if[ ! -z"$variable"];thenecho"Variable is not empty"elseecho"Variable is empty"fi 在这个示例中,$variable是要检查的变量。如果它不为空,则打印"Variable is not empty";否则,打印"Variable is empty"。 使用条件表达式检查变量是否为空 除了if 语句,还可以使用条件表达式来检查变量是否为空。条件表达式可...
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 "$variable" ]; then echo "Variable is...
x="Non-empty variable"if[["$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[${x:+test}];thenecho"x is not empty"elseecho"x is empty"fi...
Basically, we’re setting a default value that will be used when the variable is not set or have anullvalue. Method 3 – Assigning default value to empty variable This section will showcase how to assign the default value to a variable if the variable is empty. The command structure is ...
x="Non-empty variable" if [[ "$x" == "" ]]; then echo "x is empty" else echo "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} ]; then echo "x is not empty" else echo "x is empty...
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!
empty string variable “val” first. After this, we have been using the “-n” option within the “if” part of the “if-else” statement within the square brackets. This option is checking whether the length of variable “val” is other than zero or not. If the length of variable ...
1.变量通过“ ”引号引起来 如下所示，可以得到结果为 is null #!/bin/bash para1= if[!
BASH IF http://lhsblog01.blog.163.com/blog/static/10200451920081118105937818/ Linux SHELL if 命令参数说明 2007年10月30日 星期二 08:47 *–b 当file存在并且是块文件时返回真 * -c 当file存在并且是字符文件时返回真 * -d 当pathname存在并且是一个目录时返回真 ...
Then, the if statement checks if the $count variable is zero. If the $count variable is zero, the grep output was empty, passed to the wc-1 because the pattern was not matched. The script then outputs the message No match found. to the console using the echo command. That’s all ab...