bash 如何检查一个数字是否在shell中的范围内
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How to check if a number is within a range in shell
提问by Hyman
I want to just insert number between two values, and otherwise the script repeated until correct number.
我只想在两个值之间插入数字，否则脚本会重复直到正确的数字。
This is my script and it is not work correctly:
这是我的脚本，它不能正常工作：
validation(){
read number
if [ $number -ge 2 && $number -ls 5 ]; then
echo "valid number"
break
else
echo "not valid number, try again"
fi
}
echo "insert number"
validation
echo "your number is" $number
采纳答案by codeforester
If you are using Bash, you are better off using the arithmetic expression, ((...))for readability and flexibility:
如果您使用 Bash，((...))为了可读性和灵活性，最好使用算术表达式：
if ((number >= 2 && number <= 5)); then
# your code
fi
To read in a loop until a valid number is entered:
循环读取直到输入有效数字：
#!/bin/bash
while :; do
read -p "Enter a number between 2 and 5: " number
[[ $number =~ ^[0-9]+$ ]] || { echo "Enter a valid number"; continue; }
if ((number >= 2 && number <= 5)); then
echo "valid number"
break
else
echo "number out of range, try again"
fi
done
((number >= 2 && number <= 5))can also be written as ((2 <= number <= 5)).
((number >= 2 && number <= 5))也可以写成((2 <= number <= 5))。
See also:
也可以看看：
回答by sergio
Your if statement:
您的 if 语句：
if [ $number -ge 2 && $number -ls 5 ]; then
should be:
应该：
if [ "$number" -ge 2 ] && [ "$number" -le 5 ]; then
Changes made:
所做的更改：
- Quoting variables is considered good practice.
lsis not a valid comparison operator, usele.- Separate single-bracket conditional expressions with
&&.
- 引用变量被认为是很好的做法。
ls不是有效的比较运算符，请使用le.- 用
&&.分隔单括号条件表达式。
Also you need a shebang in the first line of your script: #!/usr/bin/env bash
您还需要在脚本的第一行中有一个 shebang： #!/usr/bin/env bash
回答by Diego Torres Milano
if [ $number -ge 2 && $number -ls 5 ]; then
should be
应该
if [[ $number -ge 2 && $number -le 5 ]]; then
see help [[for details
看help [[详细内容
回答by Jayesh Dhandha
2 changes needed.
需要进行 2 次更改。
Suggested by Sergio.
if [ "$number" -ge 2 ] && [ "$number" -le 5 ]; thenThere is no need of
break.only meaningful in a for, while, or until loop
由塞尔吉奥推荐。
if [ "$number" -ge 2 ] && [ "$number" -le 5 ]; then没有必要
break。only meaningful in a for, while, or until loop
