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,$vari...
if[!-z"$variable"];thenecho"Variable is not empty"elseecho"Variable is empty"fi 在这个示例中,$variable是要检查的变量。如果它不为空,则打印"Variable is not empty";否则,打印"Variable is empty"。 使用条件表达式检查变量是否为空 除了if 语句,还可以使用条件表达式来检查变量是否为空。条件表达式可以...
First, use the following command to create and open an empty file: nano length.sh Now, paste the following lines of code into the file: #!/bin/bash # Set the variable variable="" # Check if the variable is empty if [ -z "$variable" ]; then echo "Variable is empty." else echo...
Bash has a few conditional expressions, of which you can use one to check if a variable is empty or not. That is the-zoperator. Using the-zoperator followed by a variable will result in trueif the variable is empty. The condition will evaluate to false if the variable is not empty. ...
Checking If Variable Is Empty in Bash There are multiple ways to check if a variable is empty or not. Before moving towards those methods, knowing when a variable is called empty is necessary. In Bash, a variable is called empty if: A variable is declared without assigning any value to ...
常见$(variable) 3 初始化数组 array=(a b c d) 接下来是一个demo,内含详细注释 #!/bin/bash # 单方括号内可以使用变量 SWAP_DEVICE=/dev/sda1 if [ ${SWAP_DEVICE} == "/dev/sda1" ]; then echo "单方括号内可以使用变量" fi # 双方括号内可以使用变量 ...
x="Non-empty variable" if [[ "$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" fi...
- Test if a given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number: [[ $variable -eq|ne|gt|lt|ge|le integer ]] - Test if the specified variable has a [n]on-empty value:...
TestFile1 does not exist or is empty. 向文件添加一些内容,然后再测试一次: [student@studentvm1 testdir]$ File="TestFile1" ; echo "This is file $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; else echo "$File does not exist or is empty." ...
- Testifa given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number: [[$variable-eq|ne|gt|lt|ge|leinteger]] - Testifthe specified variable has a [n]on-empty value: ...