The meteor(4) man page includes 3 code examples for the 3 different modes of capture. The first two are complete and compile without any problems, but the third throws errors about undeclared variables.

I presume there is a line or two that was not correctly copied and pasted from the original source when preparing the man page.

Here's the output of 'gcc skeleton_capture_n.c'

In file included from skeleton_capture_n.c:5:
/usr/include/machine/ioctl_meteor.h:35:2: warning: #warning Include dev/bktr/ioctl_meteor.h instead of this header.
skeleton_capture_n.c: In function 'usr2_catcher':
skeleton_capture_n.c:23: error: 'sig_cnt' undeclared (first use in this function)
skeleton_capture_n.c:23: error: (Each undeclared identifier is reported only once
skeleton_capture_n.c:23: error: for each function it appears in.)
skeleton_capture_n.c:31: error: expected expression before ')' token
skeleton_capture_n.c: In function 'main':
skeleton_capture_n.c:51: error: 'i' undeclared (first use in this function)
skeleton_capture_n.c:52: warning: incompatible implicit declaration of built-in function 'printf'
skeleton_capture_n.c:53: warning: incompatible implicit declaration of built-in function 'exit'
skeleton_capture_n.c:55: warning: incompatible implicit declaration of built-in function 'printf'
skeleton_capture_n.c:59: error: expected expression before ';' token
skeleton_capture_n.c:66: warning: incompatible implicit declaration of built-in function 'exit'
skeleton_capture_n.c:69: error: 'c' undeclared (first use in this function)
skeleton_capture_n.c:73: warning: incompatible implicit declaration of built-in function 'exit'
skeleton_capture_n.c:80: warning: incompatible implicit declaration of built-in function 'exit'
skeleton_capture_n.c:91: error: 'y' undeclared (first use in this function)
skeleton_capture_n.c:96: error: 'struct meteor_capframe' has no member named 'signal'
skeleton_capture_n.c:103: warning: incompatible implicit declaration of built-in function 'exit'
skeleton_capture_n.c:113: warning: incompatible implicit declaration of built-in function 'exit'

Fix: 

Find the missing source lines. :)
How-To-Repeat: Copy and paste the source from the section " 3.   Memory mapped, multi-frame ring buffer synchronize capture." on the meteor(4) man page to a file; attempt to compile it.