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。
then declare a variable named "val" with a string value of "Aqsa". Inside the "if" statement, set a condition to check if the string value of variable $val is not equal to "Aqsa". If this condition is met, the first echo statement...
The number1 should be less or equal to the number2 and it gave me the same output when I executed the above script: 5. The -gt (greater than) operator The -gt operator is used to compare two values and find out if the first variable is greater than the second one. Here's how ...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
Line 7performs a check using anifstatement. When the variable equals two ("$i" == 2), the program exits thewhileloop using the Bashbreakstatement online 10. In that case, the code jumps toline 16. If the variable is a different number, the script continues as expected online 12. ...
In this case, the expression is slightly different, instead of typing true or false, thestdoutvariable is printed using$?. Check if strings are not equals The!=operator checks if String1 is not equal to String2. If the two strings are not equal, then it returns 0. If two strings are...
-z foo - Check if variable exists String Operators = - Equals == - Equals -z - Is null -n - Is not null < - Is less than in ASCII alphabetical order > - Is greater than in ASCII alphabetical order If Statements #!/bin/bash if [[$foo = 'bar']]; then echo 'one' elif [[...
图1-1 。GNU emacs文本编辑器中的 Shell 代码 注意在Windows 文本文件中,!“行以两个字符结束:一个回车符 (CR)和一个换行符 (LF)。在 Unix 系统上,比如 Linux,行以一个换行符结束。如果在 Windows 文本编辑器中编写程序,则必须用 Unix 行尾保存文件,或者在保存后删除回车。 建设一个更好的“你好,世界!
Then, the script will create a new variable named myvariablename. Mind that in order to assign a new variable, you will need to use an equals sign (=). We will use the echo command to print out the variable value. We also need to use a dollar sign ($), so the bash knows we ...
JAVA interface类有且仅有1个公共抽象方法有@FunctionalFunction标注(可选)比如我们在多线程场景中都很熟悉的Runnable接口,就是个典型的函数式接口,符合上面说的2个特性..., T o2); boolean equals(Object obj); // 其他方法省略... } 可以看到,Comparator接口里面提供了 compare和 equals两个抽象方法...那按照...