# 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 ‘script.sh,’ and write the following script in it:

- echo “Enter two numbers”
- read a.
- read b.
- sum=`expr $a + $b`
- 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.