Shell Programming and Scripting

wrkvar=`sqlplus -s / as sysdba <<EOF
set echo off feedback off head off trimsp on
select count(*) from v\$parameter
where name in ('db_file_name_convert','log_file_name_convert')
and value is not null;
EOF`
echo wrkvar=$wrkvar

wrkvar=select count(*) from v db_refresh db_refresh.sav doit ERROR at line 1: ORA-00942: table or view does not exist

wrkvar=$(sqlplus -s / as sysdba <<EOF
set echo off feedback off head off trimsp on
select count(*) from v\$parameter
where name in ('db_file_name_convert','log_file_name_convert')
and value is not null;
EOF)
echo wrkvar=$wrkvar

wrkvar= 2

bash-3.1$
bash-3.1$ abc="kkjhkjhkjhkj"
bash-3.1$ echo ` echo a\b v\$abc`
ab vkkjhkjhkjhkj
bash-3.1$ echo $( echo a\b v\$abc)
ab v$abc
bash-3.1$ echo ` echo a\b v\\$abc`
ab v$abc
bash-3.1$
bash-3.1$

       The format of here-documents is:

              <<[-]word
                      here-document
              delimiter

       No parameter expansion, command substitution, arithmetic expansion, or pathname expansion is
       performed  on  word.   If  any characters in word are quoted, the delimiter is the result of
       quote removal on word, and the lines in the here-document are  not  expanded.   If  word  is
       unquoted,  all lines of the here-document are subjected to parameter expansion, command sub‐
       stitution, and arithmetic expansion.  In the latter case, the character sequence  \<newline>
       is ignored, and \ must be used to quote the characters \, $, and `.