Linux Shell脚本多命令执行逻辑的示例详解

目录

• 简介
• 一、分号
• 二、&&
• 三、||
• 案例剖析

简介

Linux 中可以使用分号";“、双and号”&&“和双竖线”||"来连接多个命令。根据场景的不同适当的使用合适的符号。

历史攻略

python：执行dos命令、Linux命令

命令连接符解析：

仅连接，表示运行先后，无逻辑关系：分号";"，如command1 ; command2

逻辑与关系：&&，如command1 && command2

逻辑或关系：&&，如command1 && command2

一、分号

命令之间没有逻辑关系。分号连接的命令会按照顺序从前向后依次执行，但分号两端的命令之间没有任何逻辑关系，所有写出来的命令最终都会被执行，即使分号前面的命令出错也不影响后面的命令。

二、&&

逻辑与。&&连接的命令会按照顺序从前向后执行，但只有当command1正确执行才执行command2，如果command1不正确执行，则不执行command2。在bash中，通过预定义变量“? ”来判断命令是否正确执行，如果 " ?”来判断命令是否正确执行，如果"?”来判断命令是否正确执行，如果"?"的值为0则表示前一条命令正确执行，其他任意值都表示不正确执行。

三、||

逻辑或。||连接的命令会按照顺序从前向后执行，但只有当command1不正确执行才执行command2，command1正确执行则不会执行command2。||和&&都是短路符号，符号左右的命令之间具有逻辑关系。

案例剖析

# -*- coding: utf-8 -*-
# time: 2022/10/4 21:47
# file: cmd_1_success.py
# 公众号: 玩转测试开发

def run_success_1():
    print("cmd_1 start run")
    print("cmd_1 do something")
    print("cmd_1 end")

if __name__ == '__main__':
    run_success_1()

cmd1_fail = python cmd_1_fail.py

# -*- coding: utf-8 -*-
# time: 2022/10/4 21:47
# file: cmd_1_fail.py
# 公众号: 玩转测试开发

def run_fail_1():
    print("cmd_1 start run")
    raise BaseException
    print("cmd_1 end")

if __name__ == '__main__':
    run_fail_1()

cmd2_success = python cmd_2_success.py

# -*- coding: utf-8 -*-
# time: 2022/10/4 21:49
# file: cmd_2_success.py

def run_success_2():
    print("cmd_2 start run")
    print("cmd_2 do something")
    print("cmd_2 end")

if __name__ == '__main__':
    run_success_2()

cmd2_fail = python cmd_2_fail.py

# -*- coding: utf-8 -*-
# time: 2022/10/4 21:51
# file: cmd_2_fail.py
# 公众号: 玩转测试开发

def run_fail_2():
    print("cmd_2 start run")
    raise BaseException
    print("cmd_2 end")

if __name__ == '__main__':
    run_fail_2()

即：存在4种基本情况

cmd_1_success、cmd_2_success
cmd_1_fail、cmd_2_success
cmd_1_success、cmd_2_fail
cmd_1_fail、cmd_2_fail

test.sh

#bin/bash
python cmd_1_success; python cmd_2_success
python cmd_1_success && python cmd_2_success
python cmd_1_success || python cmd_2_success

演示分号的四类基础情况：

# 第一种情况：cmd_1_success; cmd_2_success
cmd_1 start run
cmd_1 do something
cmd_1 end
cmd_2 start run
cmd_2 do something
cmd_2 end
# 第二种情况：cmd_1_fail; cmd_2_success
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException
cmd_2 start run
cmd_2 do something
cmd_2 end

# 第三种情况：cmd_1_success; cmd_2_fail
cmd_1 start run
cmd_1 do something
cmd_1 end
cmd_2 start run
Traceback (most recent call last):
  File "cmd_2_fail.py", line 14, in <module>
    run_fail_2()
  File "cmd_2_fail.py", line 9, in run_fail_2
    raise BaseException
BaseException

# 第四种情况：cmd_1_fail; cmd_2_fail
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException
cmd_2 start run
Traceback (most recent call last):
  File "cmd_2_fail.py", line 14, in <module>
    run_fail_2()
  File "cmd_2_fail.py", line 9, in run_fail_2
    raise BaseException
BaseException

演示 && 的四类基本情况：

# 第一种情况：cmd_1_success && cmd_2_success
cmd_1 start run
cmd_1 do something
cmd_1 end
cmd_2 start run
cmd_2 do something
cmd_2 end

# 第二种情况：cmd_1_fail && cmd_2_success
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException

# 第三种情况：cmd_1_success && cmd_2_fail
cmd_1 start run
cmd_1 do something
cmd_1 end
cmd_2 start run
Traceback (most recent call last):
  File "cmd_2_fail.py", line 14, in <module>
    run_fail_2()
  File "cmd_2_fail.py", line 9, in run_fail_2
    raise BaseException
BaseException

# 第四种情况：cmd_1_fail && cmd_2_fail
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException

演示 || 的四类基本情况：

# 第一种情况：cmd_1_success || cmd_2_success
cmd_1 start run
cmd_1 do something
cmd_1 end

# 第二种情况：cmd_1_fail || cmd_2_success
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException
cmd_2 start run
cmd_2 do something
cmd_2 end

# 第三种情况：cmd_1_success || cmd_2_fail
cmd_1 start run
cmd_1 do something
cmd_1 end

# 第四种情况：cmd_1_fail || cmd_2_fail
cmd_1 start run
Traceback (most recent call last):
  File "cmd_1_fail.py", line 14, in <module>
    run_fail_1()
  File "cmd_1_fail.py", line 9, in run_fail_1
    raise BaseException
BaseException
cmd_2 start run
Traceback (most recent call last):
  File "cmd_2_fail.py", line 14, in <module>
    run_fail_2()
  File "cmd_2_fail.py", line 9, in run_fail_2
    raise BaseException
BaseException

即：分号前后运行无逻辑关系；&&后面的命令需要前面的命令正常执行；

||后面的命令需要前面的命令运行失败才执行。

到此这篇关于Linux Shell脚本多命令执行逻辑的示例详解的文章就介绍到这了,更多相关Shell脚本多命令执行逻辑内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！