shell的关系

凌乱爱石头 ·2021-09-18 ·2 次阅读

    段落引用shell的关系最终目的是为了操作内核（kernel），
    #vim hellworld.sh 编写脚本

> (#! /bin/bash

> echo 'Hell world'

)

#ll                         查看

total 8

-rw-------. 1 root root 1259 Feb 13  2021 anaconda-ks.cfg

-rw-r--r--. 1 root root   32 Sep 18 02:46 hellworld.sh

#chmod ug+x hellworld.sh

  #ll

>total 8

>-rw-------. 1 root root 1259 Feb 13  2021 anaconda-ks.cfg

-rwxr-xr--. 1 root root   32 Sep 18 02:46 hellworld.sh

 

>#cp hellworld.sh hi.sh

#ll

total 12

-rw-------. 1 root root 1259 Feb 13  2021 anaconda-ks.cfg

-rwxr-xr--. 1 root root   32 Sep 18 02:46 hellworld.sh

-rwxr-xr--. 1 root root   32 Sep 18 02:53 hi.sh

> #chmod ug-x hi.sh

#ll

total 12

-rw-------. 1 root root 1259 Feb 13  2021 anaconda-ks.cfg

-rwxr-xr--. 1 root root   32 Sep 18 02:46 hellworld.sh

-rw-r--r--. 1 root root   32 Sep 18 02:53 hi.sh

vi hi.sh

(

#! /bin/bash

echo 'Hi world'

~

)

>#ll

total 12

-rw-------. 1 root root 1259 Feb 13  2021 anaconda-ks.cfg

-rwxr-xr--. 1 root root   32 Sep 18 02:46 hellworld.sh

-rw-r--r--. 1 root root   30 Sep 18 02:54 hi.sh

#./hi.sh       没有执行权限

-bash: ./hi.sh: Permission denied

[root@localhost ~]# sh hi.sh  （确定是执行文件./不确定就sh）

Hi world

[root@localhost ~]#

source 可调用
（绝对路径,必须是可执行文件 ./hellworld.sh
（sh 普通文件脚本文件都可以 sh hellwolrd.sh
（source 两者皆可 source hellwolrd.sh
默认在当前进程执行脚本，

uname=admin 变量
echo $uname 打印变量
admin

>#! /bin/bash

 

>echo 'Hell world'

echo suname

echo $age

1)# ./hellworld.sh   3种方法，出现不同结果

Hell world

 

>2)# sh hellworld.sh

Hell world

 

>3)# source hellworld.sh

Hell world

admin

 

>修改 vim hellworld.sh

#! /bin/bash

 

>echo 'Hell world'

echo $uname

ping www.baidu.com

~

#ping www.baidu.com

#ps -ef  查看进程         绝对路径

./hellworld.sh ps -ef 查看进程

root      1877  1506  0 03:27 pts/0    00:00:00 -bash

root      1878  1877  0 03:27 pts/0    00:00:00 /bin/bash

root      1893     2  0 03:35 ?        00:00:00 [kworker/1:3]

root      1897     2  0 03:40 ?        00:00:00 [kworker/1:0]

root      1898   994  1 03:42 ?        00:00:00 sshd: root@pts/1

root      1902   994  1 03:42 ?        00:00:00 sshd: root@notty

root      1906  1902  0 03:42 ?        00:00:00 /usr/libexec/openssh/sftp-server

root      1913  1898  0 03:42 pts/1    00:00:00 -bash

root      1930  1913  0 03:42 pts/1    00:00:00 /bin/bash ./hellworld.sh

root      1931  1930  0 03:42 pts/1    00:00:00 ping www.baidu.com

root      1932  1878  0 03:43 pts/0    00:00:00 ps -ef

 

>=====================================================

sh hellworld.sh 然后ps -ef

root      1877  1506  0 03:27 pts/0    00:00:00 -bash

root      1878  1877  0 03:27 pts/0    00:00:00 /bin/bash

root      1897     2  0 03:40 ?        00:00:00 [kworker/1:0]

root      1898   994  0 03:42 ?        00:00:00 sshd: root@pts/1

root      1902   994  0 03:42 ?        00:00:00 sshd: root@notty

root      1906  1902  0 03:42 ?        00:00:00 /usr/libexec/openssh/sftp-server

root      1913  1898  0 03:42 pts/1    00:00:00 -bash

root      1933     2  0 03:45 ?        00:00:00 [kworker/1:3]

root      1934  1913  0 03:47 pts/1    00:00:00 sh hellworld.sh

root      1935  1934  0 03:47 pts/1    00:00:00 ping www.baidu.com

root      1936  1878  0 03:47 pts/0    00:00:00 ps -ef

 

>=======================================================

source hellworld.sh  ps -ef source与前两则有区别，

root      1877  1506  0 03:27 pts/0    00:00:00 -bash

root      1878  1877  0 03:27 pts/0    00:00:00 /bin/bash

root      1898   994  0 03:42 ?        00:00:01 sshd: root@pts/1

root      1902   994  0 03:42 ?        00:00:00 sshd: root@notty

root      1906  1902  0 03:42 ?        00:00:00 /usr/libexec/openssh/sftp-server

root      1913  1898  0 03:42 pts/1    00:00:00 -bash

root      1933     2  0 03:45 ?        00:00:00 [kworker/1:3]

root      1937     2  0 03:50 ?        00:00:00 [kworker/1:0]

root      1938  1913  0 03:51 pts/1    00:00:00 ping www.baidu.com

root      1939  1878  0 03:51 pts/0    00:00:00 ps -ef

 

>————————————————————————————————————————

结论：绝对路径和sh 会重新打开一个进程去执行脚本文件
source 默认在当前进程执行脚本，
默认丛当前进程查询变量默认从父进程查询变量
如果用export修饰变量，那么这个变量对于子进程就是课件的