KVM_GETPROCS(3) FreeBSD 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>
#include < sys/user.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);


The kvm_getprocs() function 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 and kernel visible threads
all processes, without threads
processes with process ID arg
processes with process group arg
processes with session arg
processes with TTY arg
processes with effective user ID arg
processes with real user ID arg
modifier to return all kernel visible threads when filtering by process ID, process group, TTY, user ID, and real user ID

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.

The kvm_getargv() function 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.


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


These routines do not belong in the kvm interface.
November 22, 2011 FreeBSD