STRING True if string is not empty. 即,test命令使用-z STRING操作符来判断STRING字符串的长度是否为 0。 如果为 0,就是空字符串,会返回 true。 具体写法是test -z STRING,使用[命令则写为[ -z STRING ]。 -n STRING操作符判断STRING字符串的长度是否为 0。 如果不为
Here is another option, “-n”, to check whether the specified string is empty or not. It works on the rule of checking the length of a string by counting the string characters in it. If the length of a particular string turns out to be other than zero, it will return “true”; o...
Bash技巧:对比 test判断字符串是否为空的用法,#!/bin/bashfunctionempty_string(){iftest-n$1;thenecho'(1)-n$1:'"Noquote:notempty."fiif[-z$1];thenecho'(2)-z$1:'"Noquote
if [[ -z $string ]]; then echo "The string is empty." else echo "The string is not empty." fi 这是我们执行脚本时的结果: 代码语言:txt AI代码解释 $ ./test.sh Strings are different. 例4 -n运算符还可用于测试字符串长度是否不为零。 代码语言:txt AI代码解释 #!/bin/bash string="hel...
‘STRING’ 将会阻止 STRING 中所有特殊字符的解释,这是一种比使用"更强烈的形式。后面的实验会详细说明。 反引号(`) 命令替换 反引号中的命令会优先执行,如: cp `mkdir back` test.sh back ls 先创建了 back 目录,然后复制 test.sh 到 back 目录。
iftest"$abc";thenecho"It's not an empty string."elseecho"It's an empty string."fi 运行上面代码的输出结果为: It's an empty string. 这是因为我们没有定义变量 abc ,所以 "$abc" 被解释成了空字符串。 其实使用检查空字符串的运算符 -n 会让代码具有更清晰的含义: ...
The-zoperator on the other is used to test whether a string is empty. Now, let's combine both of these and write a simple bash script: #!/bin/bash array1=('1' '23' '4' '56' '78' '9' '0') array2=() if [[ -z "${array1[@]}" ]]; then ...
In this example, the substitution command is used with $() to capture the output of grep, and then the -z option of the test command is used to check if the resulting string is empty or not. Here, the grep command searches for the pattern pattern in the file dummy.txt. The output...
-n is one of the supported bash string comparison operators used for checking null strings in a bash script. When -n operator is used, it returns true for every case, but that’s if the string contains characters. On the other hand, if the string is empty, it won’t return true. ...
-z string:测试指定字符串是否为空,空则真,不空则假 -n string:测试指定字符串是否不空,不空为真,空则为假 4、组合测试条件 -a:与关系 -o:或关系 !: 非关系 if [ $# -gt 1 -a $# -le 3 ] if [ $# -gt 1 ] && [ $# -le 3 ] ...