bash Shell 编程练习 初步了解脚本的运行方式

1、编写第一个脚本source运行脚本

编辑sh01.sh
[root@linux1 sh]# vi sh01.sh
echo 1111
echo 'niu'
ls /
ll
echo $$
查看sh01.sh
[root@linux1 sh]# cat sh01.sh
echo 1111
echo 'niu'
ls /
ll
echo $$
运行sh01.sh
[root@linux1 sh]# source sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
total 4
-rw-r--r--. 1 root root 37 Feb 21 15:42 sh01.sh
6855

2、变成可执行文件

[root@linux1 sh]# chmod +x sh01.sh
看到bash id 发生了变化
[root@linux1 sh]# ./
-bash: ./: is a directory
[root@linux1 sh]# ./sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
./sh01.sh: line 4: ll: command not found
6890

3、使用bash 运行

去掉可执行文件
[root@linux1 sh]# chmod -x sh01.sh

[root@linux1 sh]# ll
total 4
-rw-r--r--. 1 root root 37 Feb 21 15:42 sh01.sh

先用source运行
[root@linux1 sh]# source sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
total 4
-rw-r--r--. 1 root root 37 Feb 21 15:42 sh01.sh
6855

使用bash运行
[root@linux1 sh]# bash sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
sh01.sh: line 4: ll: command not found
6900

4、bash 与pstree

[root@linux1 sh]# bash
[root@linux1 sh]# echo $$
6969
[root@linux1 sh]# pstree
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─bash───pstree
     │                    ├─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    └─man───sh───sh───less
     └─udevd───2*[udevd]
[root@linux1 sh]# exit
exit
[root@linux1 sh]# pstree
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    ├─man───sh───sh───less
     │                    └─pstree
     └─udevd───2*[udevd]

5、通过执行文件看不同的执行方式的差别

[root@linux1 sh]# ll
total 4
-rw-r--r--. 1 root root 44 Feb 21 16:20 sh01.sh
[root@linux1 sh]# echo $$
6855
[root@linux1 sh]# cat sh01.sh 
echo 1111
echo 'niu'
ls /
ll
echo $$
pstree

source 原父bash执行

[root@linux1 sh]# source sh01.sh 
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
total 4
-rw-r--r--. 1 root root 44 Feb 21 16:20 sh01.sh
6855
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    ├─man───sh───sh───less
     │                    └─pstree
     └─udevd───2*[udevd]
     
bash 新父bash执行

[root@linux1 sh]# bash sh01.sh 
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
sh01.sh: line 4: ll: command not found
7023
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─bash───pstree
     │                    ├─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    └─man───sh───sh───less
     └─udevd───2*[udevd]
     
.  原父bash执行

[root@linux1 sh]# . sh01.sh 
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
total 4
-rw-r--r--. 1 root root 44 Feb 21 16:20 sh01.sh
6855
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    ├─man───sh───sh───less
     │                    └─pstree
     └─udevd───2*[udevd]

查看当前进程树

[root@linux1 sh]# pstree
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    ├─man───sh───sh───less

变成可执行文件

[root@linux1 sh]# chmod +x sh01.sh
[root@linux1 sh]# ll
total 4
-rwxr-xr-x. 1 root root 44 Feb 21 16:20 sh01.sh

./  没有#! /bin/bash 时新父bash 执行
[root@linux1 sh]# ./sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
./sh01.sh: line 4: ll: command not found
7033
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─bash───pstree
     │                    ├─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    └─man───sh───sh───less
     └─udevd───2*[udevd]
     
加入 #! /bin/bash

[root@linux1 sh]# vi sh01.sh 

[root@linux1 sh]# cat sh01.sh 
#! /bin/bash
echo 1111
echo 'niu'
ls /
ll
echo $$
pstree

./  有#! /bin/bash 时 原子bash 执行
[root@linux1 sh]# ./sh01.sh
1111
niu
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  sbin  selinux  srv  sys  tmp  usr  var
./sh01.sh: line 5: ll: command not found
7039
init─┬─auditd───{auditd}
     ├─crond
     ├─master─┬─pickup
     │        └─qmgr
     ├─6*[mingetty]
     ├─rsyslogd───3*[{rsyslogd}]
     ├─sshd───sshd───bash─┬─man───sh───sh─┬─groff───grotty
     │                    │               └─less
     │                    ├─man───sh───sh───less
     │                    └─sh01.sh───pstree
     └─udevd───2*[udevd]