libutil: Improve kinfo_getproc(3) example and cross-references

Enhance the kinfo_getproc(3) manual page example:
- Make example work without arguments by defaulting to current process
  when no PID is specified
- Make memory output consistent by displaying all values in KB instead
  of mixing bytes and KB
- Add compilation instructions showing that -lutil is required

Improve struct documentation:
- Add comment about ki_structsize and KINFO_PROC_SIZE macro for
  determining actual structure size
- Direct readers to <sys/user.h> for full structure definition
- Move ellipsis inside comment to make struct syntactically valid C

Add cross-reference to kinfo_getproc(3) in libprocstat(3) manual page
since it provides comprehensive documentation for struct kinfo_proc.

Author: vstakhov

lib/libprocstat/libprocstat.3

@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 3, 2022
+.Dd November 4, 2025
 .Dt LIBPROCSTAT 3
 .Os
 .Sh NAME
@@ -577,6 +577,7 @@ argument indicates an actual error message in case of failure.
 .Xr shm_open 2 ,
 .Xr socket 2 ,
 .Xr elf 3 ,
+.Xr kinfo_getproc 3 ,
 .Xr kvm 3 ,
 .Xr queue 3 ,
 .Xr sem_open 3 ,

lib/libutil/kinfo_getproc.3

@@ -117,7 +117,8 @@ struct kinfo_proc {
 	struct	rusage ki_rusage;	/* process rusage statistics */
 	struct	rusage ki_rusage_ch;	/* rusage of children processes */
 	long	ki_sflag;		/* PS_* flags */
-	...				/* additional fields */
+	/* ... additional fields, see <sys/user.h> for full definition.
+	 * Use ki_structsize or KINFO_PROC_SIZE for actual struct size. */
 };
 .Ed
 .Pp
@@ -228,7 +229,8 @@ On failure the
 function returns
 .Dv NULL .
 .Sh EXAMPLES
-The following example retrieves and displays process memory information:
+The following example retrieves and displays process memory information.
+If no argument is provided, it displays information for the current process:
 .Bd -literal -offset indent
 #include <sys/types.h>
 #include <sys/user.h>
@@ -245,10 +247,10 @@ main(int argc, char *argv[])
 	int pagesize;
 	pid_t pid;
 
-	if (argc != 2)
-		errx(1, "usage: %s pid", argv[0]);
+	if (argc > 2)
+		errx(1, "usage: %s [pid]", argv[0]);
 
-	pid = atoi(argv[1]);
+	pid = (argc == 2) ? atoi(argv[1]) : getpid();
 	pagesize = getpagesize();
 
 	kp = kinfo_getproc(pid);
@@ -257,8 +259,8 @@ main(int argc, char *argv[])
 
 	printf("Process %d (%s) memory usage:\\n",
 	    kp->ki_pid, kp->ki_comm);
-	printf("  Virtual size: %zu bytes\\n",
-	    (size_t)kp->ki_size);
+	printf("  Virtual size: %zu KB\\n",
+	    (size_t)kp->ki_size / 1024);
 	printf("  Resident size: %zu KB\\n",
 	    (size_t)(kp->ki_rssize * pagesize) / 1024);
 	printf("  Text size: %zu KB\\n",
@@ -272,6 +274,11 @@ main(int argc, char *argv[])
 	return (0);
 }
 .Ed
+.Pp
+The above example can be compiled with:
+.Bd -literal -offset indent
+cc -o procmem procmem.c -lutil
+.Ed
 .Sh SEE ALSO
 .Xr ps 1 ,
 .Xr getpagesize 2 ,