You can assign data to a variable using the equals sign (=). The data you store in a variable can either be a string or a number. Let’s create a variable now on the command line: chapter_number=5 The variable name is on the left hand side of the equals sign, and the data whic...
[student@studentvm1 testdir]$ MyVar="Random text" ; if [ -z "" ] ; then echo "MyVar is zero length." ; else echo "MyVar contains data" ; fi MyVar is zero length. 你也可以这样做: [student@studentvm1 testdir]$ MyVar="Random text" ; if [ -n "$MyVar" ] ; then echo "MyVar...
MyVar is zero length. 你也可以这样做: [student@studentvm1 testdir]$ MyVar="Random text" ; if [ -n "$MyVar" ] ; then echo "MyVar contains data." ; else echo "MyVar is zero length" ; fi MyVar contains data. [student@studentvm1 testdir]$ MyVar="" ; if [ -n "$MyVar" ] ; ...
How to do string comparison and check if a string equals to a value? How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with...
X equals 1 [student@studentvm1 testdir]$ X=0 ; if [ $X -eq 1 ] ; then echo "X equals 1" ; else echo "X does not equal 1" ; fi X does not equal 1 [student@studentvm1 testdir]$ 自己来多尝试一下其他的。 杂项操作符 ...
Bash 简介 转自 https://wangdoc.com/bash/intro.html Bash 是 Unix 系统和 Linux 系统的一种 Shell(命令行环境),是目前绝大多数 Linux 发行版的默认 Shell。 目录 [隐藏] 简介 基本语法 模式扩展 引号和转义 变量 字符串操
The line read is saved in the variable REPLY. The list is executed after each selection until a break command is executed. The exit status of select is the exit status of the last command executed in list, or zero if no commands were executed....
如果if结构使用的不是test命令,而是普通命令,比如上一节的((...))算术运算,或者test命令与普通命令混用,那么可以使用 Bash 的命令控制操作符&&(AND)和||(OR),进行多个命令的逻辑运算。$ command1 && command2 $ command1 || command2对于&&操作符,先执行command1,只有command1执行成功后, 才会执行command2。
In bash shell, when you use a dollar sign followed by a variable name, shell expands the variable with its value. This feature of shell is called parameter expansion. But parameter expansion has numerous other forms which allow you to expand a parameter and modify the value or substitute othe...
[student@studentvm1 testdir]$File="TestFile1";touch$File;if[-s $File];thenecho"$File exists and contains data.";elseecho"$File does not exist or is empty.";fi TestFile1doesnotexistorisempty. 1. 2. 向文件添加一些内容,然后再测试一次: ...