Shell Foundation V: Array Preliminary

First, an array overview

Arrays: Data Structures

Data series, continuous multiple data, can be used to get related elements of the index

Declaring an array:declare-e arrayname

Initialization assignment:arrayname= ("STRING1" "STRING2" ... )

Arrayname= ("STRING1" [4]= "STRING2" ...)

arrayname=arrayname[0]= "STRING1" arryname[3]= "STRING"

get all the elements in the array:${arraryname[@],${arrayname[*]}

Gets the total number of valid elements in the array:${#ARRAYNAME [@]},${#ARRAYNAME [*]}

Gets the length of the string in an element:${#ARRAYNAME [INDEX]} (index=0,1,2,3 ...)

Cases:

[[email protected] shell]# echo ${color[0]}red[[email protected] shell]#  echo ${color[1]}bule[[email protected] shell]# echo ${color[2]}gree[[email  protected] shell]# echo  $color [2] red[2][[email protected] shell]# echo   $color           #数组不指定引用其第几个元素默认是引用第一个元素red [[email  protected] ~]# x= (nihao  "s b"  [4]= ' Ruozhi ') [[Email protected] ~]# echo  ${x[5]}                [ [Email protected] ~]# echo ${x[2]}[[email protected] ~]# echo ${x[1]}s  b[[email protected] ~]# echo ${x[4]}ruozhi[[email protected] ~]# x= ( 333 22 4444 555555555) [[email protected] ~]# echo ${#x [1]}2[[email  Protected] ~]# echo ${#x [3]}9 

Two, bash pseudo-random number generator

$RANDOM

Practice:

1. Print 99 multiplication table

[[Email protected] shell]# cat 12.sh#!/bin/bashn= (' 1 '   ' 2 '   ' 3 '   ' 4 '   ' 5 '   ' 6 '   ' 7 '   ' 8 '   ' 9 ') for x in $ (seq 0 8);d o     for y in $ (seq 0  $x);d o        echo -e  -n  "${n[y]}x${n[x]}=$[${n[x]}*${n[y]}]\t"         done    echodone[[email protected] shell]# bash 12.sh1x1=11x2=2   2x2= 41x3=3   2x3=6   3x3=91x4=4   2x4=8   3x4=12   4x4=161x5=5   2x5=10  3x5=15  4x5=20  5x5=251x6=6    2x6=12  3x6=18  4x6=24  5x6=30  6x6=361x7=7    2x7=14  3x7=21  4x7=28  5x7=35  6x7=42  7x7=491x8=8    2x8=16  3x8=24  4x8=32  5x8=40  6x8=48  7x8=56  8x8=641x9= 9   2x9=18  3x9=27  4x9=36  5x9=45  6x9=54   7x9=63  8x9=72  9x9=81

1. Generate N random numbers (n>5) by script, sort them from small to large (bubble sort)

3. Select random bits from all the students

Shell Foundation V: Array Preliminary