When evaluating both arguments with null values, both the Logical OR and AND operators return 0. So, as said earlier, if the first argument is null, the second argument is returned. Reading that you may still have a couple of questions: What's the purpose of using empty double quotes ("") in the expression?Įmpty double quotes represent a null value in bash. The above screenshot represents operations with logical OR operator (|). (Empty string is considered as null in terminal)Įxpr 100 \| 78 # Returns first argument 100Įxpr "" \| "" # Returns 0 as both arguments are null ("") Terminal commands to evaluate logical OR expressions Evaluating logical OR expressions with expr command Let's examine few examples with the logical OR operator: expr 1 \| 2 # Returns first argument (1)Įxpr 0 \| 2 # Returns second argument (2) as first argument is 0Įxpr "" \| 2 # Returns second argument (2) as first argument is null On the other hand, evaluating expr ARG1 & ARG2 returns ARG1 if neither of the arguments are null or 0. This command will never return 1 if an expression evaluates to true – instead it returns an argument.Įvaluating expr ARG1 | ARG2 returns ARG1 if ARG1 is neither null nor 0, otherwise it'll return ARG2. But there's an exception for a particular case. The expr command works similar to the above table. Xīut they have a completely different usage with the expr command. For those people, replace FALSE with 0 and TRUE with 1. Some people may be familiar with 1 and 0. The OR operator evaluates to true if either of the sides evaluates to true. What are the special logical operators?".įrom a programming perspective, the AND operator evaluates to true if both sides of the operator evaluates to true.
You're thinking, "I know about logical operators. What Do the Special Logical Operators Do? The command returns "1" if the expression evaluates to true and "0" if it evaluates to false.įrom the above commands you can notice that all the logical operators are escaped with a backward slash (\). Let's have a quick look at how it works: expr 2 \ 23820Įxpr 293202 \!= 293203 Evaluate logical expressions with expr command Evaluate logical expressions with expr command Search results by Yahoo for the given expressionīut my terminal and system calculator were almost instant in finding the answer (took, >=, =, != can be evaluated with this command. Yahoo gave us the answer in less than 500 ms along with 1,480,000,000 search results. Search results by Google for the given expression Searching this expression on Google took less than a second to get the answer (using a 500MBPS connection) along with 5,21,00,000 results. So what if you used your browser to find the answer? How long would that take? I'm sure you'll be angry with me, though, after discovering that the result of this long expression just evaluated to zero. Kudos to you if you solved it on your own.
Can you solve the below math expression on your own without using any device? Take as much time as you need – but no tools allowed: ( ( 11 + 97 ) + ( 2 * 63 ) - ( 7 / 93 ) * ( 8 - 25 ) / ( 9 * 64 ) ) * ( ( 64 / 34 ) + ( 94 - 20 ) - ( 23 + 98 ) * ( 199 * 928 ) / ( 92 * 26 ) ) * ( ( ( 2 * 1 ) / 2 ) - 1 ) Long mathematical expression
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