bash scripting - how to use results from a function that is called as a variable

Question

Trying to figure out how to pass results of one function to another (as a variable). Below is the script I am working on:

#!/usr/local/bin/bash

set -x
_creds=/path/access
_pgpw=$(getPW)

getPW(){ 
  masterpw=$(grep -E 'url.*myfooapp.com' -A4 ${_creds}/access.json \
  | grep "pwd" \
  | awk '{split($0,a,":"); print a[2]}' \
  | grep -o '".*"' \
  | tr -d '"')
}

runQuery(){
  PGPASSWORD="${_pgpw}" \
  psql -h myfooapp.com -U masteruser -d dev -p 5439 
  echo "CLUSTER: ${_cluster}"
}

runQuery
set -x

What I need is PGPASSWORD to get the results from function getPW and its returning empty. I'm not sure if I did this correctly with the variable _pgpw=$(getPW) with trying to call a function. Please advise on best way to accomplish this. Thanks

getPW creates a global variable named masterpw; it doesn't emit any stdout at all. However, _pgpw=$(getPW) is assigning the empty stdout of getPW to _pgpw.. so you're ending up with a populated variable named masterpw, and an empty variable named _pgpw. Or, rather, that's what you would be ending up with if you put the function definition above the invocation. — Charles Duffy
– Charles Duffy, Commented Jul 10, 2018 at 23:42
If you want the output of getPW to be assigned to _pgpw, then take out the masterpw=$( from the front of the function definition's body, and the ) from the end, to stop redirecting that content into a FIFO used to assign masterpw, and thus away from the stdout content available for the command substitution used to assign _pgpw. — Charles Duffy
– Charles Duffy, Commented Jul 10, 2018 at 23:45
@CharlesDuffy - thank you for your input and breaking that down for me. Very informative. It works :-) — noober
– noober, Commented Jul 11, 2018 at 0:29

Grisha Levit · Accepted Answer · 2018-07-10 23:33:43Z

1

Bash executes a script line by line as it reads it. You need to define the function first, then call it. As your script is written, getPW is called before it is defined so it is not producing any output. Just move the _pgpw=$(getPW) line below the getPW() definition.

answered Jul 10, 2018 at 23:33

Grisha Levit

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chepner · Accepted Answer · 2018-07-10 13:07:42Z

1

Functions can take arguments; they are accessed inside the function via the positional parameters $1, $2, etc.

runQuery () {
    PGPASSWORD=$1
    psql ...
}

runQuery "$(getPW)"

answered Jul 10, 2018 at 13:07

chepner

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2 Comments

noober Over a year ago

thanks for your input. I ran exactly as you showed with $1. I am still getting prompted for password as its still showing empty. From the debug I can see masterpw is being extracted, but just not populated for PGPASSWORD. ++ masterpw='123456!@#' + runQuery '' + PGPASSWORD=

chepner Over a year ago

psql doesn't have support an environment variable analogous to PGUSER et al. for the password. You need to use a .pgpass file to store the password, or use a connection string instead of individual options; see e.g. postgresql.org/docs/9.3/static/libpq-connect.html for more details.

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