双括号(())和 中括号[ ]在做整数运算时的效果是一样的？

274920831

两个脚本：
1.
#!/bin/bash
num=1
while [ "$num" -le 10 ]; do
echo "num is $num"
num=$(($num + 1))
done

2.
#!/bin/bash
num=1
while [ "$num" -le 10 ]; do
echo "num is $num"
num=$[$num + 1]
done

两个脚本的输出是一样的：
是不是说明 双括号(())和 [ ]在做整数运算时的效果是一样的？

cao627

((a++))
echo $a
[ b++ ]
echo $b

waker

$[] 和$(())是一样的，不过已经过时了

1. 
   
2. $[ ... ]
   
3. integer expansion.
   
4. 
   
5. Evaluate integer expression between $[ ].
   
6. a=3
   
7. b=7
   
8. 
   
9. echo $[$a+$b]   # 10
   
10. echo $[$a*$b]   # 21
    
11. 
    
12. Note that this usage is deprecated, and has been replaced by the (( ... )) construct.
    

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http://www.tldp.org/LDP/abs/html/special-chars.html