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目录
简介一、分号二、&&三、||案例剖析
简介
在Linux中,可以使用分号”;”、双AND号”&&”和双竖线”||”来连接多个命令。根据不同场景,选择合适的符号使用。
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”?”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 BaseExceptionprint("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 BaseExceptionprint("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/bashpython cmd_1_success; python cmd_2_successpython cmd_1_success && python cmd_2_successpython 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_successcmd_1 start runcmd_1 do somethingcmd_1 endcmd_2 start runcmd_2 do somethingcmd_2 end第二种情况:cmd_1_fail; cmd_2_success
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseExceptioncmd_2 start runcmd_2 do somethingcmd_2 end
第三种情况:cmd_1_success; cmd_2_fail
cmd_1 start runcmd_1 do somethingcmd_1 endcmd_2 start runTraceback (most recent call last):File "cmd_2_fail.py", line 14, in run_fail_2()File "cmd_2_fail.py", line 9, in run_fail_2raise BaseExceptionBaseException
第四种情况:cmd_1_fail; cmd_2_fail
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseExceptioncmd_2 start runTraceback (most recent call last):File "cmd_2_fail.py", line 14, in run_fail_2()File "cmd_2_fail.py", line 9, in run_fail_2raise BaseExceptionBaseException
演示 && 的四类基本情况:
# 第一种情况:cmd_1_success && cmd_2_successcmd_1 start runcmd_1 do somethingcmd_1 endcmd_2 start runcmd_2 do somethingcmd_2 end第二种情况:cmd_1_fail && cmd_2_success
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseException
第三种情况:cmd_1_success && cmd_2_fail
cmd_1 start runcmd_1 do somethingcmd_1 endcmd_2 start runTraceback (most recent call last):File "cmd_2_fail.py", line 14, in run_fail_2()File "cmd_2_fail.py", line 9, in run_fail_2raise BaseExceptionBaseException
第四种情况:cmd_1_fail && cmd_2_fail
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseException
演示 || 的四类基本情况:
# 第一种情况:cmd_1_success || cmd_2_successcmd_1 start runcmd_1 do somethingcmd_1 end第二种情况:cmd_1_fail || cmd_2_success
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseExceptioncmd_2 start runcmd_2 do somethingcmd_2 end
第三种情况:cmd_1_success || cmd_2_fail
cmd_1 start runcmd_1 do somethingcmd_1 end
第四种情况:cmd_1_fail || cmd_2_fail
cmd_1 start runTraceback (most recent call last):File "cmd_1_fail.py", line 14, in run_fail_1()File "cmd_1_fail.py", line 9, in run_fail_1raise BaseExceptionBaseExceptioncmd_2 start runTraceback (most recent call last):File "cmd_2_fail.py", line 14, in run_fail_2()File "cmd_2_fail.py", line 9, in run_fail_2raise BaseExceptionBaseException
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。
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