bash awk file compare

Question

I have a config
[LogicalUnit1]  UnitInquiry "NFSN00Y5IP51ZL"  LUN0 /mnt/extent0 64MB
[LogicalUnit2]  UnitInquiry "NFSN00N49CQL28"  LUN0 /mnt/extent1 64MB
[LogicalUnit3]  UnitInquiry "NFSNBRGQOCXK"  LUN0 /mnt/extent4 10MB
[LogicalUnit4]  UnitInquiry "NFSNE7IXADFJ"  LUN0 /mnt/extent5 25MB

which is read via a bash script, using awk i parse the file and get variables

    awk '/UnitInquiry/ {print $1, $3, $5, $6}' $ctld_config | while read a b c d ; do
        if [ -f $a ]
        then
              ctladm create -b block -o file=$c -S $b -d $a
              ctladm devlist -v > $lun_config
        else
              truncate -s $d $c ; ctladm create -b block -o file=$c -S $b -d $a
        fi

this will initialize the luns properly on bootup, however if i add a lun then it will recreate them all again, how can i compare whats running, to whats configured and only reinitialize the ones not already live, there is a command to list the devices

ctladm devlist -v
LUN Backend       Size (Blocks)   BS Serial Number    Device ID       
  0 block                131072  512 "NFSN00Y5IP51ZL  [LogicalUnit1]  
      lun_type=0
      num_threads=14
      file=/mnt/extent0
  1 block                131072  512 "NFSN00N49CQL28  [LogicalUnit2]  
      lun_type=0
      num_threads=14
      file=/mnt/extent1
  2 block                 20480  512 "NFSNBRGQOCXK"   [LogicalUnit3]  
      lun_type=0
      num_threads=14
      file=/mnt/extent4
  3 block                 51200  512 "NFSNE7IXADFJ"   [LogicalUnit4]  
      lun_type=0
      num_threads=14
      file=/mnt/extent5

Answer 1

Why not add the following after the then :

ctladm devlist -v | grep -q "$a" && continue

This will

• run the command that show the currently active devices
• check if the LogicalUnit name you want to register is already listed, and if yes...
• skip the rest of the loop.

If $a (logical unit name) is not unique enough, you can also grep for another, more unique identifier, eg the serial number.