x="Non-empty variable"if[["$x"==""]];thenecho"x is empty"elseecho"x is not empty"fi 检查Bash 中的变量是否为空 - 使用替换方法检查 如果定义了x,则表达式被替换为test,否则为null。 if[${x:+test}];thenecho"x is not empty"elseecho"x is empty"fi...
在上述代码中,首先定义了一个变量my_variable并赋值为"Hello World"。然后使用条件语句if来检查变量值是否为空,如果为空则输出"变量值为空",否则输出变量的值。接着使用条件语句if来检查变量值是否等于"Hello World",如果等于则输出"变量值等于 'Hello World'",否则输出"变量值不等于 'Hello World'"。 Bash的检...
If yes, then print the value. If no, then use the default value “Greenland”. Basically, we’re setting a default value that will be used when the variable is not set or have a null value. Method 3 – Assigning default value to empty variable This section will showcase how to assig...
复制 if[-v variable];then echo"variable is set"elseecho"variable is not set"fi
is a ! or a ^ then any character not enclosed is matched. The sorting order of characters in range expressions is determined by the current locale and the value of the LC_COLLATE shell variable, if set. A - may be matched by including it as the first or last character in the set. ...
http://blog.51cto.com/64314491/1629219---bash条件判断之if语句(二) 一、条件测试方式: bash命令 [ expression ] 一个中括号,其中内容为命令,括号两端必须要有空格 [[ expression ]] 两个中括号,其中内容为关键字,括号两端必须要有空格 test expression...
location"# Notice that the space in the $location variable is ignored and the location argument accepts the entire string as the value In the JSON dictionary output, review the properties of the resource group that was created. Using If Then Else to determine if variable is null...
location"# Notice that the space in the $location variable is ignored and the location argument accepts the entire string as the value 在JSON 字典输出中,查看已创建资源组的属性。 使用If Then Else 确定变量是否为 NULL 若要评估字符串,请使用!=;若要评估数字,请使用-ne。 以下 If Then Else 语句...
-s "myvariable" ]; then echo -e "variable is null!" ; fi #True of the length if "STRING" is zero. # Using test command (same as []), to test if the length of variable is nonzero test -n "$myvariable" && echo myvariable is "$myvariable" || echo myvariable is not set ...
if语法[Linux(bash_shell)] http://blog.csdn.net/ycl810921/article/details/4988778 1: 定义变量时, =号的两边不可以留空格. eg: gender=femal---right gender =femal---wrong gender= femal---wrong 2 条件测试语句 [ 符号的两边都要留空格.