[SOLVED] What is wrong with these If statements ?

pedropt · 06-30-2023, 12:08 PM

hello everyone , i can not figure out why this does not work correctly , need some help .

Example script ahead , execute it and set var1 as 0 and var2 as 1 and the output will say that are both at 1 !!!

Code:

#!/bin/bash
echo -n "Set Var 1 (0 or 1) : "
read -r var1
echo -n "Set Var 2 (0 or 1) : "
read -r var2


if [ "$var1" == "1" ] || [ "$var2" == "1" ]
then
echo "Both at 1"
elif [ "$var1" == "0" ] || [ "$var2" == "1" ]
then
echo "Var1 at 0 | var2 at 1"
elif [ "$var1" == "1" ] || [ "$var2" == "0" ]
then
echo "Var1 at 1 | var2 at 0"
elif [ "$var1" == "0" ] || [ "$var2" == "0" ]
then
echo "Both at 0"
fi
exit 0

michaelk · 06-30-2023, 12:14 PM

You need to use and (&&) instead of or (||)

pedropt · 06-30-2023, 12:18 PM

lol , yes , simple as that , i read somewhere that i could use || also , probably it is used for other purposes .

Thank you

teckk · 06-30-2023, 12:31 PM

&& and
|| or

michaelk · 06-30-2023, 01:11 PM

Binary logic
1 || 1 = 1
1 || 0 = 1
0 || 1 = 1
0 || 0 = 0

1 && 1 = 1
1 && 0 = 0
0 && 1 = 0
0 && 0 = 0

rknichols · 07-01-2023, 09:17 AM

Quote:

Originally Posted by michaelk

Binary logic
1 || 1 = 1
1 || 0 = 1
0 || 1 = 1
0 || 0 = 0

1 && 1 = 1
1 && 0 = 0
0 && 1 = 0
0 && 0 = 0

Unless you're talking about process return codes. For those, 0 indicates success ("True") and non-zero indicates failure ("False"). So,

True && False = False
True || False = True

ends up being effectively

0 && 1 = 1
0 || 1 = 0

Sometimes it's best not to think too much about what is actually happening under the hood.

Some say that the reason the Roman empire fell is that their numbering system did not include a zero, and thus their C programs had no way to indicate "success".