Question on bash script

I have some questions while digesting a bash script :

#1 does the line read the output from SQL and store in variable jobs
#2 does the line read the output from SQL and store in variable dbdata ?
      Why the syntax is different from #1
#3 What is the purpose of IFS="$( echo -e '\t' )" ? What does this line do ?

#1 read -ra jobs <<< $(SQL -h$SQL_HOST -u$SQL_USR -p$SQL_PWD cms -e "select id from Job where status='Pending' order by id;" | sed "1 d")

for ID in "${jobs[@]}";
  echo "ID=$ID" | tee -a ${_LOG}

  #2 dbdata=`SQL -h$SQL_HOST -u$SQL_USR -p$SQL_PWD cms -e "select * from Job where id=$ID;" | sed "1 d"`

  #3 IFS="$( echo -e '\t' )" read -ra jobinfo <<< "$dbdata"

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1)  Yes

2)  Yes.   The syntax is different, but the result is the same.

Originally, to capture the output of a command, you needed to use backticks, eg:


In newer shells, that syntax was superceded by  $(), eg:


The $() format is much easier to read as backticks can look like single quotes if you don't look carefully.

3)  This is an odd way of setting the IFS (Internal Field Separator) variable to a tab.  

It's the same as doing


This means that tabs are recognised as the separator between fields.

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Shell Scripting

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