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Shell_ 04_ Shell script
2022-07-06 16:50:00 【Coke loving w】
Shell_04_Shell Script
Shell Script
Script : A file consisting of multiple commands ( It can be viewed through a text editor )
1)Shell Belong to Linux Built in scripts ( Common scripts :JS、JSP、PHP、SQL、Python etc. )
2) Script cycle : One Shell The process of file operation completion
3)Shell Scripts are divided into : Simple writing ( The accumulation of simple commands )、 Complex writing ( Programming )
To write Shell Script
To write Shell The script should follow the following rules :
(1) File name specification
1) File name naming format : file name .sh
//.sh The suffix is to distinguish ordinary files , And .sh yes Bash Default suffix
(2) Code specification
1)Shell The first line in the script file must be :#!/bin/bash
// Indicates the Shell Interpreter
2) Script to “exit N” Form ends (N Is the returned value ), And N The scope is 0~255
// It can be done by ${?} get N Value , Easy to adjust
// if N The value of exceeds 255, Then divide the value by 256 The remainder of is used as the return status code
Common exit status codes
Status code | explain |
---|---|
0 | The command ended successfully |
1 | Invalid parameter |
2 | Not suitable Shell command |
126 | Command execution failed ( No authority ) |
127 | No specified command |
128 | Invalid exit parameter |
128+x | x Signal related errors |
130 | By Ctrl+C End |
255 | Exit status code out of normal range |
(3) Annotation specifications
1) Notes should include : Script function 、 Version information and environment required for operation
// It is better to include : author 、 Contact information 、 History of script and special commands of script
(4) Call specification
1) The calling of the script requires the user to have the execution permission of the file (x);
2) Script files can be called by :
Script path 、sh Script name 、source Script name
// The first two methods are both sub Shell Execute script in , and source Then in the parent Shell Execute script in
(5) Special symbols
Special symbols | meaning |
---|---|
# | Annotation symbols |
; | Command separator |
& | Commands become background tasks |
Such as : Use Shell Script program , Output “Hello world!”
1)a. Create with .sh Suffix script file
1)b. Write relevant programs ( The first line specifies the interpreter ), And save
1)c. Give script execution permission , Call script
2)a. Create and write hello.sh Script files
2)b. The contents of the script file are as follows :
// It is strongly recommended to use the second way , It can ensure the maintenance and update of subsequent scripts
// Scripting tools are best used Vim instead of Vi(Vim There is additional syntax detection function )
trap command : Set when Shell The response of the script after receiving the signal
Command format 1:trap command The signal
1) After receiving the specified signal , Run the specified command ;
2) Multiple trap On command , Then only run this trap Command related parts , To execute the specified command ;
Such as : Use Ctrl+C Termination with trap Command the script that captures the signal
1) To write test23.sh Script files
2) call test23.sh Script files
Command format 2:trap Single dash or double dash The signal // Restore the function of the signal generator
1) If the signal is captured before recovery , According to trap The command specified by the command executes
Such as : adopt trap After the command captures the signal , Restore the function of the signal generator
1) To write test24.sh Script files
2) call test24.sh Script files
call Shell Script
sh command :shell command interpreter
Command format :sh Options File path
1) The most commonly used is to make the system with Bash Function execution file
2)sh Is to execute the script file in the subprocess
Options | meaning |
---|---|
-v | perform shell Before script , First output the content to the screen |
-n | Only right shell Script syntax checking , Not implemented |
-x | Yes shell The script tracks each statement |
// The most commonly used -x Option to modify the script file debug
Such as : Yes hello.sh Document carried out shell Script tracking and debugging
source command : At present Bash Execute the document in the environment and take effect immediately
Command format :source File path
1)source The command is also “.” Click command ( They're exactly the same )
2)source The command is often used to execute the initialization file just modified , Make the document effective immediately
3)source Is to execute the script file in the parent process
Other ways to call Shell Script :
1) Call with absolute path or relative path ;
2) adopt Shell The absolute path of the interpreter and the path of the script file are called ;
// Such as :/bin/bash File path
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