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扣丁學堂Linux培訓簡述shell中常見參數(shù)及判斷命令

2019-04-02 15:34:19 2959瀏覽

今天小編給讀者們分享一下shell中常見參數(shù)及判斷命令，對Linux開發(fā)技術感興趣或者是想要參加Linux培訓進入Linux開發(fā)領域中的小伙伴可以隨小編來看一下，文中有詳細的代碼列出，具有很好的參考價值，希望對讀者們有所幫助。

Shell常用特殊變量：

經(jīng)常會在shell命令中，看到$0, $#, $*, $@, $?, $$這樣的取值，這些代表什么呢?

$* 和 $@ 都是將參數(shù)一個一個返回

"$*"將所有參數(shù)當做一個整體字符串返回 , "$@"將參數(shù)一個一個返回

常用判斷參數(shù)

在shell命令文件中還經(jīng)常會看到類似與if [ -z "${SPARK_HOME}" ]; then這樣的判斷語句?是不是也和我一樣很疑惑-z是什么含義?

下面是幾個常見的參數(shù)，供查詢使用：

-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. 

判斷命令

shell中除了有上邊這樣用來判斷文件是否存在的參數(shù)，當然還有判斷兩個數(shù)是否相等這樣更常規(guī)的命令。

例如，if [ $# -gt 0 ]這樣判斷傳入?yún)?shù)個數(shù)是否為0

以上就是扣丁學堂Linux在線學習小編給大家分享的shell中常見參數(shù)及判斷命令，希望對小伙伴們有所幫助，想要了解更多內容的小伙伴可以登錄扣丁學堂官網(wǎng)咨詢。

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