freebsd-src/lib/libkvm/kvm_getprocs.3

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.Dd November 22, 2011
.Dt KVM_GETPROCS 3
.Os
.Sh NAME
.Nm kvm_getprocs ,
.Nm kvm_getargv ,
.Nm kvm_getenvv
.Nd access user process state
.Sh LIBRARY
.Lb libkvm
.Sh SYNOPSIS
.In kvm.h
.In sys/param.h
.In sys/sysctl.h
.In sys/user.h
.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"
.Sh DESCRIPTION
The
.Fn kvm_getprocs
function 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_ALL
all processes and kernel visible threads
.It Dv KERN_PROC_PROC
all processes, without threads
.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 TTY
.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
.It Dv KERN_PROC_INC_THREAD
modifier to return all kernel visible threads when filtering
by process ID, process group, TTY, user ID, and real user ID
.El
.Pp
The number of processes found is returned in the reference parameter
.Fa cnt .
The processes are returned as a contiguous array of kinfo_proc structures.
This memory is locally allocated, and subsequent calls to
.Fn kvm_getprocs
and
.Fn kvm_close
will overwrite this storage.
.Pp
The
.Fn kvm_getargv
function 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.
.Sh RETURN VALUES
The
.Fn kvm_getprocs ,
.Fn kvm_getargv ,
and
.Fn kvm_getenvv
functions 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.