Shell Programming and Scripting

/usr/openv/volmgr/bin/vmquery -b -p 5

media   media  robot  robot  robot  side/  optical  # mounts/      last
 ID     type   type     #    slot   face   partner  cleanings    mount time
A01202  HCART  TLD      0     257     -       -          15     03/27/2016 07:29
A01262  HCART  TLD      0     361     -       -          31     05/20/2016 13:02
A01282  HCART  TLD      0      51     -       -          34     05/20/2016 15:21
KM3440  HCART  TLD      1      62     -       -         492     05/12/2016 00:55
KM3443  HCART  NONE     -      -     -       -         306     03/14/2014 16:37
KM3458  HCART  TLD      1     109     -       -         362     05/12/2016 05:40
KM3468  HCART  NONE     -      -     -       -           2     06/25/2015 15:21
KM3509  HCART  NONE     -      -     -       -          87     09/09/2014 06:01
LJY535  HCART  TLD      1     180     -       -         197     05/12/2016 11:48

/usr/openv/volmgr/bin/vmquery -b -p 5 | awk '$4==0{c++}END{print c}'

/usr/openv/volmgr/bin/vmquery -b -p 5 | awk '{n+=gsub(/^0$/,X,$4)} END{print n}'

/usr/openv/volmgr/bin/vmquery -b -p 5 | awk '$4==0{c++}END{print c}'

awk '$4==0      ##### It is a condition check(similar what we do in if else condition check). Where $4 means 4th field and we are checking here if 4th field is 0 or not.
{
c++             ##### If 4th field is having ZERO value then there is variable named C, so we are incrementing it's value by doing c++ to one.
}
END{            ##### Here starts END block, in awk there are 3 sections, i- BEGIN- if you want to perform some operations in very starting of your program. ii- Body- where we write actual logic/code for our requirements. iii- END- block code will be executed when all Inputs are read from Input_file. 
print c}'       ##### printing the value of variable c, which will tell us how many 4th fields have value 0 in them.