How do you do subtraction in shell?

How do you do subtraction in shell?

The following arithmetic operators are supported by Bourne Shell….Unix / Linux – Shell Arithmetic Operators Example.

Operator Description Example
– (Subtraction) Subtracts right hand operand from left hand operand `expr $a – $b` will give -10

How do I negate if condition in shell script?

Negation When we use the not operator outside the [[, then it will execute the expression(s) inside [[ and negate the result. If the value of num equals 0, the expression returns true. But it’s negated since we have used the not operator outside the double square brackets.

How do you use expr in shell?

We can also perform operations on a variable by using a shell script. For example, let’s create a script for adding two numbers….Create a file ‘,’ and write the following script in it:

  1. echo “Enter two numbers”
  2. read a.
  3. read b.
  4. sum=`expr $a + $b`
  5. echo “Sum = $sum”

Does bash do subtraction?

Bash has the capability to perform mathematical integer calculations on variables straight from the command line of from within a script. Operations such as Addition, Subtraction, Division, Multiplication, Modulus and exponentiation calculations can be performed with ease.

What is BC in shell script?

BC, which stands for Basic Calculator, is a command in Bash that is used to provide the functionality of a scientific calculator within a Bash script.

What is opposite of =~ in bash?

There is no opposing operator in bash up to version 4.3 (current at the time of this post). [[ ! str1 =~ str2 ]] is the way to go.

What is expr in bash scripting?

The “expr” or expression instruction has been very well-known among bash users to evaluate certain expressions and give the results. These expressions contain more than 1 argument within. The expression could be of any type, i.e., string, integer, or regex.

How do you use expr multiplication?

To multiply using expr command use the \* operator. The following example will do multiplication by using the \* operator with expr command.

Do calculations in bash?

Bash Math Commands and Methods

  • Arithmetic Expansion. The preferable way to do math in Bash is to use shell arithmetic expansion.
  • awk Command. The awk command acts as a selector for pattern expressions.
  • bc Command.
  • dc Command.
  • declare Command.
  • expr Command.
  • factor Command.
  • let Command.

What is $@ and $* in SHell script?

The $@ holds list of all arguments passed to the script. The $* holds list of all arguments passed to the script.

How do you negate an IF IF statement?

So the negation of “X is true if and only if Y is true” is “Either X is true and Y is false, or X is false and Y is true.” Added: as it happens, as noted by Rahul Narain in his comment, this is in turn equivalent to “X is true if and only if Y is false” (just compare the cases when they are each true).

How do you negate an if statement?

To negate a statement of the form “If A, then B” we should replace it with the statement “A and Not B”. This might seem confusing at first, so let’s take a look at a simple example to help understand why this is the right thing to do.