Bash 入門 學習筆記

1. $ myvar='This is my environment variable!'

輸出

1. $ echo $myvar
2. This is my environment variable!

分割

1. $ echo foo${myvar}bar
2. fooThis is my environment variable!bar

寫個c程序交互一下，用c語言來讀取環境變量~~

1. #include <stdio.h>
2. #include <stdlib.h>
4. int main(void) {
5. char *myenvvar=getenv("EDITOR");
6. printf("The editor environment variable is set to %s\n",myenvvar);
7. }

沒給EDITOR幅值，當然就不會顯示啦~~

1. $ ./myenv
2. The editor environment variable is set to (null)

賦值了啊。。為啥還不顯示呢？？

1. $ EDITOR=xemacs
2. $ ./myenv
3. The editor environment variable is set to (null)

原來要export一下，哈哈，這下出來了

1. $ export EDITOR
2. $ ./myenv
3. The editor environment variable is set to xemacs

這裡要注意，unset之後，就算再export，那個變量也沒掉的了。需要重新幅值

1. $ unset EDITOR
2. $ ./myenv
3. The editor environment variable is set to (null)

1、賦值，EDITOR="vim"，注意"="旁邊不能有空格啊~

2、調用，$EDITOR 或者 ${EDITOR}

3、export EDITOR

4、unset EDITOR

5、c語言調用函數，char *envname = getenv("EDITOR");