,
       in seconds and nanoseconds.

       pr_sigtrace and pr_flttrace contain, respectively, the set  of  signals
       and  the	set of hardware	faults that are	being traced (see PCSTRACE and
       PCSFAULT).

       pr_sysentry and pr_sysexit contain, respectively, the  sets  of	system
       calls being traced on entry and exit (see PCSENTRY and PCSEXIT).

       pr_dmodel indicates the data model of the process. Possible values are:

       PR_MODEL_ILP32
	     process data model	is ILP32.

       PR_MODEL_LP64
	     process data model	is LP64.

       PR_MODEL_NATIVE
	     process data model	is native.

       The constant PR_MODEL_NATIVE reflects the data model of the controlling
       process,	 that is, its value is PR_MODEL_ILP32 or PR_MODEL_LP64 accord-
       ing to whether the controlling process has been compiled	 as  a	32-bit
       program or a 64-bit program, respectively.

       pr_lwp contains the status information for the representative lwp:

       typedef struct lwpstatus	{
	int pr_flags;		     /*	flags (see below) */
	id_t pr_lwpid;		     /*	specific lwp identifier	*/
	short pr_why;		     /*	reason for lwp stop, if	stopped	*/
	short pr_what;		     /*	more detailed reason */
	short pr_cursig;	     /*	current	signal,	if any */
	siginfo_t pr_info;	     /*	info associated	with signal or fault */
	sigset_t pr_lwppend;	     /*	set of signals pending to the lwp */
	sigset_t pr_lwphold;	     /*	set of signals blocked by the lwp */
	struct sigaction pr_action;  /*	signal action for current signal */
	stack_t	pr_altstack;	     /*	alternate signal stack info */
	uintptr_t pr_oldcontext;     /*	address	of previous ucontext */
	short pr_syscall;	     /*	system call number (if in syscall) */
	short pr_nsysarg;	     /*	number of arguments to this syscall */
	int pr_errno;		     /*	errno for failed syscall */
	long pr_sysarg[PRSYSARGS];   /*	arguments to this syscall */
	long pr_rval1;		     /*	primary	syscall	return value */
	long pr_rval2;		     /*	second syscall return value, if	any */
	char pr_clname[PRCLSZ];	     /*	scheduling class name */
	timestruc_t pr_tstamp;	     /*	real-time time stamp of	stop */
	ulong_t	pr_instr;	     /*	current	instruction */
	prgregset_t pr_reg;	     /*	general	registers */
	prfpregset_t pr_fpreg;	     /*	floating-point registers */
       } lwpstatus_t;

       pr_flags	 is  a	bit-mask  holding  the following lwp flags. For	conve-
       nience, it also contains	the process flags, described previously.

       PR_STOPPED
	     lwp is stopped.

       PR_ISTOP
	     lwp is stopped on an event	of interest (see PCSTOP).

       PR_DSTOP
	     lwp has a stop directive in effect	(see PCSTOP).

       PR_STEP
	     lwp has a single-step directive in	effect (see PCRUN).

       PR_ASLEEP
	     lwp is in an interruptible	sleep within a system call.

       PR_PCINVAL
	     lwp's current instruction (pr_instr) is undefined.

       PR_ASLWP
	     this flag is obsolete and is never	set..

       PR_AGENT
	     this is the /proc agent lwp for the process.

       pr_lwpid	names the specific lwp.

       pr_why and pr_what together describe, for a stopped lwp,	the reason for
       the stop. Possible values of pr_why and the associated pr_what are:

       PR_REQUESTED
	     indicates that the	stop occurred in response to a stop directive,
	     normally because  PCSTOP  was  applied  or	 because  another  lwp
	     stopped  on  an  event of interest	and the	asynchronous-stop flag
	     (see PCSET) was not set for the process.  pr_what	is  unused  in
	     this case.

       PR_SIGNALLED
	     indicates	that  the  lwp	stopped	 on  receipt  of a signal (see
	     PCSTRACE);	pr_what	holds the signal number	that caused  the  stop
	     (for a newly-stopped lwp, the same	value is in pr_cursig).

       PR_FAULTED
	     indicates that the	lwp stopped on incurring a hardware fault (see
	     PCSFAULT);	pr_what	holds the fault	number that caused the stop.

       PR_SYSENTRY

       PR_SYSEXIT
	     indicate a	stop on	entry to or  exit  from	 a  system  call  (see
	     PCSENTRY and PCSEXIT); pr_what holds the system call number.

       PR_JOBCONTROL
	     indicates that the	lwp stopped due	to the default action of a job
	     control stop signal (see sigaction(2)); pr_what holds  the	 stop-
	     ping signal number.

       PR_SUSPENDED
	     indicates that the	lwp stopped due	to internal synchronization of
	     lwps within the process. pr_what is unused	in this	case.

       pr_cursig names the current signal, that	is,  the  next	signal	to  be
       delivered  to  the  lwp,	 if any. pr_info, when the lwp is in a PR_SIG-
       NALLED or PR_FAULTED stop, contains additional information pertinent to
       the particular signal or	fault (see <sys/siginfo.h>).

       pr_lwppend  identifies  any synchronous or directed signals pending for
       the lwp.	pr_lwphold identifies those signals whose  delivery  is	 being
       blocked by the lwp (the signal mask).

       pr_action contains the signal action information	pertaining to the cur-
       rent signal (see	sigaction(2)); it is undefined if pr_cursig  is	 zero.
       pr_altstack contains the	alternate signal stack information for the lwp
       (see sigaltstack(2)).

       pr_oldcontext, if not zero, contains the	address	on the lwp stack of  a
       ucontext	 structure  describing	the  previous  user-level context (see
       ucontext(3HEAD)). It is non-zero	only if	the lwp	is  executing  in  the
       context of a signal handler.

       pr_syscall  is the number of the	system call, if	any, being executed by
       the lwp;	it is non-zero if and only if the lwp is stopped on  PR_SYSEN-
       TRY  or	PR_SYSEXIT,  or	 is asleep within a system call	( PR_ASLEEP is
       set). If	pr_syscall is non-zero,	pr_nsysarg is the number of  arguments
       to the system call and pr_sysarg	contains the actual arguments.

       pr_rval1, pr_rval2, and pr_errno	are defined only if the	lwp is stopped
       on PR_SYSEXIT or	if the PR_VFORKP flag is set.  If  pr_errno  is	 zero,
       pr_rval1	 and  pr_rval2 contain the return values from the system call.
       Otherwise, pr_errno contains the	error number for  the  failing	system
       call (see <sys/errno.h>).

       pr_clname contains the name of the lwp's	scheduling class.

       pr_tstamp,  if  the  lwp	is stopped, contains a time stamp marking when
       the lwp stopped,	in real	time seconds and nanoseconds  since  an	 arbi-
       trary time in the past.

       pr_instr	 contains  the	machine	instruction to which the lwp's program
       counter refers. The amount  of  data  retrieved	from  the  process  is
       machine-dependent.  On SPARC based machines, it is a 32-bit word. On IA
       based machines, it is a single byte. In general,	the size  is  that  of
       the  machine's  smallest	instruction. If	PR_PCINVAL is set, pr_instr is
       undefined; this occurs whenever the lwp is not stopped or when the pro-
       gram counter refers to an invalid virtual address.

       pr_reg is an array holding the contents of a stopped lwp's general reg-
       isters.

       SPARC On	SPARC-based machines, the predefined constants R_G0 ...	 R_G7,
	     R_O0 ... R_O7, R_L0 ... R_L7, R_I0	... R_I7, R_PC,	R_nPC, and R_Y
	     can be used as indices to refer to	the  corresponding  registers;
	     previous  register	 windows can be	read from their	overflow loca-
	     tions on the  stack  (however,  see  the  gwindows	 file  in  the
	     /proc/pid/lwp/lwpid subdirectory).

       SPARC V8	(32-bit)
	     For  SPARC	V8 (32-bit) controlling	processes, the predefined con-
	     stants R_PSR, R_WIM, and R_TBR can	be used	as indices to refer to
	     the  corresponding	special	registers.  For	SPARC V9 (64-bit) con-
	     trolling processes, the predefined	constants  R_CCR,  R_ASI,  and
	     R_FPRS  can be used as indices to refer to	the corresponding spe-
	     cial registers.

       IA    On	IA based machines, the predefined constants SS,	UESP, EFL, CS,
	     EIP, ERR, TRAPNO, EAX, ECX, EDX, EBX, ESP,	EBP, ESI, EDI, DS, ES,
	     FS, and GS	can be used as indices to refer	to  the	 corresponding
	     registers.

       pr_fpreg	is a structure holding the contents of the floating-point reg-
       isters.

       SPARC registers,	both general and floating-point, as seen by  a	64-bit
       controlling  process  are the V9	versions of the	registers, even	if the
       target process is a 32-bit (V8) process.	V8 registers are a  subset  of
       the V9 registers.

       If the lwp is not stopped, all register values are undefined.

   psinfo
       Contains	 miscellaneous information about the process and the represen-
       tative lwp needed by the	ps(1) command. psinfo is  accessible  after  a
       process	becomes	 a  zombie. The	file contains a	psinfo structure which
       contains	an embedded lwpsinfo structure for the representative lwp,  as
       follows:

       typedef struct psinfo {
	    int	pr_flag;	      /* process flags */
	    int	pr_nlwp;	      /* number	of lwps	in the process */
	    pid_t pr_pid;	      /* process id */
	    pid_t pr_ppid;	      /* process id of parent */
	    pid_t pr_pgid;	      /* process id of process group leader */
	    pid_t pr_sid;	      /* session id */
	    uid_t pr_uid;	      /* real user id */
	    uid_t pr_euid;	      /* effective user	id */
	    gid_t pr_gid;	      /* real group id */
	    gid_t pr_egid;	      /* effective group id */
	    uintptr_t pr_addr;	      /* address of process */
	    size_t pr_size;	      /* size of process image in Kbytes */
	    size_t pr_rssize;	      /* resident set size in Kbytes */
	    dev_t pr_ttydev;	      /* controlling tty device	(or PRNODEV) */
	    ushort_t pr_pctcpu;	      /* % of recent cpu time used by all lwps */
	    ushort_t pr_pctmem;	      /* % of system memory used by process */
	    timestruc_t	pr_start;     /* process start time, from the epoch */
	    timestruc_t	pr_time;      /* cpu time for this process */
	    timestruc_t	pr_ctime;     /* cpu time for reaped children */
	    taskid_t pr_taskid;	      /* task id */
	    projid_t pr_projid;	      /* project id */
	    char pr_fname[PRFNSZ];    /* name of exec'ed file */
	    char pr_psargs[PRARGSZ];  /* initial characters of arg list	*/
	    int	pr_wstat;	      /* if zombie, the	wait() status */
	    int	pr_argc;	      /* initial argument count	*/
	    uintptr_t pr_argv;	      /* address of initial argument vector */
	    uintptr_t pr_envp;	      /* address of initial environment	vector */
	    char pr_dmodel;	      /* data model of the process */
	    lwpsinfo_t pr_lwp;	      /* information for representative	lwp */
       } psinfo_t;

       Some  of	 the  entries in psinfo, such as pr_flag and pr_addr, refer to
       internal	kernel data structures and should not be  expected  to	retain
       their meanings across different versions	of the operating system.

       pr_pctcpu and pr_pctmem are 16-bit binary fractions in the range	0.0 to
       1.0 with	the binary point to the	right of the high-order	 bit  (1.0  ==
       0x8000).	pr_pctcpu is the summation over	all lwps in the	process.

       pr_lwp  contains	 the  ps(1) information	for the	representative lwp. If
       the process is a	zombie,	pr_nlwp	and pr_lwp.pr_lwpid are	zero  and  the
       other fields of pr_lwp are undefined:

       typedef struct lwpsinfo {
	    int	pr_flag;	      /* lwp flags */
	    id_t pr_lwpid;	      /* lwp id	*/
	    uintptr_t pr_addr;	      /* internal address of lwp */
	    uintptr_t pr_wchan;	      /* wait addr for sleeping	lwp */
	    char pr_stype;	      /* synchronization event type */
	    char pr_state;	      /* numeric lwp state */
	    char pr_sname;	      /* printable character for pr_state */
	    char pr_nice;	      /* nice for cpu usage */
	    short pr_syscall;	      /* system	call number (if	in syscall) */
	    char pr_oldpri;	      /* pre-SVR4, low value is	high priority */
	    char pr_cpu;	      /* pre-SVR4, cpu usage for scheduling */
	    int	pr_pri;		      /* priority, high	value =	high priority */
	    ushort_t pr_pctcpu;	      /* % of recent cpu time used by this lwp */
	    timestruc_t	pr_start;     /* lwp start time, from the epoch	*/
	    timestruc_t	pr_time;      /* cpu time for this lwp */
	    char pr_clname[PRCLSZ];   /* scheduling class name */
	    char pr_name[PRFNSZ];     /* name of system	lwp */
	    processorid_t pr_onpro;   /* processor which last ran this lwp */
	    processorid_t pr_bindpro; /* processor to which lwp	is bound */
	    psetid_t pr_bindpset;     /* processor set to which	lwp is bound */
       } lwpsinfo_t;

       Some  of	 the  entries in lwpsinfo, such	as pr_flag, pr_addr, pr_wchan,
       pr_stype, pr_state, and pr_name,	refer to internal kernel  data	struc-
       tures  and  should not be expected to retain their meanings across dif-
       ferent versions of the operating	system.

       pr_pctcpu is a 16-bit binary fraction, as described  above.  It	repre-
       sents  the  CPU	time  used  by	the specific lwp. On a multi-processor
       machine,	the maximum value is 1/N, where	N is the number	of CPUs.

   cred
       Contains	a description of the credentials associated with the process:

       typedef struct prcred {
	    uid_t pr_euid;	/* effective user id */
	    uid_t pr_ruid;	/* real	user id	*/
	    uid_t pr_suid;	/* saved user id (from exec) */
	    gid_t pr_egid;	/* effective group id */
	    gid_t pr_rgid;	/* real	group id */
	    gid_t pr_sgid;	/* saved group id (from	exec) */
	    int	pr_ngroups;	/* number of supplementary groups */
	    gid_t pr_groups[1];	/* array of supplementary groups */
       } prcred_t;

       The array of associated supplementary groups in pr_groups is  of	 vari-
       able  length;  the  cred	file contains all of the supplementary groups.
       pr_ngroups indicates the	number of supplementary	groups.	(See also  the
       PCSCRED control operation.)

   sigact
       Contains	an array of sigaction structures describing the	current	dispo-
       sitions of all signals associated with the traced process  (see	sigac-
       tion(2)).   Signal  numbers  are	 displaced by 1	from array indices, so
       that the	action for signal number n appears  in	position  n-1  of  the
       array.

   auxv
       Contains	 the initial values of the process's aux vector	in an array of
       auxv_t structures (see <sys/auxv.h>). The values	are  those  that  were
       passed  by  the	operating system as startup information	to the dynamic
       linker.

   ldt
       This file exists	only on	IA based machines. It is non-empty only	if the
       process	has  established a local descriptor table (LDT). If non-empty,
       the file	contains the array of currently	active LDT entries in an array
       of  elements of type struct ssd,	defined	in <sys/sysi86.h>, one element
       for each	active LDT entry.

   map
       Contains	information about the virtual address map of the process.  The
       file  contains  an array	of prmap structures, each of which describes a
       contiguous virtual address region in the	address	space  of  the	traced
       process:

       typedef struct prmap {
	    uintptr_tpr_vaddr;	       /* virtual address of mapping */
	    size_t pr_size;	       /* size of mapping in bytes */
	    char pr_mapname[PRMAPSZ];  /* name in /proc/pid/object */
	    offset_t pr_offset;	       /* offset into mapped object, if	any */
	    int	pr_mflags;	       /* protection and attribute flags */
	    int	pr_pagesize;	       /* pagesize for this mapping in bytes */
	    int	pr_shmid;	       /* SysV shared memory identifier	*/
       } prmap_t;

       pr_vaddr	 is  the  virtual  address  of	the  mapping within the	traced
       process and pr_size is its size in bytes. pr_mapname, if	 it  does  not
       contain a null string, contains the name	of a file in the object	direc-
       tory (see below)	that can be opened read-only to	obtain a file descrip-
       tor  for	 the  mapped  file associated with the mapping.	This enables a
       debugger	to find	object file symbol tables without having to  know  the
       real  path  names  of  the  executable file and shared libraries	of the
       process.	pr_offset is the 64-bit	offset within the mapped file (if any)
       to which	the virtual address is mapped.

       pr_mflags is a bit-mask of protection and attribute flags:

       MA_READ
	     mapping is	readable by the	traced process.

       MA_WRITE
	     mapping is	writable by the	traced process.

       MA_EXEC
	     mapping is	executable by the traced process.

       MA_SHARED
	     mapping changes are shared	by the mapped object.

       MA_ISM
	     mapping is	intimate shared	memory (shared MMU resources).

       A  contiguous  area  of	the  address  space having the same underlying
       mapped object may appear	as multiple  mappings  due  to	varying	 read,
       write,  and  execute  attributes. The underlying	mapped object does not
       change over the range of	a single mapping. An I/O operation to  a  map-
       ping  marked MA_SHARED fails if applied at a virtual address not	corre-
       sponding	to a valid page	in the underlying mapped object. A write to  a
       MA_SHARED  mapping  that	is not marked MA_WRITE fails. Reads and	writes
       to private mappings  always  succeed.  Reads  and  writes  to  unmapped
       addresses fail.

       pr_pagesize is the page size for	the mapping, currently always the sys-
       tem pagesize.

       pr_shmid	is the shared memory identifier, if any, for the mapping.  Its
       value  is  -1  if  the  mapping	is  not	 System	 V  shared memory. See
       shmget(2).

   rmap
       Contains	information about the reserved address ranges of the  process.
       The  file  contains  an array of	prmap structures, as defined above for
       the map file. Each structure describes  a  contiguous  virtual  address
       region  in  the address space of	the traced process that	is reserved by
       the system in the sense that an mmap(2) system call that	does not spec-
       ify MAP_FIXED will not use any part of it for the new mapping. Examples
       of such reservations  include  the  address  ranges  reserved  for  the
       process	stack  and  the	 individual  thread stacks of a	multi-threaded
       process.

   cwd
       A symbolic  link	 to  the  process's  current  working  directory  (see
       chdir(2)).  A  readlink(2)  of /proc/pid/cwd yields a null string. How-
       ever, it	can be opened, listed, and searched as a directory and can  be
       the target of chdir(2).

   root
       A  symbolic  link  to  the process's root directory. /proc/pid/root can
       differ from the system root directory if	the  process  or  one  of  its
       ancestors  executed  chroot(2) as super-user. It	has the	same semantics
       as /proc/pid/cwd.

   fd
       A directory containing references to the	open  files  of	 the  process.
       Each entry is a decimal number corresponding to an open file descriptor
       in the process.

       If an entry refers to a regular file, it	can be opened with normal file
       system  semantics  but,	to  ensure that	the controlling	process	cannot
       gain greater access than	the controlled process,	with  no  file	access
       modes  other  than its read/write open modes in the controlled process.
       If an entry refers to a directory, it appears as	a  symbolic  link  and
       can be accessed with the	same semantics as /proc/pid/cwd. An attempt to
       open any	other type of entry fails with EACCES.

   object
       A directory containing read-only	files with names corresponding to  the
       pr_mapname  entries  in the map and pagedata files. Opening such	a file
       yields a	file descriptor	for the	underlying mapped file associated with
       an address-space	mapping	in the process.	The file name a.out appears in
       the directory as	an alias for the process's executable file.

       The object directory makes it possible for  a  controlling  process  to
       gain  access  to	 the  object file and any shared libraries (and	conse-
       quently the symbol tables) without having to know the actual path names
       of the executable files.

   pagedata
       Opening the page	data file enables tracking of address space references
       and modifications on a per-page basis.

       A read(2) of the	page data file descriptor returns structured page data
       and atomically clears the page data maintained for the file by the sys-
       tem. That is to say, each read returns data collected  since  the  last
       read;  the first	read returns data collected since the file was opened.
       When the	call completes,	the read buffer	contains the following	struc-
       ture  as	 its header and	thereafter contains a number of	section	header
       structures and associated byte arrays that must be accessed by  walking
       linearly	through	the buffer.

       typedef struct prpageheader {
	    timestruc_t	pr_tstamp; /* real time	stamp, time of read() */
	    ulong_t pr_nmap;	   /* number of	address	space mappings */
	    ulong_t pr_npage;	   /* total number of pages */
       } prpageheader_t;

       The  header  is	followed  by pr_nmap prasmap structures	and associated
       data arrays. The	prasmap	structure contains the following elements:

       typedef struct prasmap {
	    uintptr_t pr_vaddr;	       /* virtual address of mapping */
	    ulong_t pr_npage;	       /* number of pages in mapping */
	    char pr_mapname[PRMAPSZ];  /* name in /proc/pid/object */
	    offset_t pr_offset;	       /* offset into mapped object, if	any */
	    int	pr_mflags;	       /* protection and attribute flags */
	    int	pr_pagesize;	       /* pagesize for this mapping in bytes */
	    int	pr_shmid;	       /* SysV shared memory identifier	*/
       } prasmap_t;

       Each section header is followed by pr_npage bytes, one  byte  for  each
       page  in	 the  mapping, plus 0-7	null bytes at the end so that the next
       prasmap structure begins	on an eight-byte aligned boundary.  Each  data
       byte may	contain	these flags:

       PG_REFERENCED
	     page has been referenced.

       PG_MODIFIED
	     page has been modified.

       If the read buffer is not large enough to contain all of	the page data,
       the read	fails with E2BIG  and  the  page  data	is  not	 cleared.  The
       required	 size  of  the read buffer can be determined through fstat(2).
       Application of lseek(2) to the page data	file  descriptor  is  ineffec-
       tive;  every  read  starts  from	the beginning of the file. Closing the
       page data file descriptor terminates  the  system  overhead  associated
       with collecting the data.

       More  than  one	page  data file	descriptor for the same	process	can be
       opened, up to a system-imposed limit per	traced process.	A read of  one
       does  not affect	the data being collected by the	system for the others.
       An open of the page data	file will fail	with  ENOMEM  if  the  system-
       imposed limit would be exceeded.

   watch
       Contains	 an  array  of	prwatch	 structures, one for each watched area
       established by the PCWATCH control operation. See PCWATCH for  details.

   usage
       Contains	 process  usage	 information  described	by a prusage structure
       which contains at least the following fields:

       typedef struct prusage {
	    id_tpr_lwpid;	     /*	lwp id.	 0: process or defunct */
	    int	pr_count;	     /*	number of contributing lwps */
	    timestruc_t	pr_tstamp;   /*	real time stamp, time of read()	*/
	    timestruc_t	pr_create;   /*	process/lwp creation time stamp	*/
	    timestruc_t	pr_term;     /*	process/lwp termination	time stamp */
	    timestruc_t	pr_rtime;    /*	total lwp real (elapsed) time */
	    timestruc_t	pr_utime;    /*	user level CPU time */
	    timestruc_t	pr_stime;    /*	system call CPU	time */
	    timestruc_t	pr_ttime;    /*	other system trap CPU time */
	    timestruc_t	pr_tftime;   /*	text page fault	sleep time */
	    timestruc_t	pr_dftime;   /*	data page fault	sleep time */
	    timestruc_t	pr_kftime;   /*	kernel page fault sleep	time */
	    timestruc_t	pr_ltime;    /*	user lock wait sleep time */
	    timestruc_t	pr_slptime;  /*	all other sleep	time */
	    timestruc_t	pr_wtime;    /*	wait-cpu (latency) time	*/
	    timestruc_t	pr_stoptime; /*	stopped	time */
	    ulong_t pr_minf;	     /*	minor page faults */
	    ulong_t pr_majf;	     /*	major page faults */
	    ulong_t pr_nswap;	     /*	swaps */
	    ulong_t pr_inblk;	     /*	input blocks */
	    ulong_t pr_oublk;	     /*	output blocks */
	    ulong_t pr_msnd;	     /*	messages sent */
	    ulong_t pr_mrcv;	     /*	messages received */
	    ulong_t pr_sigs;	     /*	signals	received */
	    ulong_t pr_vctx;	     /*	voluntary context switches */
	    ulong_t pr_ictx;	     /*	involuntary context switches */
	    ulong_t pr_sysc;	     /*	system calls */
	    ulong_t pr_ioch;	     /*	chars read and written */
       } prusage_t;

       If microstate accounting	has not	been enabled for the process (see  the
       PR_MSACCT flag for the PCSET operation, below), the usage file contains
       only an estimate	of times spent in the various states. The  usage  file
       is accessible after a process becomes a zombie.

   lstatus
       Contains	 a prheader structure followed by an array of lwpstatus	struc-
       tures,	one   for   each   lwp	  in	the    process	  (see	  also
       /proc/pid/lwp/lwpid/lwpstatus, below). The prheader structure describes
       the number and size of the array	entries	that follow.

       typedef struct prheader {
	    long pr_nent;	 /* number of entries */
	    size_t pr_entsize;	 /* size of each entry,	in bytes */
       } prheader_t;

       The lwpstatus structure may grow	by the addition	of elements at the end
       in  future  releases of the system. Programs must use pr_entsize	in the
       file header to index through the	array. These  comments	apply  to  all
       /proc  files  that  include  a  prheader	structure (lpsinfo and lusage,
       below).

   lpsinfo
       Contains	a prheader structure followed by an array of  lwpsinfo	struc-
       tures,	 one	for    each    lwp   in	  the	process.   (See	  also
       /proc/pid/lwp/lwpid/lwpsinfo, below.)

   lusage
       Contains	a prheader structure followed by an array  of  prusage	struc-
       tures,  one  for	 each lwp in the process plus an additional element at
       the beginning that contains the summation over all defunct  lwps	 (lwps
       that  once  existed  but	no longer exist	in the process). Excluding the
       pr_lwpid, pr_tstamp, pr_create, and pr_term entries, the	entry-by-entry
       summation  over	all  these structures is the definition	of the process
       usage  information  obtained   from   the   usage   file.   (See	  also
       /proc/pid/lwp/lwpid/lwpusage, below.)

   lwp
       A  directory  containing	 entries each of which names an	lwp within the
       process.	These entries are themselves directories containing additional
       files as	described below.

STRUCTURE OF /proc/pid/lwp/ lwpid
       A given directory /proc/pid/lwp/lwpid contains the following entries:

   lwpctl
       Write-only  control  file. The messages written to this file affect the
       specific	lwp rather than	the representative lwp,	as is the case for the
       process's ctl file.

   lwpstatus
       lwp-specific state information. This file contains the lwpstatus	struc-
       ture for	the specific lwp as described above for	the representative lwp
       in the process's	status file.

   lwpsinfo
       lwp-specific  ps(1) information.	This file contains the lwpsinfo	struc-
       ture for	the specific lwp as described above for	the representative lwp
       in the process's	psinfo file.

   lwpusage
       This  file  contains  the  prusage  structure  for  the specific	lwp as
       described above for the process's usage file.

   gwindows
       This file exists	only on	SPARC based machines. If it is	non-empty,  it
       contains	 a  gwindows_t	structure, defined in <sys/regset.h>, with the
       values of those SPARC register windows that could not be	stored on  the
       stack when the lwp stopped. Conditions under which register windows are
       not stored on the stack are: the	stack pointer  refers  to  nonexistent
       process	memory	or the stack pointer is	improperly aligned. If the lwp
       is not stopped or if there are no register windows that	could  not  be
       stored on the stack, the	file is	empty (the usual case).

   xregs
       Extra  state  registers.	 The  extra state register set is architecture
       dependent; this file is empty if	the  system  does  not	support	 extra
       state  registers. If the	file is	non-empty, it contains an architecture
       dependent structure of type prxregset_t,	defined	 in  <procfs.h>,  with
       the  values  of	the  lwp's  extra  state  registers. If	the lwp	is not
       stopped,	all register values are	undefined. See also the	 PCSXREG  con-
       trol operation, below.

   asrs
       This  file  exists  only	 for 64-bit SPARC V9 processes.	It contains an
       asrset_t	structure, defined in <sys/regset.h>, containing the values of
       the  lwp's  platform-dependent ancillary	state registers. If the	lwp is
       not stopped, all	register values	are undefined.	See also  the  PCSASRS
       control operation, below.

CONTROL	MESSAGES
       Process	state  changes	are  effected  through	messages  written to a
       process's ctl file or to	an individual lwp's lwpctl file.  All  control
       messages	 consist  of a long that names the specific operation followed
       by additional data containing the operand, if any.

       Multiple	control	messages may be	combined  in  a	 single	 write(2)  (or
       writev(2)) to a control file, but no partial writes are permitted. That
       is, each	control	message, operation code	plus operand, if any, must  be
       presented  in  its entirety to the write(2) and not in pieces over sev-
       eral system calls. If a control operation fails,	no  subsequent	opera-
       tions contained in the same write(2) are	attempted.

       Descriptions  of	 the  allowable	control	messages follow. In all	cases,
       writing a message to a control file for a process or lwp	that has  ter-
       minated elicits the error ENOENT.

   PCSTOP PCDSTOP PCWSTOP PCTWSTOP
       When  applied  to  the process control file, PCSTOP directs all lwps to
       stop and	waits for them to stop,	PCDSTOP	directs	all lwps to stop with-
       out  waiting for	them to	stop, and PCWSTOP simply waits for all lwps to
       stop. When applied to an	lwp control file, PCSTOP directs the  specific
       lwp  to	stop  and waits	until it has stopped, PCDSTOP directs the spe-
       cific lwp to stop without waiting for it	to stop,  and  PCWSTOP	simply
       waits  for  the	specific  lwp  to stop.	When applied to	an lwp control
       file, PCSTOP and	PCWSTOP	complete when the lwp stops  on	 an  event  of
       interest,  immediately  if  already  so	stopped;  when	applied	to the
       process control file, they complete when	every lwp has  stopped	either
       on an event of interest or on a PR_SUSPENDED stop.

       PCTWSTOP	 is  identical to PCWSTOP except that it enables the operation
       to time out, to avoid waiting forever for a process  or	lwp  that  may
       never stop on an	event of interest. PCTWSTOP takes a long operand spec-
       ifying a	number of milliseconds;	the wait will  terminate  successfully
       after  the  specified number of milliseconds even if the	process	or lwp
       has not stopped;	a timeout value	of zero	makes the operation  identical
       to PCWSTOP.

       An  ``event  of interest'' is either a PR_REQUESTED stop	or a stop that
       has been	specified in the process's tracing  flags  (set	 by  PCSTRACE,
       PCSFAULT,  PCSENTRY, and	PCSEXIT). PR_JOBCONTROL	and PR_SUSPENDED stops
       are specifically	not events of interest.	(An lwp	may stop twice due  to
       a  stop	signal,	first showing PR_SIGNALLED if the signal is traced and
       again showing PR_JOBCONTROL if the lwp is set running without  clearing
       the signal.) If PCSTOP or PCDSTOP is applied to an lwp that is stopped,
       but not on an event of interest,	the stop directive takes  effect  when
       the  lwp	is restarted by	the competing mechanism. At that time, the lwp
       enters a	PR_REQUESTED stop before executing any user-level code.

       A write of a control message that blocks	is interruptible by  a	signal
       so  that,  for example, an alarm(2) can be set to avoid waiting forever
       for a process or	lwp that may never stop	on an event  of	 interest.  If
       PCSTOP  is  interrupted,	 the lwp stop directives remain	in effect even
       though the write(2) returns an error. (Use of PCTWSTOP with a  non-zero
       timeout is recommended over PCWSTOP with	an alarm(2).)

       A  system  process  (indicated  by the PR_ISSYS flag) never executes at
       user level, has no user-level address space visible through /proc,  and
       cannot be stopped. Applying one of these	operations to a	system process
       or any of its lwps elicits the error EBUSY.

   PCRUN
       Make an lwp runnable again after	a stop.	This operation	takes  a  long
       operand containing zero or more of the following	flags:

       PRCSIG
	     clears the	current	signal,	if any (see PCCSIG).

       PRCFAULT
	      clears the current fault,	if any (see PCCFAULT).

       PRSTEP
	      directs the lwp to execute a single machine instruction. On com-
	     pletion of	the instruction, a trace trap occurs. If  FLTTRACE  is
	     being  traced,  the  lwp stops; otherwise,	it is sent SIGTRAP. If
	     SIGTRAP is	being traced and is not	blocked, the lwp  stops.  When
	     the  lwp stops on an event	of interest, the single-step directive
	     is	cancelled, even	if the stop occurs before the  instruction  is
	     executed.	This  operation	requires hardware and operating	system
	     support and may not be  implemented  on  all  processors.	It  is
	     implemented on SPARC and IA based machines.

       PRSABORT
	      is  meaningful  only  if	the lwp	is in a	PR_SYSENTRY stop or is
	     marked PR_ASLEEP; it instructs the	lwp to abort execution of  the
	     system call (see PCSENTRY and PCSEXIT).

       PRSTOP
	      directs the lwp to stop again as soon as possible	after resuming
	     execution (see PCDSTOP). In particular, if	the lwp	is stopped  on
	     PR_SIGNALLED or PR_FAULTED, the next stop will show PR_REQUESTED,
	     no	other stop will	have intervened, and the  lwp  will  not  have
	     executed any user-level code.

       When  applied  to  an  lwp  control  file, PCRUN	clears any outstanding
       directed-stop request and makes the specific lwp	runnable.  The	opera-
       tion fails with EBUSY if	the specific lwp is not	stopped	on an event of
       interest	or has not been	directed to stop or if the  agent  lwp	exists
       and this	is not the agent lwp (see PCAGENT).

       When  applied to	the process control file, a representative lwp is cho-
       sen for the operation as	described for /proc/pid/status.	The  operation
       fails  with  EBUSY if the representative	lwp is not stopped on an event
       of interest or has not been directed  to	 stop  or  if  the  agent  lwp
       exists.	If  PRSTEP  or PRSTOP was requested, the representative	lwp is
       made runnable and its outstanding  directed-stop	 request  is  cleared;
       otherwise all outstanding directed-stop requests	are cleared and, if it
       was stopped on an event of interest, the	representative lwp  is	marked
       PR_REQUESTED. If, as a consequence, all lwps are	in the PR_REQUESTED or
       PR_SUSPENDED  stop  state,  all	lwps  showing  PR_REQUESTED  are  made
       runnable.

   PCSTRACE
       Define a	set of signals to be traced in the process. The	receipt	of one
       of these	signals	by an lwp causes the lwp to stop. The set  of  signals
       is  defined using an operand sigset_t contained in the control message.
       Receipt of SIGKILL cannot be  traced;  if  specified,  it  is  silently
       ignored.

       If  a  signal  that is included in an lwp's held	signal set (the	signal
       mask) is	sent to	the lwp, the signal is not received and	does not cause
       a  stop until it	is removed from	the held signal	set, either by the lwp
       itself or by setting the	held signal set	with PCSHOLD.

   PCCSIG
       The current signal, if any, is cleared from the specific	or representa-
       tive lwp.

   PCSSIG
       The  current  signal and	its associated signal information for the spe-
       cific or	representative lwp are set according to	the  contents  of  the
       operand	siginfo	structure (see <sys/siginfo.h>). If the	specified sig-
       nal number is zero, the current signal is  cleared.  The	 semantics  of
       this  operation	are different from those of kill(2) in that the	signal
       is delivered to the lwp immediately after execution is resumed (even if
       it  is  being  blocked)	and  an	 additional PR_SIGNALLED stop does not
       intervene even if the signal is traced. Setting the current  signal  to
       SIGKILL terminates the process immediately.

   PCKILL
       If applied to the process control file, a signal	is sent	to the process
       with semantics identical	to those of kill(2). If	applied	to an lwp con-
       trol file, a directed signal is sent to the specific lwp. The signal is
       named in	a long operand contained in the	message. Sending SIGKILL  ter-
       minates the process immediately.

   PCUNKILL
       A  signal  is  deleted,	that is, it is removed from the	set of pending
       signals.	If applied to the process control file,	the signal is  deleted
       from  the process's pending signals. If applied to an lwp control file,
       the signal is deleted from the lwp's pending signals. The current  sig-
       nal  (if	 any)  is unaffected. The signal is named in a long operand in
       the control message. It is an  error  (EINVAL)  to  attempt  to	delete
       SIGKILL.

   PCSHOLD
       Set  the	 set  of  held	signals	for the	specific or representative lwp
       (signals	whose delivery will be blocked if sent to the lwp). The	set of
       signals	is specified with a sigset_t operand. SIGKILL and SIGSTOP can-
       not be held; if specified, they are silently ignored.

   PCSFAULT
       Define a	set of hardware	faults to be traced in the process. On	incur-
       ring  one of these faults, an lwp stops.	The set	is defined via the op-
       erand fltset_t structure. Fault names are defined in <sys/fault.h>  and
       include	the  following.	Some of	these may not occur on all processors;
       there may be processor-specific faults in addition to these.

       FLTILL
	     illegal instruction

       FLTPRIV
	     privileged	instruction

       FLTBPT
	     breakpoint	trap

       FLTTRACE
	     trace trap	(single-step)

       FLTWATCH
	     watchpoint	trap

       FLTACCESS
	     memory access fault (bus error)

       FLTBOUNDS
	     memory bounds violation

       FLTIOVF
	     integer overflow

       FLTIZDIV
	     integer zero divide

       FLTFPE
	     floating-point exception

       FLTSTACK
	     unrecoverable stack fault

       FLTPAGE
	     recoverable page fault

       When not	traced,	a fault	normally results in the	posting	of a signal to
       the lwp that incurred the fault.	If an lwp stops	on a fault, the	signal
       is posted to the	lwp when execution is  resumed	unless	the  fault  is
       cleared	by  PCCFAULT or	by the PRCFAULT	option of PCRUN. FLTPAGE is an
       exception; no signal is posted. The  pr_info  field  in	the  lwpstatus
       structure  identifies  the  signal to be	sent and contains machine-spe-
       cific information about the fault.

   PCCFAULT
       The current fault, if any, is cleared; the associated signal  will  not
       be sent to the specific or representative lwp.

   PCSENTRY PCSEXIT
       These  control  operations instruct the process's lwps to stop on entry
       to or exit from specified system	calls. The set of system calls	to  be
       traced is defined via an	operand	sysset_t structure.

       When  entry to a	system call is being traced, an	lwp stops after	having
       begun the call to the system but	before the system call arguments  have
       been  fetched  from  the	 lwp.  When  exit  from	a system call is being
       traced, an lwp stops on completion of the system	 call  just  prior  to
       checking	 for  signals  and returning to	user level. At this point, all
       return values have been stored into the lwp's registers.

       If an lwp is stopped on entry to	a system call  (PR_SYSENTRY)  or  when
       sleeping	 in an interruptible system call (PR_ASLEEP is set), it	may be
       instructed to go	 directly  to  system  call  exit  by  specifying  the
       PRSABORT	 flag  in a PCRUN control message. Unless exit from the	system
       call is being traced, the lwp returns to	user level showing EINTR.

   PCWATCH
       Set or clear a watched area in the controlled process  from  a  prwatch
       structure operand:

       typedef struct prwatch {
	    uintptr_t pr_vaddr;	 /* virtual address of watched area */
	    size_t pr_size;	 /* size of watched area in bytes */
	    int	pr_wflags;	 /* watch type flags */
       } prwatch_t;

       pr_vaddr	 specifies  the	 virtual  address  of  an area of memory to be
       watched in the controlled process. pr_size specifies the	 size  of  the
       area,  in  bytes.  pr_wflags  specifies the type	of memory access to be
       monitored as a bit-mask of the following	flags:

       WA_READ
	     read access

       WA_WRITE
	     write access

       WA_EXEC
	     execution access

       WA_TRAPAFTER
	     trap after	the instruction	completes

       If pr_wflags is non-empty, a watched area is established	for  the  vir-
       tual  address  range specified by pr_vaddr and pr_size. If pr_wflags is
       empty, any previously-established watched area starting at  the	speci-
       fied virtual address is cleared;	pr_size	is ignored.

       A  watchpoint  is  triggered  when an lwp in the	traced process makes a
       memory reference	that covers at least one byte of a  watched  area  and
       the memory reference is as specified in pr_wflags. When an lwp triggers
       a watchpoint, it	incurs a watchpoint trap. If FLTWATCH is being traced,
       the  lwp	 stops;	 otherwise, it is sent a SIGTRAP signal; if SIGTRAP is
       being traced and	is not blocked,	the lwp	stops.

       The watchpoint trap occurs  before  the	instruction  completes	unless
       WA_TRAPAFTER  was specified, in which case it occurs after the instruc-
       tion completes. If it occurs before completion, the memory is not modi-
       fied.  If  it  occurs  after completion,	the memory is modified (if the
       access is a write access).

       pr_info in the lwpstatus	structure contains  information	 pertinent  to
       the watchpoint trap. In particular, the si_addr field contains the vir-
       tual address of the memory reference that triggered the watchpoint, and
       the   si_code  field  contains  one  of	TRAP_RWATCH,  TRAP_WWATCH,  or
       TRAP_XWATCH, indicating read, write, or execute	access,	 respectively.
       The  si_trapafter  field	 is  zero unless WA_TRAPAFTER is in effect for
       this watched area; non-zero indicates that the current  instruction  is
       not  the	instruction that incurred the watchpoint trap. The si_pc field
       contains	the virtual address of the instruction that incurred the trap.

       A  watchpoint  trap may be triggered while executing a system call that
       makes reference to the traced process's memory. The lwp that is execut-
       ing  the	system call incurs the watchpoint trap while still in the sys-
       tem call. If it stops as	a result, the lwpstatus	structure contains the
       system  call  number and	its arguments. If the lwp does not stop, or if
       it is set running again without clearing	the signal or fault, the  sys-
       tem  call  fails	with EFAULT. If	WA_TRAPAFTER was specified, the	memory
       reference will have completed and the memory will  have	been  modified
       (if the access was a write access) when the watchpoint trap occurs.

       If  more	 than one of WA_READ, WA_WRITE,	and WA_EXEC is specified for a
       watched area, and a single instruction incurs  more  than  one  of  the
       specified  types, only one is reported when the watchpoint trap occurs.
       The precedence is WA_EXEC, WA_READ, WA_WRITE ( WA_EXEC and WA_READ take
       precedence  over	WA_WRITE), unless WA_TRAPAFTER was specified, in which
       case it is WA_WRITE, WA_READ,  WA_EXEC (	WA_WRITE takes precedence).

       PCWATCH fails with EINVAL if an attempt is made to specify  overlapping
       watched areas or	if pr_wflags contains flags other than those specified
       above. It fails with ENOMEM if an attempt is  made  to  establish  more
       watched areas than the system can support (the system can support thou-
       sands).

       The child of a vfork(2) borrows the  parent's  address  space.  When  a
       vfork(2)	is executed by a traced	process, all watched areas established
       for the parent are suspended until the child terminates or performs  an
       exec(2).	 Any  watched areas established	independently in the child are
       cancelled when the parent resumes  after	 the  child's  termination  or
       exec(2).	 PCWATCH  fails	 with  EBUSY  if  applied  to  the parent of a
       vfork(2)	before the child has terminated	or performed an	 exec(2).  The
       PR_VFORKP  flag	is  set	 in  the  pstatus  structure for such a	parent
       process.

       Certain accesses	of the traced process's	address	space by the operating
       system  are immune to watchpoints. The initial construction of a	signal
       stack frame when	a signal is delivered to an lwp	 will  not  trigger  a
       watchpoint  trap	 even  if  the	new  frame covers watched areas	of the
       stack. Once the signal handler is entered, watchpoint traps occur  nor-
       mally.  On SPARC	based machines,	register window	overflow and underflow
       will not	trigger	watchpoint traps, even if  the	register  window  save
       areas cover watched areas of the	stack.

       Watched	areas are not inherited	by child processes, even if the	traced
       process's inherit-on-fork mode, PR_FORK,	is set (see PCSET, below). All
       watched areas are cancelled when	the traced process performs a success-
       ful exec(2).

   PCSET PCUNSET
       PCSET sets one or more modes of operation for the traced	process. PCUN-
       SET  unsets  these modes. The modes to be set or	unset are specified by
       flags in	an operand long	in the control message:

       PR_FORK
	      (inherit-on-fork): When set, the process's tracing flags and its
	     inherit-on-fork  mode  are	 inherited  by the child of a fork(2),
	     fork1(2), or vfork(2). When unset,	child processes	start with all
	     tracing flags cleared.

       PR_RLC
	      (run-on-last-close):  When  set and the last writable /proc file
	     descriptor	referring to the traced	process	or any of its lwps  is
	     closed,  all of the process's tracing flags and watched areas are
	     cleared, any outstanding stop directives are canceled, and	if any
	     lwps  are	stopped	on events of interest, they are	set running as
	     though PCRUN had been applied to them. When unset,	the  process's
	     tracing flags and watched areas are retained and lwps are not set
	     running on	last close.

       PR_KLC
	      (kill-on-last-close): When set and the last writable /proc  file
	     descriptor	 referring to the traced process or any	of its lwps is
	     closed, the process is terminated with SIGKILL.

       PR_ASYNC
	      (asynchronous-stop): When	set, a stop on an event	of interest by
	     one  lwp  does  not directly affect any other lwp in the process.
	     When unset	and an lwp stops on an event of	 interest  other  than
	     PR_REQUESTED, all other lwps in the process are directed to stop.

       PR_MSACCT
	      (microstate accounting):	When  set,  microstate	accounting  is
	     enabled  for  the	process. This allows the usage file to contain
	     accurate values for the times the lwps  spent  in	their  various
	     processing	 states.  When	unset  (the  default), the overhead of
	     microstate	accounting is avoided and the usage file can only con-
	     tain an estimate of times spent in	the various states.

       PR_MSFORK
	      (inherit	 microstate  accounting):  When	 set,  and  microstate
	     accounting	is enabled for the process, microstate accounting will
	     be	 enabled  for  future  child processes.	When unset, child pro-
	     cesses start with microstate accounting disabled.

       PR_BPTADJ
	      (breakpoint trap pc adjustment): On IA based machines, a	break-
	     point  trap leaves	the program counter (the EIP) referring	to the
	     breakpointed instruction plus one byte.  When PR_BPTADJ  is  set,
	     the  system  will adjust the program counter back to the location
	     of	the breakpointed instruction when the lwp stops	 on  a	break-
	     point.  This  flag	 has  no effect	on SPARC based machines, where
	     breakpoint	traps leave  the  program  counter  referring  to  the
	     breakpointed instruction.

       PR_PTRACE
	      (ptrace-compatibility): When set,	a stop on an event of interest
	     by	the traced process is reported to the  parent  of  the	traced
	     process  via  wait(2), SIGTRAP is sent to the traced process when
	     it	executes a successful exec(2),	setuid/setgid  flags  are  not
	     honored for execs performed by the	traced process,	any exec of an
	     object file that the traced process cannot	read  fails,  and  the
	     process dies when its parent dies.	This mode is deprecated; it is
	     provided only to allow ptrace(2) to be implemented	as  a  library
	     function using /proc.

       It  is  an  error  (EINVAL) to specify flags other than those described
       above or	to apply these operations to a	system	process.  The  current
       modes  are  reported  in	 the  pr_flags	field  of /proc/pid/status and
       /proc/pid/lwp/lwp/lwpstatus.

   PCSREG
       Set the general	registers  for	the  specific  or  representative  lwp
       according to the	operand	prgregset_t structure.

       On  SPARC based systems,	only the condition-code	bits of	the processor-
       status register (R_PSR) of SPARC	V8 (32-bit) processes can be  modified
       by PCSREG. Other	privileged registers cannot be modified	at all.

       On  IA based systems, only certain bits of the flags register (EFL) can
       be modified by PCSREG: these include the	 condition  codes,  direction-
       bit, and	overflow-bit.

       PCSREG fails with EBUSY if the lwp is not stopped on an event of	inter-
       est.

   PCSVADDR
       Set the address at which	execution will resume for the specific or rep-
       resentative lwp from the	operand	long. On SPARC based systems, both %pc
       and %npc	are set, with %npc set to the instruction following  the  vir-
       tual  address.  On  IA  based systems, only %eip	is set.	PCSVADDR fails
       with EBUSY if the lwp is	not stopped on an event	of interest.

   PCSFPREG
       Set the floating-point registers	for the	specific or representative lwp
       according  to the operand prfpregset_t structure.  An error (EINVAL) is
       returned	if the system does not support floating-point  operations  (no
       floating-point  hardware	and the	system does not	emulate	floating-point
       machine instructions). PCSFPREG fails with EBUSY	 if  the  lwp  is  not
       stopped on an event of interest.

   PCSXREG
       Set  the	 extra	state registers	for the	specific or representative lwp
       according to the	architecture-dependent operand prxregset_t  structure.
       An  error  (EINVAL)  is	returned  if the system	does not support extra
       state registers.	PCSXREG	fails with EBUSY if the	lwp is not stopped  on
       an event	of interest.

   PCSASRS
       Set  the	 ancillary  state registers for	the specific or	representative
       lwp according to	 the  SPARC  V9	 platform-dependent  operand  asrset_t
       structure.  An  error (EINVAL) is returned if either the	target process
       or the controlling process is not a 64-bit SPARC	V9  process.  Most  of
       the  ancillary  state registers are privileged registers	that cannot be
       modified. Only those that can be	 modified  are	set;  all  others  are
       silently	ignored. PCSASRS fails with EBUSY if the lwp is	not stopped on
       an event	of interest.

   PCAGENT
       Create an agent lwp in the controlled process with register values from
       the operand prgregset_t structure (see PCSREG, above). The agent	lwp is
       created in the stopped state showing PR_REQUESTED  and  with  its  held
       signal  set  (the  signal  mask)	 having	all signals except SIGKILL and
       SIGSTOP blocked.

       The PCAGENT operation fails with	EBUSY  unless  the  process  is	 fully
       stopped	via  /proc, that is, unless all	of the lwps in the process are
       stopped either on events	of interest or on PR_SUSPENDED,	or are stopped
       on  PR_JOBCONTROL and have been directed	to stop	via PCDSTOP.  It fails
       with EBUSY if an	agent lwp already exists. It fails with	ENOMEM if sys-
       tem resources for creating new lwps have	been exhausted.

       Any  PCRUN operation applied to the process control file	or to the con-
       trol file of an lwp other than the agent	lwp fails with EBUSY  as  long
       as  the	agent lwp exists. The agent lwp	must be	caused to terminate by
       executing the _lwp_exit(2)  system  call	 before	 the  process  can  be
       restarted.

       Once  the  agent	lwp is created,	its lwp-ID can be found	by reading the
       process status file. To facilitate opening the agent lwp's control  and
       status  files,  the directory name /propc/pid/lwp/agent is accepted for
       lookup operations as an invisible alias for /proc/pid/lwp/lwpid,	 lwpid
       being the lwp-ID	of the agent lwp (invisible in the sense that the name
       ``agent'' does not appear  in  a	 directory  listing  of	 /proc/pid/lwp
       obtained	from ls(1), getdents(2), or readdir(3C)).

       The purpose of the agent	lwp is to perform operations in	the controlled
       process on behalf of the	controlling process: to	gather information not
       directly	 available  via	/proc files, or	in general to make the process
       change state in ways not	directly available via	/proc  control	opera-
       tions.  To  make	 use  of an agent lwp, the controlling process must be
       capable	of  making  it	execute	 system	  calls	  (specifically,   the
       _lwp_exit(2)  system  call). The	register values	given to the agent lwp
       on creation are typically the registers of the representative  lwp,  so
       that the	agent lwp can use its stack.

       The  agent  lwp is not allowed to execute any variation of the fork(2),
       exec(2),	or _lwp_create(2) system calls.	Attempts to do so yield	 ENOT-
       SUP to the agent	lwp.

   PCREAD PCWRITE
       Read  or	 write the target process's address space via a	priovec	struc-
       ture operand:

       typedef struct priovec {
	    void *pio_base;	 /* buffer in controlling process */
	    size_t pio_len;	 /* size of read/write request in bytes	*/
	    off_t pio_offset;	 /* virtual address in target process */
       } priovec_t;

       These operations	have  the  same	 effect	 as  pread(2)  and  pwrite(2),
       respectively,  of  the target process's address space file. The differ-
       ence is that more than one PCREAD or PCWRITE control operation  can  be
       written	to the control file at once, and they can be interspersed with
       other control operations	in a single write to the control file. This is
       useful,	for example, when planting many	breakpoint instructions	in the
       process's address space,	or when	stepping over a	breakpointed  instruc-
       tion.  Unlike  pread(2) and pwrite(2), no provision is made for partial
       reads or	writes;	if the operation cannot	be  performed  completely,  it
       fails with EIO.

   PCNICE
       The  traced process's nice(2) value is incremented by the amount	in the
       operand long. Only the super-user may better a  process's  priority  in
       this  way,  but	any user may lower the priority. This operation	is not
       meaningful for all scheduling classes.

   PCSCRED
       Set the target process credentials  to  the  values  contained  in  the
       prcred_t	 structure  operand (see /proc/pid/cred). The effective, real,
       and saved user-IDs and group-IDs	of the target  process	are  set.  The
       target  process's  supplementary	groups are not changed;	the pr_ngroups
       and pr_groups members of	the structure operand are  ignored.  Only  the
       super-user  may	perform	 this  operation; for all others it fails with
       EPERM.

PROGRAMMING NOTES
       For security reasons, except for	the psinfo,  usage,  lpsinfo,  lusage,
       lwpsinfo,  and lwpusage files, which are	world-readable,	and except for
       the super-user, an open of a /proc file fails unless both  the  user-ID
       and  group-ID  of  the caller match those of the	traced process and the
       process's object	file is	readable by the	caller.	Except for the	world-
       readable	files just mentioned, files corresponding to setuid and	setgid
       processes can be	opened only by the super-user.

       Even if held by the super-user, an open process or lwp file  descriptor
       (other  than  file  descriptors	for  the world-readable	files) becomes
       invalid if the traced process performs an exec(2)  of  a	 setuid/setgid
       object  file or an object file that the traced process cannot read. Any
       operation performed on an invalid  file	descriptor,  except  close(2),
       fails  with EAGAIN. In this situation, if any tracing flags are set and
       the process or any lwp file descriptor is open for writing, the process
       will  have  been	 directed  to stop and its run-on-last-close flag will
       have been set (see PCSET). This enables a controlling  process  (if  it
       has  permission)	 to  reopen  the  /proc	 files	to  get	new valid file
       descriptors, close the invalid file descriptors,	unset the run-on-last-
       close  flag  (if	 desired),  and	proceed. Just closing the invalid file
       descriptors causes the traced process  to  resume  execution  with  all
       tracing	flags  cleared.	Any process not	currently open for writing via
       /proc, but that has left-over tracing flags from	a previous  open,  and
       that  executes  a  setuid/setgid	or unreadable object file, will	not be
       stopped but will	have all its tracing flags cleared.

       To wait for one or more of a set	of processes or	lwps to	stop or	termi-
       nate,  /proc file descriptors (other than those obtained	by opening the
       cwd or root directories or by opening files in the fd or	object	direc-
       tories)	can  be	 used  in  a  poll(2)  system call. When requested and
       returned, either	of the polling events POLLPRI or POLLWRNORM  indicates
       that  the process or lwp	stopped	on an event of interest. Although they
       cannot be requested, the	polling	events POLLHUP,	POLLERR, and  POLLNVAL
       may  be	returned. POLLHUP indicates that the process or	lwp has	termi-
       nated. POLLERR indicates	that the file descriptor has  become  invalid.
       POLLNVAL	 is returned immediately if POLLPRI or POLLWRNORM is requested
       on a file descriptor referring to a system process  (see	 PCSTOP).  The
       requested events	may be empty to	wait simply for	termination.

FILES
       /proc directory (list of	processes)

       /proc/pid
	     specific process directory

       /proc/self
	     alias for a process's own directory

       /proc/pid/as
	     address space file

       /proc/pid/ctl
	     process control file

       /proc/pid/status
	     process status

       /proc/pid/lstatus
	     array of lwp status structs

       /proc/pid/psinfo
	     process ps(1) info

       /proc/pid/lpsinfo
	     array of lwp ps(1)	info structs

       /proc/pid/map
	     address space map

       /proc/pid/rmap
	     reserved address map

       /proc/pid/cred
	     process credentials

       /proc/pid/sigact
	     process signal actions

       /proc/pid/auxv
	     process aux vector

       /proc/pid/ldt
	     process LDT (IA only)

       /proc/pid/usage
	     process usage

       /proc/pid/lusage
	     array of lwp usage	structs

       /proc/pid/pagedata
	     process page data

       /proc/pid/watch
	     active watchpoints

       /proc/pid/cwd
	     symlink to	the current working directory

       /proc/pid/root
	     symlink to	the root directory

       /proc/pid/fd
	     directory (list of	open files)

       /proc/pid/fd/*
	     aliases for process's open	files

       /proc/pid/object
	     directory (list of	mapped files)

       /proc/pid/object/a.out
	     alias for process's executable file

       /proc/pid/object/*
	     aliases for other mapped files

       /proc/pid/lwp
	     directory (list of	lwps)

       /proc/pid/lwp/lwpid
	     specific lwp directory

       /proc/pid/lwp/agent
	     alias for the agent lwp directory

       /proc/pid/lwp/lwpid/lwpctl
	     lwp control file

       /proc/pid/lwp/lwpid/lwpstatus
	     lwp status

       /proc/pid/lwp/lwpid/lwpsinfo
	     lwp ps(1) info

       /proc/pid/lwp/lwpid/lwpusage
	     lwp usage

       /proc/pid/lwp/lwpid/gwindows
	     register windows (SPARC only)

       /proc/pid/lwp/lwpid/xregs
	     extra state registers

       /proc/pid/lwp/lwpid/asrs
	     ancillary state registers (SPARC V9 only)

SEE ALSO
       ls(1),	ps(1),	chroot(1M),  _lwp_create(2),  _lwp_exit(2),  alarm(2),
       brk(2),	chdir(2),  chroot(2),  close(2),  creat(2),  dup(2),  exec(2),
       fcntl(2),  fork(2), fork1(2), fstat(2), getdents(2), kill(2), lseek(2),
       mmap(2),	nice(2), open(2),  poll(2),  pread(2),	ptrace(2),  pwrite(2),
       read(2),	  readlink(2),	 readv(2),  shmget(2),	sigaction(2),  sigalt-
       stack(2), vfork(2), wait(2),  write(2),	writev(2),  readdir(3C),  sig-
       info(3HEAD),  signal(3HEAD),  types32(3HEAD),  ucontext(3HEAD),	lfcom-
       pile(5)

DIAGNOSTICS
       Errors that can occur in	addition to  the  errors  normally  associated
       with file system	access:

       ENOENT
	     The traced	process	or lwp has terminated after being opened.

       EIO   A	write(2)  was  attempted  at  an illegal address in the	traced
	     process.

       EBUSY PCSTOP, PCDSTOP, PCWSTOP, or PCTWSTOP was	applied	 to  a	system
	     process; an exclusive open(2) was attempted on a /proc file for a
	     process already open for writing; PCRUN, PCSREG, PCSVADDR,	 PCSF-
	     PREG,  or	PCSXREG	was applied to a process or lwp	not stopped on
	     an	event of interest; an attempt was made to mount	/proc when  it
	     was  already  mounted;  PCAGENT was applied to a process that was
	     not fully stopped or that already had an agent lwp.

       EPERM Someone other than	the super-user issued the  PCSCRED  operation;
	     someone other than	the super-user attempted to better a process's
	     priority by applying PCNICE.

       ENOSYS
	     An	attempt	was made to perform an unsupported operation (such  as
	     creat(2), link(2),	or unlink(2)) on an entry in /proc.

       EINVAL
	     In	general, this means that some invalid argument was supplied to
	     a system call. A non-exhaustive list of conditions	eliciting this
	     error includes: a control message operation code is undefined; an
	     out-of-range signal number	was specified with PCSSIG, PCKILL,  or
	     PCUNKILL;	SIGKILL	 was  specified	 with  PCUNKILL;  PCSFPREG was
	     applied on	a system that does not support	floating-point	opera-
	     tions;  PCSXREG  was  applied  on	a system that does not support
	     extra state registers.

       ENOMEM
	     The system-imposed	limit on the number of page data file descrip-
	     tors was reached on an open of /proc/pid/pagedata;	an attempt was
	     made with PCWATCH to establish more watched areas than the	system
	     can support; the PCAGENT operation	was issued when	the system was
	     out of resources for creating lwps.

       E2BIG Data to be	returned in a read(2) of the page  data	 file  exceeds
	     the size of the read buffer provided by the caller.

       EINTR A	signal	was  received by the controlling process while waiting
	     for the traced process or lwp to stop  via	 PCSTOP,  PCWSTOP,  or
	     PCTWSTOP.

       EAGAIN
	     The  traced  process  has performed an exec(2) of a setuid/setgid
	     object file or of an object file that it cannot read; all further
	     operations	  on  the  process  or	lwp  file  descriptor  (except
	     close(2)) elicit this error.

       EOVERFLOW
	     A 32-bit controlling process attempted to read or	write  the  as
	     file  or  attempted  to read the map, rmap, or pagedata file of a
	     64-bit target process. A 32-bit controlling process attempted  to
	     apply  one	 of  the control operations PCSREG, PCSXREG, PCSVADDR,
	     PCWATCH, PCAGENT, PCREAD, PCWRITE to a 64-bit target process.

NOTES
       Descriptions of structures in this document  include  only  interesting
       structure  elements,  not  filler and padding fields, and may show ele-
       ments out of order for descriptive clarity. The actual structure	 defi-
       nitions are contained in	<procfs.h>.

BUGS
       Because	the old	ioctl(2)-based version of /proc	is currently supported
       for binary compatibility	with old applications, the top-level directory
       for  a  process,	 /proc/pid,  is	 not  world-readable, but it is	world-
       searchable. Thus, anyone	can open /proc/pid/psinfo  even	 though	 ls(1)
       applied	to  /proc/pid will fail	for anyone but the owner or the	super-
       user. Support for the old  ioctl(2)-based  version  of  /proc  will  be
       dropped	in a future release, at	which time the top-level directory for
       a process will be made world-readable.

       On SPARC	based machines,	the types gregset_t and	fpregset_t defined  in
       <sys/regset.h> are similar to but not the same as the types prgregset_t
       and prfpregset_t	defined	in <procfs.h>.

SunOS 5.9			  23 Jul 2001			       proc(4)

NAME | DESCRIPTION | DIRECTORY STRUCTURE | CONTROL MESSAGES | PROGRAMMING NOTES | FILES | SEE ALSO | DIAGNOSTICS | NOTES | BUGS

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