if-statement incorrect output

Question

Here's the script.

#!/bin/bash

set -e
echo ""

declare -i value=00
unset optics_status

optics_status=$(curl -I xx.xx.xx.xx:4512 | grep 'X-Trace' | awk '{print $NF}' | rev |cut -c 1-3 | rev)


if [ $optics_status != $value ]; then
    echo "result is different means I am in if loop"
    echo "stats is $optics_status"
else
    echo "result is equal means I am in else loop"
    echo "stats is $optics_status"
fi

xx.xx.xx.xx is a server IP and if I run the curl command separately this is the output I get.

user@machine-lap:~/Documents$ curl -I xx.xx.xx.xx:4512 | grep 'X-Trace' | awk '{print $NF}' | rev |cut -c 1-3 | rev
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0  8359    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
00
user@machine-lap:~/Documents$

As you see I've set value to 00 and the output of optics_status is also 00. So according to the if loop, it should echo i am in else loop but it just echos the i am in if loop and I can't understand why.

To put it in simpler words, its echoing the if statement instead of else.

Answer 1

If you want your value variable to be 00, don't declare it as an integer in bash. Declaring it as an integer with declare -i will prompt the shell to evaluate it as an integer, and the integer value of 00 is zero.

Observe, the following code will output not same:

declare -i value='00'
optics_status='00'

if [ "$optics_status" = "$value" ]; then
   echo 'same'
else
   echo 'not same'
fi

Changing declare -i value='00' to value='00' will make it output same.

Also note the quoting of the variable expansions above.

---

You could of course also consider promoting both variables' values to integers by comparing them using either

if [ "$optics_status" -ne "$value" ]; then

or

if (( optics_status != value )); then

but that assumes that you know that $optics_value is always going to be a string that may be converted to an integer (and a decimal integer rather than an octal integer too).

Answer 2

cut's ranges are inclusive, so you've pulled three characters out. One of those characters might be invisible, such as a space, tab or newline. That makes the string different from the value 00.

In general, try set -o xtrace to see what happens when running your script. And Use More Quotes™!