279 lines
6.7 KiB
Groff
279 lines
6.7 KiB
Groff
.\" $FreeBSD$
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.\" Written by Garrett Wollman
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.\" This file is in the public domain.
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.\"
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.Dd April 22, 2013
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.Dt PROCFS 5
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.Os
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.Sh NAME
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.Nm procfs
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.Nd process file system
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.Sh SYNOPSIS
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.Bd -literal
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proc /proc procfs rw 0 0
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.Ed
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.Sh DESCRIPTION
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The process file system, or
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.Nm ,
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implements a view of the system process table inside the file system.
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It is normally mounted on
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.Pa /proc ,
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and is required for the complete operation of programs such as
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.Xr ps 1
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and
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.Xr w 1 .
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.Pp
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The
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.Nm
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provides a two-level view of process space, unlike the previous
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.Fx 1.1
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.Nm
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implementation.
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At the highest level, processes themselves are named, according to
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their process ids in decimal, with no leading zeros.
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There is also a
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special node called
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.Pa curproc
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which always refers to the process making the lookup request.
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.Pp
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Each node is a directory which contains the following entries:
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.Pp
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Each directory contains several files:
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.Bl -tag -width status
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.It Pa ctl
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a write-only file which supports a variety
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of control operations.
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Control commands are written as strings to the
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.Pa ctl
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file.
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The control commands are:
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.Bl -tag -width detach -compact
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.It attach
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stops the target process and arranges for the sending
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process to become the debug control process.
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.It detach
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continue execution of the target process and
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remove it from control by the debug process (which
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need not be the sending process).
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.It run
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continue running the target process until
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a signal is delivered, a breakpoint is hit, or the
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target process exits.
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.It step
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single step the target process, with no signal delivery.
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.It wait
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wait for the target process to come to a steady
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state ready for debugging.
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The target process must be in this state before
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any of the other commands are allowed.
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.El
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.Pp
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The string can also be the name of a signal, lower case
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and without the
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.Dv SIG
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prefix,
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in which case that signal is delivered to the process
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(see
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.Xr sigaction 2 ) .
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.Pp
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The
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.Xr procctl 8
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utility can be used to clear tracepoints in a stuck process.
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.It Pa dbregs
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The debug registers as defined by
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.Dv "struct dbregs"
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in
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.In machine/reg.h .
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.Pa dbregs
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is currently only implemented on the i386 architecture.
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.It Pa etype
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The type of the executable referenced by the
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.Pa file
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entry.
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.It Pa file
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A symbolic link to the file from which the process text was read.
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This can be used to gain access to the process' symbol table,
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or to start another copy of the process.
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If the file cannot be found, the link target is
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.Ql unknown .
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.It Pa fpregs
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The floating point registers as defined by
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.Dv "struct fpregs"
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in
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.In machine/reg.h .
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.Pa fpregs
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is only implemented on machines which have distinct general
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purpose and floating point register sets.
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.It Pa map
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A map of the process' virtual memory.
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.It Pa mem
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The complete virtual memory image of the process.
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Only those address which exist in the process can be accessed.
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Reads and writes to this file modify the process.
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Writes to the text segment remain private to the process.
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.It Pa note
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Used for sending signals to the process.
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Not implemented.
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.It Pa notepg
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Used for sending signal to the process group.
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Not implemented.
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.It Pa osrel
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Allows read and write of the kernel osrel value assigned to the process.
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It affects the compatibility shims that are turned on and off
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depending on the value.
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Initial process value is read from the ABI note tag in the executed ELF image,
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and is zero if the tag not supported by binary format or was not found.
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.It Pa regs
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Allows read and write access to the process' register set.
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This file contains a binary data structure
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.Dv "struct regs"
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defined in
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.In machine/reg.h .
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.Pa regs
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can only be written when the process is stopped.
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.It Pa rlimit
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This is a read-only file containing the process current and maximum
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limits.
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Each line is of the format
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.Ar rlimit current max ,
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with -1
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indicating infinity.
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.It Pa status
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The process status.
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This file is read-only and returns a single line containing
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multiple space-separated fields as follows:
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.Pp
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.Bl -bullet -compact
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.It
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command name
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.It
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process id
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.It
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parent process id
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.It
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process group id
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.It
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session id
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.It
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device name
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of the controlling terminal, or
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a minus sign
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.Pq Dq -
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if there is no controlling terminal.
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.It
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a list of process flags:
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.Dv ctty
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if there is a controlling terminal,
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.Dv sldr
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if the process is a session leader,
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.Dv noflags
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if neither of the other two flags are set.
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.It
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the process start time in seconds and microseconds,
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comma separated.
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.It
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the user time in seconds and microseconds,
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comma separated.
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.It
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the system time in seconds and microseconds,
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comma separated.
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.It
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the wait channel message
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.It
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the process credentials consisting of
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the effective user id
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and the list of groups (whose first member
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is the effective group id)
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all comma separated.
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.It
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the hostname of the jail in which the process runs, or
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.Ql -
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to indicate that the process is not running within a jail.
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.El
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.El
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.Pp
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In a normal debugging environment,
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where the target is fork/exec'd by the debugger,
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the debugger should fork and the child should stop
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itself (with a self-inflicted
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.Dv SIGSTOP
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for example).
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The parent should issue a
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.Dv wait
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and then an
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.Dv attach
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command via the appropriate
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.Pa ctl
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file.
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The child process will receive a
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.Dv SIGTRAP
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immediately after the call to exec (see
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.Xr execve 2 ) .
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.Pp
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Each node is owned by the process's user, and belongs to that user's
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primary group, except for the
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.Pa mem
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node, which belongs to the
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.Li kmem
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group.
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.Sh FILES
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.Bl -tag -width /proc/curproc/XXXXXXX -compact
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.It Pa /proc
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normal mount point for the
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.Nm .
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.It Pa /proc/pid
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directory containing process information for process
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.Pa pid .
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.It Pa /proc/curproc
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directory containing process information for the current process
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.It Pa /proc/curproc/cmdline
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the process executable name
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.It Pa /proc/curproc/ctl
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used to send control messages to the process
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.It Pa /proc/curproc/etype
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executable type
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.It Pa /proc/curproc/file
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executable image
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.It Pa /proc/curproc/fpregs
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the process floating point register set
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.It Pa /proc/curproc/map
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virtual memory map of the process
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.It Pa /proc/curproc/mem
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the complete virtual address space of the process
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.It Pa /proc/curproc/note
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used for signaling the process
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.It Pa /proc/curproc/notepg
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used for signaling the process group
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.It Pa /proc/curproc/osrel
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the process osrel value
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.It Pa /proc/curproc/regs
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the process register set
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.It Pa /proc/curproc/rlimit
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the process current and maximum rlimit
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.It Pa /proc/curproc/status
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the process' current status
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.El
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.Sh EXAMPLES
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To mount a
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.Nm
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file system on
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.Pa /proc :
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.Pp
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.Dl "mount -t procfs proc /proc"
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.Sh SEE ALSO
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.Xr procstat 1 ,
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.Xr mount 2 ,
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.Xr sigaction 2 ,
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.Xr unmount 2 ,
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.Xr procctl 8 ,
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.Xr pseudofs 9
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.Sh AUTHORS
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.An -nosplit
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This manual page written by
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.An Garrett Wollman ,
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based on the description
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provided by
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.An Jan-Simon Pendry ,
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and revamped later by
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.An Mike Pritchard .
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