how to assign a query result to a shell variable

Question

I have an sql query that returns a date. I call this query from a shell script and would like to assign this value to the variable called datestart (and use it later). Here is my code. Without the datestart assignment the query works fine.

#!/bin/sh
firstname="-Upgsql"
dbname="statcoll"
portname="-p5438"
datestart=(psql $firstname $portname $dbname<< EOF
SELECT MIN(latestrefdate) FROM (SELECT MAX(referencedate) AS latestrefdate FROM statistics WHERE transactionname IN(SELECT DISTINCT transactionname FROM statistics WHERE platform = 'Smarties')GROUP BY transactionname) as earliest;
EOF
)
echo $datestart

but the result is this :

 Syntax error: word unexpected (expecting ")").

I have no idea where should I insert that closing bracket. Any hint is appreciated.

anubhava · Accepted Answer · 2014-06-16 14:42:04Z

2

Instead of brackets in variable assignment you need to use $(...) for BASH or `...` for sh.

Try this:

#!/bin/sh

firstname="-Upgsql"
dbname="statcoll"
portname="-p5438"
datestart=`psql -t --pset="footer=off" --user="$firstname" --port="$portname" -d "$dbname"<<EOF
SELECT MIN(latestrefdate) FROM (SELECT MAX(referencedate) AS latestrefdate FROM statistics WHERE transactionname IN (SELECT DISTINCT transactionname FROM statistics WHERE platform = 'Smarties') GROUP BY transactionname) as earliest;
EOF
`
echo "$datestart"

edited Jun 16, 2014 at 14:42

answered Jun 16, 2014 at 14:12

anubhava

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4 Comments

scragar Over a year ago

I really recommend $(..) over backticks, backticks don't work at all when used inside of each other, while nested expressions are fine using $(..)

Sanyifejű Over a year ago

yes, it almost solved my problem. Instead of the actual date value the content of the header gets assigned to the variable. So I expect something like this '2014-05-23' but got 'min ----- (1 row)' instead

anubhava Over a year ago

That is due to column header and footer text. See this Q&A

anubhava Over a year ago

Also check updated answer and this: stackoverflow.com/questions/9934264/…

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