Use of read in the shell

read [parameter] [variable name]

Read-p "Please input a number:" Var

Read-t 10-p "Please input a number:" Var

#!/bin/sh

While True

Do

Read-t 10-p "Please input number:" A B

Expr $a + 0 >/dev/null 2>&1

[$?-ne 0] && continue

Expr $b + 0 >/dev/null 2>&1

[$?-ne 0] && continue| | Break

Done

echo "A-B =$ (($a-$b))"

echo "A+b =$ (($a + $b))"

echo "A*b =$ (($a * $b))"

echo "A/b =$ (($a/$b))"

echo "A**b =$ (($a * * $b))"

echo "A%b =$ (($a% $b))"

To pass the parameter:

[email protected] shell]# cat read1.sh

#!/bin/sh

A= "$"

B= "$"

Usage () {

echo "Usage:sh $ NUM1 num2"

Exit 1

}

If [$#-ne 2];then

Usage

Fi

Expr $a + 0 >/dev/null 2>&1

[$?-ne 0] && Usage

Expr $b + 0 >/dev/null 2>&1

[$?-ne 0] && Usage

echo "A-B =$ (($a-$b))"

echo "A+b =$ (($a + $b))"

echo "A*b =$ (($a * $b))"

echo "A/b =$ (($a/$b))"

echo "A**b =$ (($a * * $b))"

echo "A%b =$ (($a% $b))"

Use of read in the shell