DB2 stored procedure (with input parameters) from script

I have a db2 stored procedure on my database which require 3 parameters, I have the following db2 command in a sql script

    CONNECT TO SAMPLE;
   CALL BACKUP(INPUT_1, INPUT_2, INPUT3);

Usually, I would just invoke this sql script from my shell script like below

    db2 -tf my_sql_script.sql -z logfile.txt

However, how can I pass these 3 user input parameters from shell script to my sql script? Can this be done?

If not, I can simple call invoke these sql command directly in my shell script, but how would I redirect all the messages from executing my DB2 stored procedure to a log file?

Thanks in advance!

If your .sql file always contain this two line only ??? then
you can write a function in unix script like this -

function ExecuteDB2Proc
{
Dname=$1
INPUT_1=$2
INPUT_2=$3
INPUT_3=$4
db2cmd="CALL BACKUP('$INPUT_1', '$INPUT_2', '$INPUT3')"
connect to $Dname
db2 +c -tv "${db2cmd}";>>log_file
}

##### call the above function using.....
ExecuteDB2Proc SAMPLE VALUE1 VALUE2 VALU3