Bash Shell Array

In bash shell, the handling of arrays is an error-prone place.

Array:
Variable: Stores the memory space of a single element;
Array: A contiguous memory space that stores multiple elements;
Array name
Index: Numbering starting from 0, is a numeric index;
Note: Indexes can also support the use of custom formats, not just numeric formats;
The bash array supports sparse formats, but does not store each number of elements in contiguous memory space

2. Declaring an array:
   Declare-a Array_Name
   Declare-a array_name: Associative array;

   
   

4. array element assignment:
        (1) assigns only one element at a time;
        Array_name[index]=value
           weekdays[0]= "Sunday"
            weekdays[4]= "Thursday"
        (2) assigns all elements at once:
       array_name= ("VAL1" "VAL2" "VAL3" ...)
        (3) assigns only specific elements:
       array_name= ([0]= "VAL1" [3]= "VAL2" ...)
        (4) read-a ARRAY

6. 
   References array elements: ${array_name[index]}
   Note: Omit [INDEX] to refer to the element labeled 0;
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   the length of the array (the number of elements in the array): ${#ARRAY_NAME [*]}, ${#ARRAY_NAME [@]}    &NBSP
   

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Example: Generate 10 random numbers to save in an array and find their maximum and minimum values;
#!/bin/bash
#
Declare-a Rand
Declare-i max=0
For i in {0..9}; Do
rand[$i]= $RANDOM
echo ${rand[$i]}
[${rand[$i]}-gt $max] && max=${rand[$i]}
Done
echo "Max: $max"
Example: Define an array in which the elements in the array are all files ending in. Log in the/var/log directory, and the sum of the number of rows in the file to be labeled as even;
#!/bin/bash
#
declare-a files
Files= (/var/log/*.log)
Declare-i lines=0
For I in $ (seq 0 $[${#files [*]}-1]); Do
If [$[$i%2]-eq 0];then
Let lines+=$ (Wc-l ${files[$i]} | cut-d "-F1)
Fi
Done
echo "Lines: $lines."
To reference an element in an array:
All elements: ${array[@]}, ${array[*]}

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Array slice: ${array[@]:offset:number}
Offset: Number of elements to skip
Number: The amount of elements to be fetched, all elements after the offset: ${array[@]:offset};

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Append an element to the array:
array[${#ARRAY [*]}]

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To delete an element in an array:
Unset Array[index]

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Associative arrays:
Declare-a Array_Name
Array_name= ([index_name1]= ' val1 ' [index_name2]= ' val2 ' ...)

Exercise: Generate 10 random numbers, ascending or descending sort;

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This article is from the "After Tomorrow" blog, please be sure to keep this source http://leeyan.blog.51cto.com/8379003/1694252

Bash Shell Array