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...
在bash中,我们可以使用if语句结合条件判断来判断一个变量是否为空。具体的语法如下: ```bash if [ -z "$var" ]; then echo "Variable is empty" else echo "Variable is not empty" fi ``` 在上面的示例中,-z表示判断变量是否为空,$var是我们要判断的变量。如果变量var为空,则输出“Variable is empty...
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...
Check to see if a variable is empty or not Create a new bash file, named, and enter the script below. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not em...
VARIABLE=value # 脚本将会尝试运行"value"命令,同时设置环境变量"VARIABLE"为""。 上面$b和$c的区别? 实际应用的角度来说,基本没区别,都是空值。技术的角度加以区别的话,如下: 代码语言:javascript 复制 ```bash if [ -z "$b" -a "${bxxx}" = "xxx" ] # 这里的判断会有单独的文章介绍...
echo "The string is not empty" fi Output: The string is empty Explanation: In the exercise above, The variable 'input_str' is defined as an empty string. An if statement checks if the length of '$input_str' is zero using the -z test operator. ...
TestFile1 does not exist or is empty. 向文件添加一些内容,然后再测试一次: [student@studentvm1 testdir]$ File="TestFile1" ; echo "This is file $File" > $File ; if [ -s $File ] ; then echo "$File exists and contains data." ; else echo "$File does not exist or is empty." ...
- Testifthe specified variable has an empty value: [[ -z$variable]] - Testifthe specified [f]ile exists: [[ -f path/to/file ]] - Testifthe specified [d]irectory exists: [[ -d path/to/directory ]] - Testifthe specified file or directory [e]xists: ...
- Test if the specified variable has an empty value: [[ -z $variable ]] - Test if the specified [f]ile exists: [[ -f path/to/file ]] - Test if the specified [d]irectory exists: [[ -d path/to/directory ]] - Test if the specified file or directory [e]xists: ...
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.