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
Checks if a String is not empty ("") and not null. StringUtils.isNotEmpty(null) = false StringUtils.isNotEmpty("") = false StringUtils.isNotEmpty(" ") = true StringUtils.isNotEmpty("bob") = true StringUtils.isNotEmpty(" bob ") = true Parameters: str - the String to check, may ...
-z is the second supported bash string comparison operator used to check if a string is empty or not. The -z operator functions similarly like -n operator. Below is an example: Most importantly, you should add spaces around the square brackets. If there are no spaces, bash will complain ...
function yesNo { # Prompts user with $1, returns true if response starts with y or Y or is empty string read -e -p " $1 [Y/n] " YN [[ "$YN" == y* || "$YN" == Y* || "$YN" == "" ]] } Use it like this: $ if yesNo "asfd"; then echo "true"; els...
myArray is NOT empty and contain 3 elements How to check if a Bash Array contains a value? There is no in array operator in bash to check if an array contains a value. Instead, to check if a bash array contains a value you will need to test the values in the array by using a...
代码语言:txt 复制 str="" if [ "$str" == "" ]; then echo "String is empty" else echo "String is not empty" fi 字符串长度比较:可以使用大于号(>)、小于号(<)来比较两个字符串的长度。例如: 代码语言:txt 复制 str1="Hello" str2="World" if [ ${#str1} -gt ${#str2} ]; the...
# empty string rval="" return fi # wc puts some space behind the output this is why we need sed: numofchar=`echo -n "$1" | wc -c | sed 's/ //g' ` if [ "$numofchar" = "1" ]; then # only one char in string
如果if结构使用的不是test命令,而是普通命令,比如上一节的((...))算术运算,或者test命令与普通命令混用,那么可以使用 Bash 的命令控制操作符&&(AND)和||(OR),进行多个命令的逻辑运算。$ command1 && command2 $ command1 || command2对于&&操作符,先执行command1,只有command1执行成功后, 才会执行command2。
The firstjqargument is'""'which outputs an empty string, effectively preventingjqfrom making any processing of the JSON for printing <<<followed by a string is called a "Here String", and is basically telling bash to treat the string as if it was a file and pass it toSTDIN(As input ...
- Test if the specified variable has a [n]on-empty value: [[ -n $variable ]] - 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: ...