syntax error in conditional expression

Question

I am writing a script where I am using the combination of logical 'OR' and logical 'AND' statement. This is the script:

#!/bin/bash echo "Enter the value of a" read $a echo "Enter the value of b" read $b if [[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then echo "Either of the JVMs is not yet up, so lets wait for some more time" i=$(($i+1)) sleep 1s fi 

and getting the following error while executing it:

line 13: syntax error in conditional expression line 13: syntax error near `]' line 13: `[[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then' 

I am using bash shell. Any help on this is really appreciated.

Answer 1

You have mismatched [[ with ]. [[ should always be closed with ]] and [ with ]. Use:

if [[ $a != STARTED && $b == STARTED ]] || [[ $b != STARTED && $a == STARTED ]]; then 

Better yet, since you are using [[ anyway:

if [[ ($a != STARTED && $b == STARTED) || ($b != STARTED && $a == STARTED) ]]; then 

The other mistake, which I didn't notice until formatting was applied, is that you're doing:

read $a read $b 

You should be doing:

read a read b 

With the first form, $a and $b are replaced by the shell with their contents, so if you hadn't set them before this line, the final command would be:

read 

(in which case the value read would be stored in the REPLY variable.) And if you had set a to something (like a="blah blah"), it would look like:

read blah blah 

Answer 2

Instead of:

[[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then 

I would use:

if [ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]; then