Check Empty Variable Linux Bash

You can determine if a variable is empty in Linux using the following methods:

1. Check if the variable is empty using an if statement.

if [ -z "$var" ]; then
    echo "变量 var 为空"
else
    echo "变量 var 不为空"
fi

1. Check if a variable is empty using the test command.

if test -z "$var"; then
    echo "变量 var 为空"
else
    echo "变量 var 不为空"
fi

The -z option is used to test if a variable is empty. It returns true if the variable is empty, otherwise it returns false.

Alternatively, you can also use the following simplified method for evaluation:

[ -z "$var" ] && echo "变量 var 为空" || echo "变量 var 不为空"

Alternatively:

test -z "$var" && echo "变量 var 为空" || echo "变量 var 不为空"