linux[Basic]-15-Simple shell script [01]

Understanding shell Scripts

The shell script works in two ways:

Interactive: Enter a command that the shell interprets and executes a command

Batch: Write many commands to the shell script, and the shell executes all commands at once

Shell a script is a program that combines various commands into logical statements

To view all the shell interpreters available in the system:

[Email protected] ~]# Cat/etc/shells

/bin/sh

/bin/bash

/sbin/nologin

/usr/bin/sh

/usr/bin/bash

/usr/sbin/nologin

/bin/tcsh

/bin/csh

[Email protected] ~]#

To view the current shell interpreter:

[Email protected] ~]# echo "$SHELL"

/bin/bash

[Email protected] ~]#

Write a simple shell script

Shell scripts should include:

Script Declaration, comment information, executable statement

Script Declaration (#! ): Tell the system which shell to use to explain

Comment Information (#): Introduction to Features

Executable statement: Execute a specific command

Instance:

[Email protected] sh]# vim example.sh

#!/bin/bash

#For Example by Msl23

# blog:www.cnblogs.com/msl23

Pwd

Ll-a

There are three ways to execute shell scripts:

Script file path:./example.sh

SH script file path: SH example.sh

Source script file path: source example.sh

The Sh and source methods can execute the script directly, but the method of accessing the script path directly

The Execute permission is required to execute the script

[Email protected] sh]#./example.sh

-bash:./example.sh:permission denied

[Email protected] sh]# chmod u+x example.sh #给属主用户加执行的权限

[Email protected] sh]#./example.sh

/root/lab1/sh

Receive User's parameters

The following are the shell predefined variables that have been defined

$	Current Execution Shell program name of the script
$1-9,${10},${11} ...	Positional Variables for parameters
$#	How many parameters are there?
$*	Values for all variables
$?	whether the previous command succeeded, succeeded 0 , failure not 0

Instance:

[Email protected] sh]# vim example_1.sh

#!/bin/bash

#Test parameter passing

#Author: Msl23 blog:www.cnblogs.cn/msl23

echo " this shell the script name is: $ "

echo " there are $# . parameters, respectively: $* "

echo " First parameter: $ $, third parameter: $ "

[Email protected] sh]# chmod u+x example_1.sh

[Email protected] sh]#./example_1.sh One, three four five six

The shell script program name is:./example_1.sh

There are a total of 6 parameters, namely: One twothree four five six

First parameter: One , third parameter:three

linux[Basic]-15-Simple shell script [01]