或:bash conditional-statements logical-operators 1个回答 51投票 if [[ ! ($var == 2 || $var == 30 || $var == 50) ]] ; then do something fi 一个好的做法是在您的条件操作员和操作数之间拥有空间。 也可能建议,如果您只是比较数字,改用算术运算符,或者只是使用(( ))
Pay special attention to space. There must be space between the opening and closing brackets and the conditions. Similarly, space must be before and after the conditional operators (-le, == etc). Here's what it shows when I run the script: Did you notice that the script tells you when ...
Unary operators are often used to test the status of a file, a variable, a shell option (optname), or a string. Unary and Binary expressions are formed with the following primaries. Conditional ExpressionMeaning -a file True if file exists....
Conditional statements are a fundamental part of any programming language, and bash scripting is no exception. They allow your scripts to make decisions based on certain conditions. The basic conditional statements in bash are ‘if’, ‘else’, and ‘elif’ (else if). Here’s a basic ‘if’...
Knowing how conditionals work in bash open up a world of scripting possibilities. We’ll learn the basic syntax, including if, else, and elif. Then we'll look at a few of the "primary" operators you can leverage in a conditional statement such as = for string equality, -eq for numeric...
There must be space before and after the conditional operator (=, ==, <= etc). Otherwise, you'll see an error like "unary operator expected". Now, let's create an example scriptroot.sh.This script will echo the statement “you are root” only if you run the script as the root use...
It is also possible to check if multiple files exist using theif conditional statements. Follow the steps below to create a script and verify the existence of multiple files simultaneously: 1. Create a new Bash script using your preferred text editor: ...
Under Logical operators, Bash provides logical OR operator that performs boolean OR operation. Bash boolean OR operator takes two operands and returns true if any of the operands is true, else it returns false. OR logical operator combines two or more simple or compound conditions and forms a ...
filename expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution, process substitution, and quote removal are performed. Conditional operators such as ‘-f’ must be unquoted to be recognized as ...
Conditional operators such as -f must be unquoted to be recognized as primaries. ==, !=, =~ 右边的字符串如被引用则进行字符串匹配,而不再是pattern match或正则匹配 ps: 可用 type 查看是否为保留字,内建命令等 2.3 Parameters (参数) A parameter is an entity that stores values. A variable is...