Bash Shell Scripting For Beginners - Logical And & Logical Or

In this video we discuss the logical AND and the logical OR operators in bash.
you can get a more in depth explanation of these operators here
https://en.wikipedia.org/wiki/Logical_conjunction
Source code for the script used in this video
###Bash Logical Or and Logical And###
####Truth Tables###
# True True
# False False
# True and True True
# True and False and True and True . False
# False and True False
# False and False False
# True or True True
# True or False True
# False or True or False or False . True
# False or False False
true_vartrue
false_varfalse
#you don't have to compare a boolean variable to true, the below way is much better
if $true_var true; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
if $true_var; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
if $true_var; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
###Logical And
if $true_var && $false_var ; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
if $false_var && $false_var ; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
###Logical Or
if $true_var $false_var ; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
if $true_var $true_var ; then
echo 'This variable is true'
else
echo 'This variable is false'
fi
End First Script
realistic example of using and or
echo "enter you age"
read age
echo "are you a felon or are you innocent?"
read criminal_status
years$(expr 18 - $age)
if [ $age -ge 18 ] && [ $criminal_status "innocent" ]; then
echo 'You may purchase a firearm'
elif [ $age -le 18 ] && [ $criminal_status "innocent" ]; then
echo "You are too young kid, come back in ${years} years"
elif [ $age -le 18 ] && [ $criminal_status "felon" ]; then
echo "You are on a bad road kid, stay in school"
elif [ $age -ge 18 ] && [ $criminal_status "felon" ]; then
echo "You are a felon, we can't sell you a firearm!"
fi
End of second script
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