How to check exit status of a command ?

$stat 
stat: missing operand
Try 'stat --help' for more information.
$echo $?
1
$stat popen1-p1.c 
  File: ‘popen1-p1.c’
  Size: 473       	Blocks: 8          IO Block: 4096   regular file
Device: 801h/2049d	Inode: 5245647     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/ jeffrin)   Gid: ( 1000/ jeffrin)
Access: 2014-06-16 23:31:58.746088758 +0530
Modify: 2014-06-16 23:31:27.649735653 +0530
Change: 2014-06-16 23:31:27.649735653 +0530
 Birth: -
$echo $?
0
$uname 
Linux
$echo $?
0
$uname -top
uname: invalid option -- 't'
Try 'uname --help' for more information.
$echo $?
1
$