CODEWITHSUNDEEP
shell
Kintarō
Kintarō

Reputation: 3177

Extra single quote is appended in shell script

I am trying to write a simple script that loads the iptables rules from a file to the iptables:

#!/bin/bash
set -euxo pipefail
test_file="test.conf"
while read line; do
    echo $line
    echo "-----"
    iptables $line
done < $test_file

And the test.conf has some rules inside:

-A INPUT -p tcp -m tcp --dport 123 -m comment --comment "test 1" -j ACCEPT
-A INPUT -p tcp -m tcp --dport 112 -m comment --comment "test 2" -j ACCEPT
-A INPUT -p tcp -m tcp --dport 1231 -m comment --comment "test 3" -j ACCEPT

But when i run the script, it returns error as:

+ test_file=rules.conf
+ read line
+ echo -A INPUT -p tcp -m tcp --dport 123 -m comment --comment '"test' '1"' 
-j ACCEPT
-A INPUT -p tcp -m tcp --dport 123 -m comment --comment "test 1" -j ACCEPT
+ echo -----
-----
+ iptables -A INPUT -p tcp -m tcp --dport 123 -m comment --comment '"test' 
'1"' -j ACCEPT
Bad argument `1"'

Looks like whenever the file is run and if there is a space in the string, it will have a single quote to wrap around the space.

Is there a way to get rid of the behavior?

Upvotes: 0

Views: 35

Answers (1)

dgatwood
dgatwood

Reputation: 10407

The last line is the main problem. The shell doesn't interpret quote marks during variable expansion. If you change that to

eval iptables $line

you should get (roughly) the right results.

Your read statement is also potentially problematic because you didn't set IFS to a newline first. This could cause multiple whitespace to be collapsed and other possibly undesirable behavior. So I would start with

IFS="
"

or similar.

Upvotes: 1

Related Questions