lib/libkvm/kvm_getprocs.3

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.\"     @(#)kvm_getprocs.3	8.1 (Berkeley) 6/4/93
.\"
.Dd January 9, 2018
.Dt KVM_GETPROCS 3
.Os
.Sh NAME
.Nm kvm_getprocs ,
.Nm kvm_getargv ,
.Nm kvm_getenvv ,
.Nm kvm_getproc2 ,
.Nm kvm_getargv2 ,
.Nm kvm_getenvv2
.Nd access user process state
.Sh LIBRARY
.Lb libkvm
.Sh SYNOPSIS
.In kvm.h
.In sys/param.h
.In sys/sysctl.h
.\" .Fa kvm_t *kd
.Ft struct kinfo_proc *
.Fn kvm_getprocs "kvm_t *kd" "int op" "int arg" "int *cnt"
.Ft char **
.Fn kvm_getargv "kvm_t *kd" "const struct kinfo_proc *p" "int nchr"
.Ft char **
.Fn kvm_getenvv "kvm_t *kd" "const struct kinfo_proc *p" "int nchr"
.Ft struct kinfo_proc2 *
.Fn kvm_getproc2 "kvm_t *kd" "int op" "int arg" "size_t elemsize" "int *cnt"
.Ft char **
.Fn kvm_getargv2 "kvm_t *kd" "const struct kinfo_proc2 *p" "int nchr"
.Ft char **
.Fn kvm_getenvv2 "kvm_t *kd" "const struct kinfo_proc2 *p" "int nchr"
.Sh DESCRIPTION
.Fn kvm_getprocs
returns a (sub-)set of active processes in the kernel indicated by
.Fa kd .
The
.Fa op
and
.Fa arg
arguments constitute a predicate
which limits the set of processes returned.
The value of
.Fa op
describes the filtering predicate as follows:
.Pp
.Bl -tag -width 20n -offset indent -compact
.It Sy KERN_PROC_ALL
all processes
.It Sy KERN_PROC_PID
processes with process id
.Fa arg
.It Sy KERN_PROC_PGRP
processes with process group
.Fa arg
.It Sy KERN_PROC_SESSION
processes with session id
.Fa arg
.It Sy KERN_PROC_TTY
processes with tty device
.Fa arg
.It Sy KERN_PROC_UID
processes with effective user id
.Fa arg
.It Sy KERN_PROC_RUID
processes with real user id
.Fa arg
.It Sy KERN_PROC_GID
processes with effective group id
.Fa arg
.It Sy KERN_PROC_RGID
processes with real group id
.Fa arg
.El
.Pp
The number of processes found is returned in the reference parameter
.Fa cnt .
The processes are returned as a contiguous array of
.Sy kinfo_proc
structures.
This memory is locally allocated, and subsequent calls to
.Fn kvm_getprocs
and
.Fn kvm_close
will overwrite this storage.
.Pp
If the
.Fa op
argument for
.Fn kvm_getprocs
is
.Sy KERN_PROC_TTY ,
.Fa arg
can also be
.Sy KERN_PROC_TTY_NODEV
to select processes with no controlling tty and
.Sy KERN_PROC_TTY_REVOKE
to select processes which have had their controlling tty
revoked.
.Pp
.Fn kvm_getargv
returns a null-terminated argument vector that corresponds to the
command line arguments passed to process indicated by
.Fa p .
Most likely, these arguments correspond to the values passed to
.Xr exec 3
on process creation.
This information is, however,
deliberately under control of the process itself.
Note that the original command name can be found, unaltered,
in the p_comm field of the process structure returned by
.Fn kvm_getprocs .
.Pp
The
.Fa nchr
argument indicates the maximum number of characters, including null bytes,
to use in building the strings.
If this amount is exceeded, the string
causing the overflow is truncated and the partial result is returned.
This is handy for programs like
.Xr ps 1
and
.Xr w 1
that print only a one line summary of a command and should not copy
out large amounts of text only to ignore it.
If
.Fa nchr
is zero, no limit is imposed and all argument strings are returned in
their entirety.
.Pp
The memory allocated to the argv pointers and string storage
is owned by the kvm library.
Subsequent
.Fn kvm_getprocs
and
.Xr kvm_close 3
calls will clobber this storage.
.Pp
The
.Fn kvm_getenvv
function is similar to
.Fn kvm_getargv
but returns the vector of environment strings.
This data is also alterable by the process.
.Pp
.Fn kvm_getproc2
is similar to
.Fn kvm_getprocs
but returns an array of
.Sy kinfo_proc2
structures.
Additionally, only the first
.Fa elemsize
bytes of each array entry are returned.
If the size of the
.Sy kinfo_proc2
structure increases in size in a future release of
.Nx
the kernel will only return the requested amount of data for
each array entry and programs that use
.Fn kvm_getproc2
will continue to function without the need for recompilation.
.Pp
The
.Fn kvm_getargv2
and
.Fn kvm_getenvv2
are equivalents to the
.Fn kvm_getargv
and
.Fn kvm_getenvv
functions but use a
.Sy kinfo_proc2
structure to specify the process.
.Pp
If called against an active kernel, the
.Fn kvm_getproc2 ,
.Fn kvm_getargv2 ,
and
.Fn kvm_getenvv2
functions will use the
.Xr sysctl 3
interface and do not require access to the kernel memory device
file or swap device.
.Sh RETURN VALUES
.Fn kvm_getprocs ,
.Fn kvm_getargv ,
.Fn kvm_getenvv ,
.Fn kvm_getproc2 ,
.Fn kvm_getargv2 ,
and
.Fn kvm_getenvv2
all return
.Dv NULL
on failure.
.Sh SEE ALSO
.Xr kvm 3 ,
.Xr kvm_close 3 ,
.Xr kvm_geterr 3 ,
.Xr kvm_nlist 3 ,
.Xr kvm_open 3 ,
.Xr kvm_openfiles 3 ,
.Xr kvm_read 3 ,
.Xr kvm_write 3
.Sh BUGS
These routines do not belong in the kvm interface.