echo "The Boolean is true." else echo "The Boolean is false." fi OUTPUT 1 2 3 The Boolean is false. Use if with [[ ]] Command Use the if statement with the [[ ]] command to check if boolean is true in Bash. Use if with Double Square Brackets 1 2 3 4 5 6 7 8 boo...
使用read命令读取输入的行内容,并判断是否为空。示例代码如下: 代码语言:bash 复制 read line if [ -z "$line" ]; then echo "该行为空" else echo "该行不为空" fi 这两种方法都使用了-z选项来判断变量是否为空。如果为空,则返回true,否则返回false。 应用场景: 在处理文本文件时,需要判断某一行是否...
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...
它们可以以相同的方式组成：if case $HOST in node*) true;; *) false;; esac; then ...
检查文件是否存在时,最常用的FILE运算符是-e和-f。第一个将检查文件是否存在而不管类型如何,而第二个将只在FILE是常规文件(不是目录或设备)时返回true。 检查文件是否存在时,最可读的选项是将test命令与if语句结合使用。下面的任何片段都会检查/etc/resolv.conf文件是否存在: ...
[[ -f"$File"]] &&echo"true" We can couple it with the Bash if statement to develop conditions. It is usually employed for conditional branching and caters to numerical or string comparisons. However, we can determine the status of a file as well. This check is widely used to redirect ...
File CheckReturnsDescription -bTrue文件是否为块文件。-cTrue文件是否为特殊字符文件。-dTrue文件是否为...
f()if true; then echo "$1"; fi f()for i in "$@"; do echo "$i"; done if语法更短 # One line # Note: The 3rd statement may run when the 1st is true [[ $var == hello ]] && echo hi || echo bye [[ $var == hello ]] && { echo hi; echo there; } || echo bye ...
重要地记住 then 和 fi 在shell里面被认为是分开的语句。因此,在命令行上使用的时候,他们用分号隔开。 在脚本中,if语句的不同部分通常是良好分隔的。以下是一些简单的例子: 7.1.1.3. 检查文件 第一个例子检查一个文件是否存在: anny ~> cat msgcheck.sh #!/bin/bash echo "This scripts checks the ...
Check if a File Does not Exist Testing for a file returns0(true) if the file exists and1(false) if it does not exist. For some operations, you may want to reverse the logic. It is helpful to write a script to create a particular file only if it doesn’t already exist. ...