Postgresql command execution in bash script

I have written a shell script to execute postgresql commands . Problem is when I am executing this script it is showing an error : line 17: psql: command not found

my script is as follows:

export PGPASSWORD=${PGPASSWORD-my_password}
echo "enter host"
read host
echo "enter database name"
read dbname
echo "enter username"
read username
psql -h $host $dbname $username <<EOF
SELECT * FROM test ; >>res.txt
EOF

( cat res.txt) | sed 's/;/<tab>/g' > $file.csv
rm res.txt
unset PGPASSWORD

Please suggest me what I am doing wrong .