Question

我在Linux控制台上打招呼;我想用整数变量

创建if语句

if[$x= [$#-2]]

但是如果can't find this statment if[1 = [5-2]]，控制台会收到请帮助我并纠正我的陈述。

Answer 1

您需要算术扩展：$((expression))

if [ $x = $(($# - 2)) ]; then
# ^ ^  ^ ^           ^ spaces are mandatory

Answer 2

开始$#是传递给bash脚本的参数数量

./bash_script 1 2 3

$#自动魔法填充到3.我希望你已经知道了。

#!/bin/bash
x=1
#If you are trying to compare `$x` with the value of the expression `$# - 2` below is how you do it :
if (( $x == $# - 2 ))
then
echo "Some Message"
fi
#If you are trying to check the assignment to `$x was successful below is how you do it :
if (( x = $# - 2 ))
then
echo "Some Message"
fi

第二个条件几乎总是如此，但第一个条件可能是假的。以下是我的测试结果：

#Here the both ifs returned true
sjsam@WorkBox ~/test
$ ./testmath1 1 2 3 
Some Message
Some Message
#Here the first if returned false because we passed 4 parameters
sjsam@WorkBox ~/test 
$ ./testmath1 1 2 3 4
Some Message

如何比较bash中的变量

2 个答案: