Connectors in the shell (and, and, or)

&& (and) with the || (OR) with the ; (and)

A semicolon has just been mentioned above for the delimiter between multiple commands. There are also two special symbols that can be used in the middle of multiple commands, that is, "&&" and "| |" are all listed below:

2. command1 command2             Span style= "Font-size:18px;color:rgb (255,0,0); font-weight:bold;" > and

4. command1 & & command2       and    

6. Command1 || command2 or

&& : The left command executes successfully before executing the command on the right.

  || : The left command executes unsuccessfully to execute the command on the right.

; (semicolon) : The left command executes successfully, and the command behind it executes.

When using ";", Command2 will be executed regardless of whether Command1 is executed successfully;

When using "&&", only if the Command1 is executed successfully, Command2 will execute, otherwise command2 not execute;

When using "| |", the Command1 execution succeeds Command2 not execute, otherwise go to execute Command2, in short Command1 and Command2 always have a command to execute.

before doing the experiment, want to remove all the test*, but the deletion, but the prompt said that the authority is not enough, the following is the process of troubleshooting:

[[email protected] ~]# rm-rf test*rm: Cannot delete "Test2/test1": Insufficient permissions RM: Unable to delete "Test2/test3": Insufficient permissions RM: Unable to delete "Test2/test4": Insufficient authority [[email protected] ~]# ls test*test1  test3  test4[[email protected] ~]# lsattr test*----- A-------e-test2/test1----i--------e-test2/test3-------------e-test2/test4[[email protected] ~]# chattr-a Test2/test1[[email protected] ~]# chattr-i test2/test3[[email protected] ~]# rm-rf test*rm: Cannot delete "test2/ Test1 ": Insufficient permissions RM: Cannot delete" TEST2/TEST3 ": Insufficient permissions RM: Unable to delete" Test2/test4 ": Insufficient permissions [[email protected] ~]# ls test*test1  test3  test4[[email protected] ~]# ls-ld test*drwxrwxr-x 2 root root 4096 May  10 10:12 test2[[email protect Ed] ~]# ls-l test2/*-rw-r--r--1 root root 6 May  10 10:20 test2/test1-rw-r--r--1 root root 0 May  10 10:11 test 2/test3-rw-r--r--1 root root 0 May  10 10:12 test2/test4[[email protected] ~]# lsattr test2/*-------------e-tes T2/test1-------------e-test2/test3-------------e-tesT2/test4[[email protected] ~]# lsattr test2-------------e-test2/test1-------------e-test2/ Test3-------------e-test2/test4[[email protected] ~]# lsattr-d test2----i--------e-test2[[email  Protected] ~]# chattr-i test2/[[email protected] ~]# rm-rf test2/

If you have done the same experiment before, I believe you will have the same problem. The next step is to illustrate the role of the two special symbols "&&" and "| |" By doing experiments:

[[email protected] ~]# Touch test1 test3[[email protected] ~]# ls test2 && touch test2ls: Unable to access test2: No that file or directory [[EM AIL protected] ~]# ls test2ls: Cannot access test2: No file or directory [[email protected] ~]# ls test2 | | Touch TEST2LS: Unable to access test2: No file or directory [[email protected] ~]# ls test*test1 test2 test3

This article from "12350027" blog, declined reprint!

Connectors in the shell (and, and, or)