Manual browser: kvm_getenvv(3)

KVM_GETPROCS(3) Library Functions Manual KVM_GETPROCS(3)


kvm_getprocs, kvm_getargv, kvm_getenvvaccess user process state


Kernel Data Access Library (libkvm, -lkvm)


#include <kvm.h>
#include <sys/param.h>
#include <sys/sysctl.h>

struct kinfo_proc *
kvm_getprocs(kvm_t *kd, int op, int arg, int *cnt);

char **
kvm_getargv(kvm_t *kd, const struct kinfo_proc *p, int nchr);

char **
kvm_getenvv(kvm_t *kd, const struct kinfo_proc *p, int nchr);

struct kinfo_proc2 *
kvm_getproc2(kvm_t *kd, int op, int arg, int elemsize, int *cnt);

char **
kvm_getargv2(kvm_t *kd, const struct kinfo_proc2 *p, int nchr);

char **
kvm_getenvv2(kvm_t *kd, const struct kinfo_proc2 *p, int nchr);


kvm_getprocs() returns a (sub-)set of active processes in the kernel indicated by kd. The op and arg arguments constitute a predicate which limits the set of processes returned. The value of op describes the filtering predicate as follows:

all processes
processes with process id arg
processes with process group arg
processes with session id arg
processes with tty device arg
processes with effective user id arg
processes with real user id arg
processes with effective group id arg
processes with real group id arg

The number of processes found is returned in the reference parameter cnt. The processes are returned as a contiguous array of kinfo_proc structures. This memory is locally allocated, and subsequent calls to kvm_getprocs() and kvm_close() will overwrite this storage.

If the op argument for kvm_getprocs() is KERN_PROC_TTY, arg can also be KERN_PROC_TTY_NODEV to select processes with no controlling tty and KERN_PROC_TTY_REVOKE to select processes which have had their controlling tty revoked.

kvm_getargv() returns a null-terminated argument vector that corresponds to the command line arguments passed to process indicated by p. Most likely, these arguments correspond to the values passed to 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 kvm_getprocs().

The 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 ps(1) and 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 nchr is zero, no limit is imposed and all argument strings are returned in their entirety.

The memory allocated to the argv pointers and string storage is owned by the kvm library. Subsequent kvm_getprocs() and kvm_close(3) calls will clobber this storage.

The kvm_getenvv() function is similar to kvm_getargv() but returns the vector of environment strings. This data is also alterable by the process.

kvm_getproc2() is similar to kvm_getprocs() but returns an array of kinfo_proc2 structures. Additionally, only the first elemsize bytes of each array entry are returned. If the size of the kinfo_proc2 structure increases in size in a future release of NetBSD the kernel will only return the requested amount of data for each array entry and programs that use kvm_getproc2() will continue to function without the need for recompilation.

The kvm_getargv2() and kvm_getenvv2() are equivalents to the kvm_getargv() and kvm_getenvv() functions but use a kinfo_proc2 structure to specify the process.

If called against an active kernel, the kvm_getproc2(), kvm_getargv2(), and kvm_getenvv2() functions will use the sysctl(3) interface and do not require access to the kernel memory device file or swap device.


kvm_getprocs(), kvm_getargv(), kvm_getenvv(), kvm_getproc2(), kvm_getargv2(), and kvm_getenvv2() all return NULL on failure.


These routines do not belong in the kvm interface.
February 10, 2004 NetBSD 7.0