bash variable substitution without single quotes - bash

Question

I have the following bash script for sending an email reports. I am trying to get it working correctly with mail command on bash and want to use variable substitution conditional which requires to use eval.
#!/bin/bash
LOG="/tmp/error.txt"
echo "test" > $LOG
INCLUDED="aaaaaaaaaaaaaaaaa"
EXCLUDED="bbbbbbbbbbbbbbbbb"
STR=INCLUDED
BODY="
Email Body:
\${!STR}"
#Set STR based on some condition
STR=EXCLUDED # set conditional with if statement
SUB="email subject"
PARAMS="-r \" Sender <ret#address.com>\""
PARAMS+=" -s \"$SUB\""
PARAMS+=" -A $LOG" # use conditional with if statement
eval echo \"MESSAGE: "${BODY}"\" | mail $(eval echo ${PARAMS}) "user#email.com"
While running the below code, I have to pass $PARAMS output without the quotes around the string as input to mail command, which does not recognise the diff options. The closest I can get to is using calling $(eval echo $PARAMS), but this garbels the subject since it remove the double quotes around the subject.
+ LOG=/tmp/error.txt
+ echo test
+ INCLUDED=aaaaaaaaaaaaaaaaa
+ EXCLUDED=bbbbbbbbbbbbbbbbb
+ STR=INCLUDED
+ BODY='
Email Body:
${!STR}'
+ STR=EXCLUDED
+ SUB='email subject'
+ PARAMS='-r " Sender <ret#address.com>"'
+ PARAMS+=' -s "email subject"'
+ PARAMS+=' -A /tmp/error.txt'
+ eval echo '"MESSAGE:' '
Email Body:
${!STR}"'
++ echo 'MESSAGE:
Email Body:
bbbbbbbbbbbbbbbbb'
++ eval echo -r '"' Sender '<ret#address.com>"' -s '$SUB' -A /tmp/error.txt
+++ echo -r ' Sender <ret#address.com>' -s email subject -A /tmp/error.txt
+ mail -r Sender '<ret#address.com>' -s email subject -A /tmp/error.txt user#email.com
How do I pass the $PARAMS to the mail command with passing the subject (-s) as quoted string ?

Answer 1

Use an array instead and put each string in an array element.
params=('-r')
params=("${params[#]}" ' Sender <ret#address.com>')
mail "${params[#]}"
Or simpler
params=('-r')
params+=(' Sender <ret#address.com>')
mail "${params[#]}"
See here: Bash: add value to array without specifying a key
Update, because I think you lack some fundamental shell programming knowledge.
Don't use eval! If you need to delay an evaluation, write a function, which performs the evaluation, when you call it.
Use single quotes for static strings and double quotes for strings containing variables.
Use arrays, if you need arrays.
Group commands in curly braces, if you need to group commands.
This is you example updated according to the rules above.
LOG=/tmp/error.txt
echo 'test' > $LOG
INCLUDED='aaaaaaaaaaaaaaaaa'
EXCLUDED='bbbbbbbbbbbbbbbbb'
STR=INCLUDED
body () { echo "
Email Body:
$STR"
}
#Set STR based on some condition
STR=EXCLUDED # set conditional with if statement
SUB='email subject'
PARAMS=('-r' 'Sender <ret#address.com>')
PARAMS+=('-s' "$SUB")
PARAMS+=('-A' "$LOG") # use conditional with if statement
{ echo -n 'MESSAGE: '; body; } | mail "${PARAMS[#]}" 'user#email.com'
You can test your code by putting a mail mock-up at the beginning of the program.
mail() { echo mail "$#"; cat; }