path: root/lib/libkvm/kvm_getprocs.3

.\"	$OpenBSD: kvm_getprocs.3,v 1.21 2019/08/11 15:48:08 deraadt Exp $
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.\"     @(#)kvm_getprocs.3	8.1 (Berkeley) 6/4/93
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.Dd $Mdocdate: August 11 2019 $
.Dt KVM_GETPROCS 3
.Os
.Sh NAME
.Nm kvm_getprocs ,
.Nm kvm_getargv ,
.Nm kvm_getenvv
.Nd access user process state
.Sh SYNOPSIS
.In sys/param.h
.In sys/sysctl.h
.In kvm.h
.Ft struct kinfo_proc *
.Fn kvm_getprocs "kvm_t *kd" "int op" "int arg" "size_t elemsize" "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"
.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 Dv KERN_PROC_KTHREAD
all processes (user-level plus kernel threads)
.It Dv KERN_PROC_ALL
all user-level processes
.It Dv KERN_PROC_PID
processes with process ID
.Fa arg
.It Dv KERN_PROC_PGRP
processes with process group
.Fa arg
.It Dv KERN_PROC_SESSION
processes with session
.Fa arg
.It Dv KERN_PROC_TTY
processes with
.Xr tty 4
.Fa arg
.It Dv KERN_PROC_UID
processes with effective user ID
.Fa arg
.It Dv KERN_PROC_RUID
processes with real user ID
.Fa arg
.El
.Pp
Only the first
.Fa elemsize
bytes of each array entry are returned.
If the size of the
.Vt kinfo_proc
structure increases in size in a future release of
.Ox ,
the library will only return the requested amount of data for
each array entry and programs that use
.Fn kvm_getprocs
will continue to function without the need for recompilation.
The number of processes found is returned in the reference parameter
.Fa cnt .
The processes are returned as a contiguous array of
.Vt kinfo_proc
structures, the definition for which is available in
.In sys/sysctl.h .
This memory is locally allocated, and subsequent calls to
.Fn kvm_getprocs
and
.Fn kvm_close
will overwrite this storage.
.Pp
.Fn kvm_getprocs
sets the thread ID field accordingly for each thread except for the
process (main thread) which has it set to \-1.
.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 execve 2
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
.Va 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
.Li argv
pointers and string storage is owned by the
.Xr kvm 3
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.
.Sh RETURN VALUES
.Fn kvm_getprocs ,
.Fn kvm_getargv ,
and
.Fn kvm_getenvv
all return
.Dv NULL
on failure.
.Sh SEE ALSO
.Xr kvm 3 ,
.Xr kvm_geterr 3 ,
.Xr kvm_nlist 3 ,
.Xr kvm_open 3 ,
.Xr kvm_read 3
.Sh BUGS
These routines do not belong in the
.Xr kvm 3
interface.