#!/bin/bash # Set the variable variable="" # Check if the variable is empty if [ -z "$variable" ]; then echo "Variable is empty." else echo "Variable is not empty." fi Copy Save changes and exit from the nano t
Variable is set: /root The -v option returns true if the given variable is set to an empty string, while it returns false if the provided variable is not declared. Use the if-else statement with the -z option to check if the length of the environment variable is 0 in bash. Length ...
Example-2: Check the variable is set or unset using parameter substitute Create a bash file named “check_var2.sh” and add the following script. Here, a string value is assigned to the variable, $str before checking the variable is set or unset. The ‘if’ condition will return true a...
In programming, it is essential to check if a variable is “set” or “not set,” which means you have to check if a bash script variable has a value or not. This check helps for effective data validation. However, there’s no built-in function for checking empty variables in bash sc...
- Test if a given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number: [[ $variable -eq|ne|gt|lt|ge|le integer ]] - Test if the specified variable has a [n]on-empty value:...
# 在变量内部进行字符串代换echo ${Variable/Some/A}# 会把 Variable 中首次出现的 "some" 替换成 “A”。# 变量的截取Length=7echo ${Variable:0:Length}# 这样会仅返回变量值的前7个字符# 变量的默认值echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"}# 对 null (Foo=) 和空串 (Foo="") 起作用...
$ unset x $ showvar $x is not set $ x=3 $ showvar $x is not set $ export x $ showvar $x = 3 $ x= ## in bash, reassignment doesn't remove a variable from the environment $ showvar $x is set but empty 注意 showvar不是一个 bash 命令,而是一个如清单 5-1 所示的脚本,...
How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with the Regular Expression Operator =~?
Host is reachable on port 443.In this bash script, the ncat command is used to check if the host "google.com" is reachable at the given port 443 or not. In bash, the ncat is used to establish the network’s connections and manipulation. The echo -n is used to generate an empty ou...
/bin/bash # declare STRING variable STRING="Hello World" #print variable on a screen echo $STRING Navigate to a directory where your hello_world.sh is located and make the file executable: $ chmod +x hello_world.sh Now you are ready to execute your first bash script:...