In this method, I will be using the-nflag to check whether the variable is empty or not. Here's the simple script which will tell me whether the variable is empty or non-empty: #!/bin/bash variable="" if [ -n "$variable" ]; then echo "Variable is not empty." else echo "Vari...
Afterdeclaring a string variable, use the-zoperator in anif statementto check whether a string is empty or not: MY_STRING="" if [ -z $MYSTRING ] then echo "String is empty" else echo "String is not empty" fi For more Shell scripting tips,check out or Bash/Shell scripting articles!
When working with shell scripts, it’s important to be able to check if a file exists and if it’s empty or not. This is especially useful when automating tasks that rely on specific files being present and non-empty, here is an example that illustrate how to check if the file exists ...
请参阅 Bash 手册中的 Shell 参数扩展 和模式匹配 。 2投票 [ $(echo $variable_to_test | sed s/\n// | sed s/\ //) == "" ] && echo "String is empty" 从字符串中删除所有换行符和空格将导致空白字符串被减少为可以测试和操作的空白 最新...
read [-options] [variable...] 上面语法中,options是参数选项,variable是用来保存输入数值的一个或多个变量名。如果没有提供变量名,环境变量REPLY会包含用户输入的一整行数据。 下面是一个例子demo.sh。 #!/bin/bash echo -n "输入一些文本 > "
bash 中的条件语句，基础就是 Test 。 if 先来个实例： x=5; if [ $x = 5 ]; then e...
How To Check Existence of Input Argument in a Bash Shell Script There are three different ways: Using the “test” command Using the “$#” variable Using the “-n” option Method 1: Using the “test” Command The “test” command, also known as the “[” command, is a built-in co...
Use the if-else statement with the -v option to check if an environment variable is set in bash. The echo command in the if block will be executed if the will
一旦一個變數被定義了,它只能用內建命令 unset 來取 消(參見下面 shell 內建命令(SHELL BUILTIN COMMANDS) 章節). 一個變數 variable 可以用這樣的語句形式來賦值: name=[value] 如果沒有給出值 value, 變數就被賦為空字串。所有值 values 都經過了波浪線擴充套件,引數和變數擴充套件,命令 替換,算術擴充...
Check to see if a variable is empty or not Create a new bash file, named, and enter the script below. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not em...