getting syntax error at line 34 : `<<' unmatched in ksh script

问题

I have a shell script, when I execute it, I get the error

syntax error at line 34 : `<<' unmatched in ksh script

column_name=`sqlplus -s $BASE_DB_CONN<<!!
    WHENEVER SQLERROR exit ROLLBACK
    set SQLPROMPT ''
    set heading off
    set pagesize 1000
    set linesize 5000
    set feedback off
    set define on
    set verify off
    @smm9_stream_map.sql $STREAM_NAME $FIELD_NAME"
    exit
    !!`;

To my surprise the same thing works in the while loop altered script as below

while [ $a -lt ${NO_LOOP} ]
do
column_name=`sqlplus -s $BASE_DB_CONN<<!!
    WHENEVER SQLERROR exit ROLLBACK
    set SQLPROMPT ''
    set heading off
    set pagesize 1000
    set linesize 5000
    set feedback off
    set define on
    set verify off
    @smm9_stream_map.sql $STREAM_NAME $FIELD_NAME"
    exit
    !!`;
a=`expr $a + 1`
done

Why does the second script work but not the first one?

回答1:

The heredoc terminator must be the only text on that line, no other whitespace allowed (*)

column_name=$(sqlplus -s $BASE_DB_CONN<<!!
    ....
    exit
!!
)

(*) the exception being, for heredocs using <<-, any leading tabs will be stripped from the heredoc, including from the terminator. I see in my ksh93 man page:

If # is appended to <<, then leading spaces and tabs will be stripped off the first line of the document and up to an equivalent indentation will be stripped from the remaining lines and from word.

来源：https://stackoverflow.com/questions/20186743/getting-syntax-error-at-line-34-unmatched-in-ksh-script