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...
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 0,就不是空字符串,会返回 true。
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$1:'"Noquote
iftest -z"$abc";thenecho"It's an empty string."fi 这段代码输出的结果仍然是: It's an empty string. 判断字符串相等 test 支持两个运算符来判断字符串相等:= 和 ==。 abc="hello"iftest"hello"=="$abc";thenecho"You got same string."fi 运行上面代码的输出结果为: You got samestring. 因...
‘STRING’ 将会阻止 STRING 中所有特殊字符的解释,这是一种比使用"更强烈的形式。后面的实验会详细说明。 反引号(`) 命令替换 反引号中的命令会优先执行,如: cp `mkdir back` test.sh back ls 先创建了 back 目录,然后复制 test.sh 到 back 目录。
string "0" is false } else { echo "string \"0\" is not false \r\n"; } 空数组...false \r\n"; } else { echo "string \"0.0\" is not false \r\n"; // 输出:string "0.0" is not false } 正确地检查一个变量是否为空应该使用...php if (empty($var)) { ... } 原文链接:...
string="" 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。
The uses of the “-z” and “-n” option to test the string values using the “if” statement in Bash are shown in this tutorial. Using the “If -Z” Statement Sometimes, it is required to check if a string variable is empty or if it contains a string of zero length. There are...
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...