Linux?Shell腳本多命令執(zhí)行邏輯的示例詳解

更新時(shí)間：2022年10月16日 09:28:35 作者：玩轉(zhuǎn)測(cè)試開(kāi)發(fā)

Linux?中可以使用分號(hào)";“、雙and號(hào)”&&“和雙豎線”||"來(lái)連接多個(gè)命令。根據(jù)場(chǎng)景的不同適當(dāng)?shù)氖褂煤线m的符號(hào)，感興趣的小伙伴可以了解一下

簡(jiǎn)介

Linux 中可以使用分號(hào)";“、雙and號(hào)”&&“和雙豎線”||"來(lái)連接多個(gè)命令。根據(jù)場(chǎng)景的不同適當(dāng)?shù)氖褂煤线m的符號(hào)。

歷史攻略

python：執(zhí)行dos命令、Linux命令

命令連接符解析：

僅連接，表示運(yùn)行先后，無(wú)邏輯關(guān)系：分號(hào)";"，如command1 ; command2

邏輯與關(guān)系：&&，如command1 && command2

邏輯或關(guān)系：&&，如command1 && command2

一、分號(hào)

命令之間沒(méi)有邏輯關(guān)系。分號(hào)連接的命令會(huì)按照順序從前向后依次執(zhí)行，但分號(hào)兩端的命令之間沒(méi)有任何邏輯關(guān)系，所有寫(xiě)出來(lái)的命令最終都會(huì)被執(zhí)行，即使分號(hào)前面的命令出錯(cuò)也不影響后面的命令。

二、&&

邏輯與。&&連接的命令會(huì)按照順序從前向后執(zhí)行，但只有當(dāng)command1正確執(zhí)行才執(zhí)行command2，如果command1不正確執(zhí)行，則不執(zhí)行command2。在bash中，通過(guò)預(yù)定義變量“? ”來(lái)判斷命令是否正確執(zhí)行，如果 " ?”來(lái)判斷命令是否正確執(zhí)行，如果"?”來(lái)判斷命令是否正確執(zhí)行，如果"?"的值為0則表示前一條命令正確執(zhí)行，其他任意值都表示不正確執(zhí)行。

三、||

邏輯或。||連接的命令會(huì)按照順序從前向后執(zhí)行，但只有當(dāng)command1不正確執(zhí)行才執(zhí)行command2，command1正確執(zhí)行則不會(huì)執(zhí)行command2。||和&&都是短路符號(hào)，符號(hào)左右的命令之間具有邏輯關(guān)系。

案例剖析

# -*- coding: utf-8 -*-
# time: 2022/10/4 21:47
# file: cmd_1_success.py
# 公眾號(hào): 玩轉(zhuǎn)測(cè)試開(kāi)發(fā)


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
# 公眾號(hào): 玩轉(zhuǎn)測(cè)試開(kāi)發(fā)


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
# 公眾號(hào): 玩轉(zhuǎn)測(cè)試開(kāi)發(fā)


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種基本情況

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

演示分號(hào)的四類(lèi)基礎(chǔ)情況：

# 第一種情況：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
# 第二種情況：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

# 第三種情況：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

# 第四種情況：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 && 的四類(lèi)基本情況：

# 第一種情況：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

# 第二種情況：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

# 第三種情況：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

# 第四種情況：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 || 的四類(lèi)基本情況：

# 第一種情況：cmd_1_success || cmd_2_success
cmd_1 start run
cmd_1 do something
cmd_1 end

# 第二種情況：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

# 第三種情況：cmd_1_success || cmd_2_fail
cmd_1 start run
cmd_1 do something
cmd_1 end

# 第四種情況：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：分號(hào)前后運(yùn)行無(wú)邏輯關(guān)系；&&后面的命令需要前面的命令正常執(zhí)行；

||后面的命令需要前面的命令運(yùn)行失敗才執(zhí)行。

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