Common usage and examples of arrays in shell programming under Linux

A new version of Bash supports one-dimensional arrays. Array elements can be initialized using the notation variable[xx]. Alternatively, the script can use the DECLARE-A variable statement to specify an array, and so on. To refer to an array element (that is, the value), you can use curly braces, Access form ${variable[xx]}, of course, the following are some of the old boys often used methods and a little understanding of the array, if there is advice, welcome guidance, thank Bo friends first.

Common definition methods for 1.1 shell arrays:

1) Method One:

Command law:

Dir= ($ (ls.))

Example 1: Manual command-line Operation demo

[Root@oldboy scripts]# dir= ($ (ls.))

[Root@oldboy scripts]# ls.

Oldboy.log apachemon.sh Httpdctl

[Root@oldboy scripts]# echo ${#dir [*]} <== View the length of the array

3

Command line loop to print a group element:

Writing 1:

for ((i=0; i< ' echo ${#dir [*]} '; i++))

Todo

Echo-e "${dir[$i]}\n"

Done

Tip:i< ' echo ${#dir [*]} ' can be replaced with a simpler i<${#dir [*]}, (Thanks to the eternal Night Brothers).

====================================

Writing 2:

for ((i=0; i<${#dir [*]}; i++))

Todo

Echo-e "${dir[$i]}\n"

Done

====================================

Writing 3:

For ((i=0;i<${#dir [@]};i++))

Todo

echo ${dir[${i}]}

Done

Example 2: Define and output array elements by script:

[Root@oldboy scripts]# Cat printarray.sh

Dir= ($ (ls.))

for ((i=0; i<${#dir [*]}; i++))

Todo

Echo-e "${dir[$i]}\n"

Done

[Root@oldboy scripts]# SH printarray.sh

Oldboy.log

apachemon.sh

Httpdctl

printarray.sh

====================================================

2) Method Two: Enumerating Element method

array= (red green blue Yellow magenta)

Array= (

Oldboy

Zhangyue

Zhangyang

)

Example 3: Scripting examples of enumerating element methods

[Root@oldboy ~# Cat test.sh

Array= (

Oldboy

Zhangyue

Zhangyang

)

for ((i=0; i< ${#array [*]}; i++))

Todo

echo "${array[$i]}"

Done

Echo----------------------

echo "Array len:${#array [*]}"

[Root@oldboy ~# SH test.sh

Oldboy

Zhangyue

Zhangyang

Array Len:3

3 Method 3: In fact, method three and one of the same, because of good actual combat value so separate list of explanations

Judge= ($ (curl-i-S ${url_list[$i]}|head-1|tr "\ r"))

Example 4: A more professional production check URL address script (Shell array method):

[Root@oldboy ~]# Cat check_url.sh

#!/bin/bash

# This script are created by Oldboy.

# e_mail:31333741@qq.com

# qqinfo:49000448

# Function:check Web URL

# version:1.1

. /etc/init.d/functions

Url_list= (

http://etiantian.org

Http://www.linuxpeixun.com

Http://oldboy.blog.51cto.com

)

function Wait ()

{

Echo-n ' 3 seconds to perform the operation. '

For ((i=0;i<3;i++))

Todo

Echo-n "."; Sleep 1

Done

www.bianceng.cn

Echo

}

function Check_url ()

{

Wait

echo ' Check URL ... '

for ((i=0; i<${#url_list [*]}; i++))

Todo

# http/1.1 OK

Judge= ($ (curl-i-S ${url_list[$i]}|head-1|tr "\ r"))

if [[[${judge[1]} ' = = ' && ' ${judge[2]} ' = = ' OK ']]

Then

Action "${url_list[$i]}"/bin/true

Else

Action "${url_list[$i]}"/bin/false

Fi

Done

}

Check_url

[Root@oldboy ~]# SH check_url.sh

After 3 seconds, perform the operation ....

Check URL ...

http://etiantian.org [OK]

http://www.linuxpeixun.com [OK]

http://oldboy.blog.51cto.com [OK]

Hint: The above results are colored.