脚本语言Bash简明教程（完结篇）

Posted 2022-12-19 白马负金羁

Bash（GNU Bourne-Again Shell）is a Unix shell and script language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. First released in 1989, it has been used as the default login shell for most Linux distributions.
 

一、条件语句与分支结构

1. If-Else结构的三种基本语法

语法1

if [ condition ] ; then
else
fi

语法2

if [ condition ] ; then
elif [ condition ]; then
else
fi

语法3（嵌套）

if [ condition ] ; then
    if [ condition ] ; then
    else
    fi
else
fi

其中，的Conditional Statement 可以分三种情况讨论。

1.1 字符串比较操作

操作符	描述
-z string	如果string的长度是0，则True
-n string