Shell 字符串運(yùn)算范例

2021-08-31 09:27 更新
下面是一個(gè)例子,它使用的所有字符串運(yùn)算:
#!/bin/sh

a="abc"
b="efg"

if [ $a = $b ]
then
   echo "$a = $b : a is equal to b"
else
   echo "$a = $b: a is not equal to b"
fi

if [ $a != $b ]
then
   echo "$a != $b : a is not equal to b"
else
   echo "$a != $b: a is equal to b"
fi

if [ -z $a ]
then
   echo "-z $a : string length is zero"
else
   echo "-z $a : string length is not zero"
fi

if [ -n $a ]
then
   echo "-n $a : string length is not zero"
else
   echo "-n $a : string length is zero"
fi

if [ $a ]
then
   echo "$a : string is not empty"
else
   echo "$a : string is empty"
fi

這將產(chǎn)生以下輸出結(jié)果:

abc = efg: a is not equal to b
abc != efg : a is not equal to b
-z abc : string length is not zero
-n abc : string length is not zero
abc : string is not empty

要注意以下幾點(diǎn):

  • 運(yùn)算符和表達(dá)式之間必須有空格,例如2+2是不正確的,因?yàn)樗鼞?yīng)該寫成2 + 2.
  • if...then...else...fi 語句在下一章節(jié)中已經(jīng)解釋的決策聲明。

 




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