Linux Shell loop control characters and functions

loop control and functions

Break loop control, continue loop control.

Loop control character

The break loop control can be used to exit the entire loop;

After exiting the loop, the following loops are executed, using the Continue loop control;

#!/bin/bash

While True

Do

echo "Please enter a operation {1copy| 2delete|3backup|4exit} "

Read-p "Please enter Youroperation:" Op

Case $op in

1)

Continue

echo "Copy"

;;

2)

echo "Delete"

;;

3)

echo "Backup"

;;

4)

echo "Exit"

;;

*)

echo "error, try enter {1 | 2 |3 |4} again "

Esac

Done

function explanation

Basic knowledge of the definition of 1-2-1-functions

Invocation of the 1-2-2-function

Basic knowledge of function definition

If you run into a long path, make a variable.

Encounter a lot of repetitive operations, do a function can

Basic format of the function:

Name ()

{

Command1

Command2

...

}

Nginx ()

{

Netstat-anlpt | grep nginx

}

The title is the name of the function, the function body is a collection of commands within the function, in writing the script to pay attention to the title of the unique

An error occurs when the execution of a non-unique script

function does not allow empty commands-the collection of commands in the body of the function must contain at least one command

Define a function:

#!/bin/bash

Student () #定义函数

{

echo "Hello shell!" #函数中的命令

}

echo "Now going to run student ()"

Student

echo "End the student ()"

Effect:

[Email protected] shell]# sh for1.sh

Now going to run student ()

Hello shell! #函数的执行结果

End the student ()

Comments:

A simple function is defined in hanshu.sh

First execute echo "Start function student"

Execute the Student function

Finally execute echo "function Student execution End"

Functions, like scripts, are executed sequentially.

Student () { à function named student} represents the end

A reference to a parameter is passed

Environment:

Create A.txt

[email protected] shell]# Touch a.txt

To write a script:

Vim yinyong.sh

#!/bin/bash

Delete ()

{

RM-RF $

Mkdir$2

}

Delete/root/shell/aa.txt/root/shell/mydir

Perform

[Email protected] shell]# sh yinyoug.sh

[Email protected] shell]# ls-ld mydir/

Drwxr-xr-x. 2 root root 6 Sep 5 21:53 mydir/

Functions that call other modules

Functions that source calls other scripts

Define a module with different functions

[email protected] shell]# cat option.sh

#!/bin/bash

Delete ()

{

RM-RF $del

}

Copy ()

{

CP-FR $sdir $tdir

}

Backup ()

{

TARZCVF $tar _name $star _dir &>/dev/null

}

Quit ()

{

Exit

}

Edit a file again

#!/bin/bash

source/root/shell/option.sh

While True

Do

Cat <<eof

******************************

Thefollowing is optional

******************************

1) Copy

2) Delte

3) Backup

4) Exit

******************************

Eof

Read-p "Please enter youroptions:" option

Case $option in

1)

Read-p "Please input your want to copy the source file:" Sdir

Read-p "Please input your target directory:" Tdir

Copy

;;

2)

Read-p "Please input your target directory:" Del

Delete

;;

3)

Read-p "Please enter your backup file names:" Tar_name

Read-p "Please enter your backup file:" Tar_dir

Backup

;;

4)

Quit

Break

;;

*)

echo "$option is not optional operation"

Esac

Done

Shift Move Left

$ $4

$ $

Each time the parameter sequence moves left one position,

10 11 12 13

$ $4

#!/bin/bash #如果位置参数小于等于0

If [$#-le 0]

Then

echo "Error! Not enough parameters "#输出报错的信息

Exit 124

Fi #退出返回一个值

#定义一个sum变量

Sum=0

#如果位置参数大于0, it is established;

While [$#-GT 0]

Do

#运算 $sum +$1 and assignment to the variable sum

sum=$ (expr $sum + $)

#参数序列顺次左移一个位置

Shift

Done

Echo $sum

This article is from the "Technical Achievement Dream" blog, please be sure to keep this source http://andyliu.blog.51cto.com/518879/1846584

Linux Shell loop control characters and functions