There are several useful tests that you can make using Jinja2 builtintestsandfilers. In this article, i’ll show how to test if a variable exists or not, if it is empty or not and if it is set to True. I’ll also give two examples of how to combine these checks. Check Variable ...
2. Using a non-empty check 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...
Afterdeclaring a string variable, use the-zoperator in anif statementto check whether a string is empty or not: MY_STRING="" if [ -z $MYSTRING ] then echo "String is empty" else echo "String is not empty" fi For more Shell scripting tips,check out or Bash/Shell scripting articles!
在这个例子中,使用了-z选项来判断字符串$str是否为空。如果字符串为空,则输出”String is empty.”,否则输出”String is not empty.”。 ## 多个条件的判断 if命令也支持多个条件的判断,可以使用逻辑运算符将多个条件连接起来。 下面的示例展示了如何使用if命令来判断一个数字是否大于10并且小于20: “`shell #...
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-ErrorAction:SilentlyContinue parameter is not being respected & $error variable not updated -ExpandProperty & Export CSV !!! powershell script to add a word in the beginning of the text file - URGENT !!! 'A positional parameter cannot be found that accepts argument '$null'. 'Name' Attribut...
to checkfora variable being emptyinshell iswith`-z`# you can have problemswithtestsinsome shell...
LinuxShell_variable+if+while [root@ossec-server mybash]# vim ./hello.sh #! /bin/sh # Thisisa example bash script echo"Hello world! \n"echo"parameter num: $#"echo"script's name is $0"echo"parameter 0: $1"echo"parameter 1: $2"if[ $# -ge1] # 注意:方括号[]内的描述内容前后...
if [ -z "$var" ]; then echo "Variable is empty"; else echo "Variable is not empty"; fiCheck if a variable is empty 1. Using if-else to check whether two numbers are equal When trying to understand the working of a function like if-else in a shell script, it is good to start...
In PowerShell, checking if a variable is null (or in PowerShell terms, $null) is a fundamental task in scripting, especially when dealing with the output of commands, function returns, or processing user input. For instance, a variable storing data from database might be null if no data ...