Linux01-bash function Programming 42

First, the function

1, Function: Functions, functions

2. function: To encapsulate a particular function or code that should be executed independently into a separate function and take a name, call it when used;

3. function Features: Structured programming, can not be run independently, need to be executed when the call, may be called multiple times;

Second, function programming and application

1, define a function, method one:

function FUNCNAME {

Command (commands that are executed independently)

}

2. Define a function, method two:

FUNCNAME () {

Command

}

3. function Custom Execution status return value: Return #

#表示: 0-255

4. functions that accept parameters: ./shellname.sh m N

Parameter $1:m

Parameter $2:n

such as 1:

#!/bin/bash

#

ShowMenu () {

Cat << EOF

d| D) show disk usages.

m| M) show menory usages.

s| S) show swap usages.

q| Q) quit.

Eof

}

ShowMenu

Read-p "Your is choice:" Choice

until [$CHOICE = = ' Q '-o $CHOICE = = ' Q '];d o

Case $CHOICE in

d| D

DF-HP;;

m| M

free-m | grep "^mem";;

s| S

free-m | grep "^swap";;

*)

Read-p "Your is choice again:" Choice;;

Esac

ShowMenu

Read-p "Your is choice:" Choice

Done

such as 2:

#!/bin/bash

#

ADDUSER () {

Username=user20

if! Id-u $USERNAME &>/dev/null;then

Useradd $USERNAME

echo $USERADD | passwd--stdin $USERADD &>/dev/null

return 0

Else

Return 1

Fi

}

ADDUSER

If [$? = = 0];then

echo "user add finished."

Else

echo "User add Failuer."

Fi

such as 3:

#!/bin/bash

#

Twosum () {

Echo $[$1+$2]

}

For I in {1..10};d o

Let j=$[$I +1]

echo "$I plus $J ' twosum $I $J '"----> Pass 2 parameters

Done

Practice, write a script:

Determine which hosts are online between 192.168.0.200-192.168.0.254. Requirements:

1, the use of functions to achieve a host of the decision process;

2. Call this function in the main program to determine the online status of all hosts within the specified range.

Method One:

#!/bin/bash

#

PING () {

For I in {1..10};d o

If Ping-c 1-w 1 192.8.8. $I &>/dev/null;then

echo "192.8.8. $I is up."

Else

echo "192.8.8. $I is down."

Fi

Done

}

Ping

Method Two:

#!/bin/bash

#

PING () {

If Ping-c 1-w 1 $ &>/dev/null;then

echo "is up."

Else

echo "is down."

Fi

}

For I in {1..10};d o

PING 192.8.8. $I

Done

Method Three:

#!/bin/bash

#

PING () {

If Ping-c 1-w 1 $ &>/dev/null;then

return 0

Else

Return 3

Fi

}

For I in {1..10};d o

PING 192.8.8. $I

If [$? = = 0];then

echo "192.8.8. $I is up."

Else

echo "192.8.8. $I is down."

Fi

Done

Write a script: Use the function to complete

1, the function can accept a parameter, the parameter is the user name;

Determine if a user exists

Returns the shell and UID of this user if it exists, and returns the normal status value;

If it does not exist, it says that the user does not exist and returns an error status value;

2, the function is called in the main program;

Extension 1: In the main program, let the user enter the user name, passed to the function to judge;

Extension 2: In the main program, after entering the user name judgment does not exit the script, but prompts the user to continue to enter the next user name;

If the user entered the user does not exist, please re-enter the user, but if the user entered Q or Q to exit;

Reference:

#!/bin/bash

#

USER () {

If id-u $ &>/dev/null;then

echo "is UID and SHELL: ' grep" ^$1 "/etc/passwd | cut-d:-f3,7 ' "

return 0

Else

echo "Not user $"

Return 5

Fi

}

Read-p "Your input username:" Username

until [$USERNAME = = Q-o $USERNAME = = Q];d o

USER $USERNAME

If [$? = = 0];then

Read-p "Your input username:" Username

Else

Read-p "Your input username again:" username

Fi

Done

This article is from "Nick Liu's blog," Please make sure to keep this source http://zkhylt.blog.51cto.com/3638719/1411508