Fifth chapter shell functions and Arrays

5.1 Functions

Format:

Func () {command}

Example 1:

#!/bin/bashfunc () {echo "This is a function."} Func# Bash Test.shthis is a function.

The shell function is simple, with the function name followed by a double parenthesis and the double curly brace. Called directly by the function name without parentheses.

Example 2: function return value

#!/bin/bashfunc () {var=$ () return $VAR echo "This is a function."} Funcecho $?# Bash TEST.SH2

Return is a function that defines the return value of a state, returns and terminates the function, but only returns a number, similar to exit 0.

Example 3: Function pass parameter

#!/bin/bashfunc () {echo "Hello $"}func world# bash Test.shhello World

Parameters are passed to the function via the shell position parameter.

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5.2 Arrays

An array is a collection of elements of the same type arranged in a certain order.

Format:

array= (element 1 element 2 element 3 ...)

The array is initialized with parentheses, and the elements are separated by a space.

Definition Method 1: Initialize array array= (a B C) Define Method 2: Create new array and add element array[]= element definition Method 3: command output as array element array= ($ (command))

Array operations:

Get all elements # echo ${array[*]} # * and @ both represent all elements a B c get array length # echo ${#array [*]}3 get first element # echo ${array[0]}a get second element # echo ${array[1]} b Get Third element # echo ${array[2]}c add element # array[3]=d# echo ${array[*]}a b c D add multiple elements # array+= (E F g) # echo ${array[*]}a b c d E F g Delete Except for the A element # unset Array[a] # Deleted by name will retain element subscript # echo ${array[*]}b c d E F g Delete first element # unset array[1] # echo ${array[*]}c d E F g

The array subscript starts with 0.

Example 1: A sequence of number sequences generated by the SEQ is put into the array

#!/bin/bashfor i in $ (SEQ 1 10); Do array[a]= $i let A++doneecho ${array[*]}# bash TEST.SH1 2 3 4 5 6 7 8 9 10 Delete Array # unset array

Example 2: Traversing an array element

#!/bin/baship= (192.168.1.1 192.168.1.2 192.168.1.3) for ((i=0;i<${#IP [*]};i++)]; Do echo ${ip[$i]}done# bash test.sh192.168.1.1192.168.1.2192.168.1.3

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Fifth chapter shell functions and Arrays