Although[[ 1 == 1 ]]and[[ $(( 1+1 )) == 2 ]]can be executed, it should be noted that they test for string equality instead of arithmetic equality. Assuming-eqis executed, it is likely that1+1will be equal to2, despite2being a string with an additional space at the end. $ ...
使用双中括号 [[:[[ "string1" operator "string2" ]],这种方法提供了更多的功能和灵活性。 3. 给出bash中字符串对比的具体示例 示例1:检查两个字符串是否相等 bash string1="hello" string2="hello" if [ "$string1" = "$string2" ]; then echo "The strings are equal." else echo "The strin...
这些比较操作符的函数语法是,一个操作符加一个或两个参数放在中括号内,后面跟一系列程序语句,如果条件为真,程序语句执行,可能会有另一个程序语句列表,该列表在条件为假时执行: if [ arg1 operator arg2 ] ; then list 或 if [ arg1 operator arg2 ] ; then list ; else list ; fi 像例子中那样,在比...
='operators are used, thestringto the right of the operator is used as a pattern and pattern matching is performed. When the `=~'operator is used, the string to the right of the operatoris matched as a regular expression. The&& and || operatorsdonot evaluate EXPR2ifEXPR1 is sufficient...
某个变量为空时,会报错:-bash: [: ==: unary operator expected 解决办法 []改为 [[ ]] if [[ $2 == '' ]]; then 但是 这种方式 有时会出现无法判读的错误 , if [ $2 -eq '' ]; then 才是合适的解决方式 === 1 2 3 4 if[...
Logical Operator Meaning Usage =~ Matches Regular Expression [[ $consonants =~ [aeiou] ]] = String Equal To [[ $password = "pegasus" ]] != String Not Equal To [[ $fruit != "banana" ]] ! Not [[ ! "apple" =~ ^b ]] If和Else 条件表达式的功能非常强大,因为我们可以使用它们来控制...
echo X is equal to Y fi 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Output: 条件语句(决策) 条件是求值为布尔表达式(true或false)的表达式。要检查条件,可以使用if、if-else、if- if-else和嵌套条件。 条件语句的结构如下:
[root@c7-server ~]# [ $name ==tom ]-bash: [: ==: unary operator expected 因为$name为空,因此整个表达式就变成了。 [ == tom ] 所以bash会报错并告诉你我们期待的是一元(unary)运算符(因为只有tom这个字符串)。一元也可以叫单目,是一样的意思。
igi@gentoo ~ $ if["$HOME" = "/home/igi" ];then echo 'equal'; fi bash: syntax error near unexpected token `then' 语法分析错误,很明显,if[ 对于bash来说,不知道是什么鬼东西 b. [与后面的参数之间缺少空格 igi@gentoo ~ $ if ["$HOME" = "/home/igi" ];then echo 'equal'; fi ...
If the first number is less than or equal to the second, the condition evaluates to true; otherwise, it evaluates to false. The-leoperator is commonly used in conditional statements likeifandwhile. Examples of-le(Less Than or Equal To) Operator ...