There some useful preferences that you can set in your login.sql or glogin.sql that will help you use sqlplus inside your shell scripts.
set linesize 30000 : This is used to set the width of each page in your sql results
set pagesize 30000 : This is used to set how many line will be printed by page in your sql results
set pagesize 0: This set the pagesize to infinite
set wrap off : Truncates the line if its is longer then LINESIZE. This should not happen if linesize is large enough.
set trimspool on : Set it otherwise every line in the spoolfile is filled up with blanks until the linesize is reached.
set trimout on : Set it otherwise every line in the output is filled up with blanks until the linesize is reached.
set feedback off : To remove the "x lines were updated" at the end of sql results.
set verify off : Remove the variable substitution message
set heading off: Remove the heading of sql results
set colsep , : Separate columns with a comma
set newpage none : it will have the first blank line on sqlplus spool
All commands can be used in any sql file and in the interactive sqlplus prompt as well. But it if you always will use this configuration it is better to put in login.sql
or even glogin.sql
To remove some headers and footers when you login and logoff in sqlplus, use sqlplus -s option