扣丁学堂Linux培训简述shell中常见参数及判断命令

2019-04-02 15:34:19 1718浏览

今天小编给读者们分享一下shell中常见参数及判断命令，对Linux开发技术感兴趣或者是想要参加Linux培训进入Linux开发领域中的小伙伴可以随小编来看一下，文中有详细的代码列出，具有很好的参考价值，希望对读者们有所帮助。

Shell常用特殊变量：

经常会在shell命令中，看到$0, $#, $*, $@, $?, $$这样的取值，这些代表什么呢?

$* 和 $@ 都是将参数一个一个返回

"$*"将所有参数当做一个整体字符串返回 , "$@"将参数一个一个返回

常用判断参数

在shell命令文件中还经常会看到类似与if [ -z "${SPARK_HOME}" ]; then这样的判断语句?是不是也和我一样很疑惑-z是什么含义?

下面是几个常见的参数，供查询使用：

-a file exists. 
-b file exists and is a block special file. 
-c file exists and is a character special file. 
-d file exists and is a directory. 
-e file exists (just the same as -a). 
-f file exists and is a regular file. 
-g file exists and has its setgid(2) bit set. 
-G file exists and has the same group ID as this process. 
-k file exists and has its sticky bit set. 
-L file exists and is a symbolic link. 
-n string length is not zero. 
-o Named option is set on. 
-O file exists and is owned by the user ID of this process. 
-p file exists and is a first in, first out (FIFO) special file or named pipe. 
-r file exists and is readable by the current process. 
-s file exists and has a size greater than zero. 
-S file exists and is a socket. 
-t file descriptor number fildes is open and associated with a terminal device. 
-u file exists and has its setuid(2) bit set. 
-w file exists and is writable by the current process. 
-x file exists and is executable by the current process. 
-z string length is zero. 

判断命令

shell中除了有上边这样用来判断文件是否存在的参数，当然还有判断两个数是否相等这样更常规的命令。

例如，if [ $# -gt 0 ]这样判断传入参数个数是否为0

以上就是扣丁学堂Linux在线学习小编给大家分享的shell中常见参数及判断命令，希望对小伙伴们有所帮助，想要了解更多内容的小伙伴可以登录扣丁学堂官网咨询。

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