How to execute a psql command within a bash for loop

Question

I want to execute a psql statement within a bash script and output the results to a file. The code I have below works as desired:

#!/bin/bash

query=\"select         


        

Answer 1

You are overwriting the file each time with > inside the loop. You need >> inside or have > outside the loop:

#!/bin/bash

query="select * from mytable;"
for (( i=0; i<5; i++ ))
do
   psql <<EOF
   \timing
   $query
EOF
done > output.txt

Putting > after done is a little more efficient than >> inside the loop.

---

Similar post:

• Pass values read from a file as input to an SQL query in Oracle

Answer 2

It is usually better to not run Postgres in a loop. Just generate the commands you want to execute, then run the sequence of generated commands once.

#!/bin/bash

query="select * from mytable;"

for (( i=0; i<5; i++ ))
do
   cat <<___EOF
   \timing
   $query
___EOF
done |
psql > output.txt

which of course in this case can be simplified to just

#!/bin/bash
printf '-- %s\n\\timing\nselect * from mytable;\n' {1..5} |
psql >output.txt

The brace expansion {1..5} is Bash-specific, so you can't use sh for this particular snippet. (There is a difference.)