PROG(3)                                                   PROG(3)

          prog - running programs

          bind #p /prog


          The prog device serves a two-level directory structure.  The
          first level contains numbered directories corresponding to
          pids of live Limbo processes; each such directory contains a
          set of files representing the corresponding process.  All
          files operate on UTF (see utf(6)) strings.

          The read-only status file contains seven space-separated
          fields.  The fields are: the process and process group iden-
          tifiers, each 8 characters right justified; the user name,
          at least 10 characters left justified; cpu time in minutes,
          seconds and tenths of seconds; the process state, 10 charac-
          ters left justified; the amount of memory used by the pro-
          cess in units of 1024 bytes, at least 5 characters, right
          justified, followed by a K; and the name of the current pro-
          gram module, up to 28 characters, left justified.

          The read-only pgrp file contains the process group identi-
          fier, in decimal.

          The read-only nsgrp file contains the namespace group iden-
          tifier, in decimal.

          The read-only ns file contains a set of mount and bind com-
          mands which describe the sys-bind(2) and mount operations
          used to construct the name space, in the format of
          namespace(6). The last line of the file is a cd command
          indicating the working directory.

          The read-only wait file may be read to recover information

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     PROG(3)                                                   PROG(3)

          about the exiting children of the process.  A read of wait
          will block until a child of the process, created after wait
          was opened, exits.  When such a child exits, it produces a
          string with three fields: the pid of the exiting process, a
          space, module name enclosed in  "'s, a colon, and a possibly
          empty error message.  The error message will contain at most
          64 characters.

          The read-only fd file describes the open file descriptors in
          the file descriptor group of the process.  Each line
          describes an open file.  The fields are: the file descriptor
          index, the open mode (r, w, rw); the type and number of the
          device; the path, version and type of the file's qid (see
          intro(5)); the file's atomic I/O unit, as defined in sys-
          iounit(2)); the file I/O offset in bytes; and the name with
          which it was opened.

          The read-only exception file gives details of the last
          exception to occur in the process, if any. The fields are
          the program counter value when the exception occurred, the
          module it occurred in and the exception itself, each sepa-
          rated by a space. If none, the result is the empty string.

          Messages written to the ctl file control the execution of
          the process.

          kill     Kill the process.

          killgrp  Kill all processes in the same group as the pro-
                   cess.  A process writing to its own ctl file does
                   not kill itself.

          exceptions propagate
                   Applies to process group leaders only (ie any pro-
                   cess that executes a system call sys->pctl(Sys-
                   >NEWPGRP, ... ).  If any process in the same group
                   as the leader incurs an exception which it does not
                   handle, atomically raise the exception in all pro-
                   cesses in the group.  In this case exceptions are
                   generated for killed processes as well. This mecha-
                   nism allows all processes in a process group to
                   perfom error recovery when one of them faults.

          exceptions notifyleader
                   Applies to process group leaders only.  If any pro-
                   cess in the same group as the leader incurs an
                   exception which it does not handle, atomically
                   destroy all processes in the group except for the
                   leader and raise the exception in the leader. This
                   error recovery mechanism might be appropriate when
                   a fault occurs amongst a group of processes and the

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     PROG(3)                                                   PROG(3)

                   group leader takes sole responsibilty for recovery.

                   Mark all processes that the process spawns in
                   future as restricted. A restricted process is one
                   which can run out of memory when a configured limit
                   has been reached and before total memory is
                   exhausted. An unrestricted process can allocate
                   memory until memory is truly exhausted. Typically a
                   window manager or server might be unrestricted as
                   they are processes fundamental to the running of a

          The dbgctl file provides facilities for debugging a process.
          Messages written to the file control the execution of the

          step n    Step the interpreter for at most n instructions,
                    or until a breakpoint is reached.

          toret     Step the interpreter until a return from the cur-
                    rent activation frame or a breakpoint is reached.

          cont      Step the interpreter until a breakpoint is

          stop      Stop the process as soon as possible.  Do not
                    allow the process to execute again until an unstop
                    message is received.

          unstop    Cancel the effect of any previous stop.

          bpt set path pc
                    Set a breakpoint at pc for the module given by

          bpt del path pc
                    Clear a breakpoint if one exists.

          Reading dbgctl gives updates for some state transitions
          while the process is being debugged.  Each update is termi-
          nated by a newline.

          exited    The process exited without error.

          broken: error
                    The process died due to error, a string with up to
                    64 characters.

          send      The process is blocked sending on a channel.

          recv      The process is blocked receiving on a channel.

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     PROG(3)                                                   PROG(3)

          alt       The process is blocked in an alt statement.

          run       The process is unblocked and now ready to run.

          new pid   The process has spawned a new process identified
                    by pid.

          The read-only stack file contains the dynamic call stack
          trace.  Each activation frame is described by one line with
          six fields, separated by a space: the frame pointer, program
          counter, module data pointer, and module code pointer, each
          8 hexadecimal digits; the execution method for the module (0
          means interpreted, 1 compiled); and the path name of the
          module.  The top activation frame starts at offset 0.

          The heap file may be queried to examine the state of the
          process.  A data query contains an address, a period, a for-
          mat character, and a count.  An instruction query contains a
          pc, a plus, a mode address, a period, the format I, and a
          count.  The addresses in the query may be decimal, hexadeci-
          mal preceded by 0x or 0X, or octal preceded by 0.  Count
          gives the number of consecutive data items retrieved by
          reading heap starting at offset 0; the format varies accord-
          ing to the format character.  All data items other than
          strings are terminated by a newline.

          W         32-bit decimal ints.

          B         8-bit unsigned decimal bytes.

          V         64-bit decimal bytes.

          R         64-bit reals.

          I         Disassembled Dis instructions.

          P         32-bit hexadecimal address, or nil.

          The following formats examine properties of specific 32-bit

          L         Examine a list, yielding a pair of hexadecimal
                    addresses separated by a period, giving the
                    address of the head and tail of a list.  It is an
                    error to use L on nil.

          A         Examine an array, yielding a decimal length, a
                    period, and the address of the 0th element of an
                    array, or nil.

          C         Examine a string, yielding the decimal length in
                    characters, a period, and the utf(6)

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     PROG(3)                                                   PROG(3)

                    representation of the string.

          M         Examine a module reference, yielding the address
                    of its global data or nil.

          The text file is currently unimplemented.


     Page 5                       Plan 9             (printed 10/2/22)