Verify the integer input

Gets the value of the variable excluding the first digit

${变量#?} Used to get the first value of the variable

number="123"
echo ${number#?}

23

Get the first bit of a variable

KaTeX parse error: Expected '}', got 'EOF' at end of input: {变量%{变量#?}} You can get the first bit of a variable

number="123"
echo ${number%${number#?}}

1

Filter numbers in variables

[[:digit:]]表示数字

echo $testvalue | sed ‘s/[[:digit:]]//g’

判断变量是否为空

-z 判断变量是否为空, 为空则返回true

if [ ! -z $nodigits ]

#!/bin/bash

valdint(){
    
number="$1"; min="$2"; max="$3"
if [ -z $number ]; then
 echo "Please enter the corresponding parameters">&2
 return 1
fi

if [ "${number%${number#?}}" = "-" ]; then
 testvalue="${number#?}"
else
 testvalue="$number"
fi

nodigits="$(echo $testvalue | sed 's/[[:digit:]]//g' )"

if [ ! -z $nodigits ]; then
 echo "只能输入数字">&2
 return 1
fi

if [ ! -z $min ] ; then
 if [ "$number" -lt "$min" ]; then
  echo "your value is too small,必须大于最小值">&2
 return 1
 fi
fi

if [ ! -z $max ] ; then
 if [ "$number" -gt "$max " ]; then
  echo "Your value is too large,必须小于最大值">&2
 return 1
 fi
fi
 return 0
}

if valdint "$1"  "$2"  "$3" ; then
 echo "The number you entered is valid"
fi