Error while using (( ... )) in Bash if condition

Question

#!/bin/bash
A='';B='';C='';D=''
function returnFunctionWebService()
{
        touch test.json
        curl http://localhost:9099/BelattarProject/StudentMail.php -o test.json
        for line in `cat test.txt`;do
                echo $line
                A=$(echo $line | cut -d ',' -f1)
                echo $A
                B=$(echo $line | cut -d ',' -f2)
                echo $B
                C=$(echo $line | cut -d ',' -f3)
                echo $C
                D=$(echo $line | cut -d ',' -f4)
                echo $D
        done
}
returnFunctionWebService
echo $A $B $C $D
if [ -n $A ]; then
        if(( "$A" = "\"test1\"" )); then
                echo -e "c'est juste"
                exit
        else
                echo -e "c'est pas juste"
                exit
        fi
fi

i have an error at this end which is ./scriptWeb.sh: line 22: ((: "test1" = "test1" : syntax error: operand expected (error token is ""test1" = "test1" ") some help please

Apart from using the wrong brackets, you must have whitespace between the `if` and the first open bracket. — cdarke, Mar 04 '18 at 20:57

codeforester · Answer 1 · 2018-03-04T18:13:44.170

4

(( )) can only be used for integer arithmetic, not for string comparisons. For strings, use [[ ]] construct, this way:

if [[ "$A" = "\"test1\"" ]]; then

There are many issues in your script. Get it checked at shellcheck

See also:

How to use double or single brackets, parentheses, curly braces

edited Mar 04 '18 at 18:13

answered Mar 04 '18 at 17:37

codeforester

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4

@RavinderSingh13 No, `=` indeed does string comparison :) – PesaThe Mar 04 '18 at 17:40
@PesaThe, really, could you please paste me the link(I will also learn from it) :), honestly didn't know it. – RavinderSingh13 Mar 04 '18 at 17:45
2

@RavinderSingh13 Many results if you search "bash compare string". https://askubuntu.com/questions/351765/bash-if-statement-compare-two-strings – llllllllll Mar 04 '18 at 17:47
i still have the same problem it dosen't solve it yet ^^ – Omar Amaoun Mar 04 '18 at 17:49
1

Not just "should"; it can *only* be used for arithmetic. `((...))` is the arithmetic compound command. – chepner Mar 04 '18 at 18:12
2

@OmarAmaoun If you made this change, you should not have the *same* problem. However, your script has many other problems that you need to work through. Follow thatotherguy's advice and use `jq` to parse json, and codeforster's advice to use shellcheck.net to spot common script errors. Also, read the answers to ["How to debug a bash script?"](https://stackoverflow.com/questions/951336/how-to-debug-a-bash-script/), and look through the many in the [bash tag info entry](https://stackoverflow.com/tags/bash/info). – Gordon Davisson Mar 04 '18 at 21:49

Error while using (( ... )) in Bash if condition

1 Answers1