Manual Page Search Parameters
KVM_GETPROCS(3) Library Functions Manual KVM_GETPROCS(3)

kvm_getprocs, kvm_getargv, kvm_getenvv — access user process state

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

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

() 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 (user-level plus kernel threads)
all user-level processes
processes with process ID arg
processes with process group arg
processes with session arg
processes with tty(4) arg
processes with effective user ID arg
processes with real user ID arg

Only the first elemsize bytes of each array entry are returned. If the size of the kinfo_proc structure increases in size in a future release of OpenBSD, the library will only return the requested amount of data for each array entry and programs that use () will continue to function without the need for recompilation. The number of processes found is returned in the reference parameter cnt. The processes are returned as a contiguous array of kinfo_proc structures, the definition for which is available in <sys/sysctl.h>. This memory is locally allocated, and subsequent calls to kvm_getprocs() and () will overwrite this storage.

() sets the thread ID field accordingly for each thread except for the process (main thread) which has it set to -1.

() 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 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 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(3) library. Subsequent () and kvm_close(3) calls will clobber this storage.

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

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

kvm(3), kvm_geterr(3), kvm_nlist(3), kvm_open(3), kvm_read(3)

These routines do not belong in the kvm(3) interface.

August 11, 2019 openbsd