在这个示例中,$variable是要检查的变量。如果它为空,则打印"Variable is empty";否则,打印"Variable is not empty"。 使用双引号和等号 另一种常见的方法是使用双引号和等号进行比较。 以下是示例代码: if["$variable"=""];thenecho"Variable is empty"elseecho"Variable is not empty"fi 在这个示例中,$vari...
在这个示例中,$variable是要检查的变量。如果它为空,则打印"Variable is empty";否则,打印"Variable is not empty"。 使用双引号和等号 另一种常见的方法是使用双引号和等号进行比较。 以下是示例代码: if["$variable"=""];thenecho"Variable is empty"elseecho"Variable is not empty"fi 在这个示例中,$vari...
In this method, I will be using the-nflag to check whether the variable is empty or not. Here's the simple script which will tell me whether the variable is empty or non-empty: #!/bin/bash variable="" if [ -n "$variable" ]; then echo "Variable is not empty." else echo "Vari...
function empty { local var="$1" # Return true if: # 1. var is a null string ("" as empty string) # 2. a non set variable is passed # 3. a declared variable or array but without a value is passed # 4. an empty array is passed if test -z"$var" then [[ $( echo"1" ...
echo 'NEWSTR="WORLD"' >> test.sh echo 'echo "NEWSTR is $NEWSTR"' >> test.sh bash test.sh #hello world PID:25318 ParentPID:19245 #STR is #NEWSTR is WORLDecho $NEWSTR #this will give empty output #. test.sh #hello world PID:19245 ParentPID:19243 #STR is HELLO #NEWSTR is ...
echo 'b is set but empty'; # 设置但为空 else echo 'b is not set'; # 没设置,如 c fi``` 变量中的空格 代码语言:javascript 代码运行次数:0 运行 AI代码解释 e=123# 报错,变量中间当然不能有空格 e='1 2 3';f='1 2 3';echo $e;#123echo $f;#?echo"$f";#?
Bash 简介 转自 https://wangdoc.com/bash/intro.html Bash 是 Unix 系统和 Linux 系统的一种 Shell(命令行环境),是目前绝大多数 Linux 发行版的默认 Shell。 目录 [隐藏] 简介 基本语法 模式扩展 引号和转义 变量 字符串操
The-zoperator returnstrueif a string variable is null or empty. How the use the-zBash Operator Afterdeclaring a string variable, use the-zoperator in anif statementto check whether a string is empty or not: MY_STRING="" if [ -z $MYSTRING ] ...
#"This""is""a""variable""containing""five""words"COMMAND"This is $variable1"# 用下面1个参数执行COMMAND命令: #"This is a variable containing five words"variable2=""# Empty. COMMAND $variable2 $variable2 $variable2 # COMMAND将不带参数执行. ...
#Check the variable is set or unset if[$checkval-eq“World”];then echo"‘str’ variable is set and the value is$str" else echo"‘str’ variable is not set" fi Run the script. $bashcheckvar2.sh Example-3: Check the variable is empty or not ...