Introduction to shell for loop and Array application

Read a file, assign each row to an array variable, and print it out in a for loop.

Copy codeThe Code is as follows :#! /Bin/sh
I = 1
SUM = 'sed-n' $ = 'tmp.txt '# calculates the total number of lines in the file.
Echo "$ SUM"
While read line
Do
Arr [$ I] = "$ line"
I = 'expr $ I + 1'
Done <tmp.txt
Echo "$ I"
I = 1
For I in 'seq $ Sum'; do
Echo "$ {arr [$ I]}"
Done

Appendix: shell array supplementary knowledge

I. Declare an array

1) array [key] = value # array [0] = one, array [1] = two
2) declare-a array # array is treated as the array name
3) array = (value1 value2 value3 ...)
4) array = ([1] = one [2] = two [3] = three ...)
5) array = "one two three" # echo $ {array [0 | @ | *]}. The array variable is treated as an array, but the array element only contains the string itself.

2. Access the Array

1) $ {array [key] }#$ {array [1]}

3. Delete Arrays

1) unset array [1] # Delete the first element in the array
2) unset array # Delete the entire array

4. Calculate the length of the array

1) $ {# array}
2) $ {# array [0]} # Same as above. $ {# Array [*]} and $ {# array [@]}. Note the difference between # {array: 0} and # {array: 0 }.