Shell Programming (Functions)

declaring functions

Demofun () {    echo" This is my first shell function! " }

Function name () {

... function body

}

In the shell, arguments can be passed to a function when it is called. Inside the function body, the value of the parameter is obtained in the form of a $n, for example, $ $ for the first argument, and $ = for the second argument ...

Funwithparam () {Echo "The first parameter is $!"    Echo "The second parameter is a $!"    Echo "the tenth parameter is $ A!"    Echo "the tenth parameter is ${10}!"    Echo "the 11th parameter is ${11}!"    Echo "The total number of parameters is $#!"    Echo "output all parameters as a string $*!"}

Function call

Function Name parameter 1 parameter 2

Eg: Enter an IP address the last one to start, automatically find out which host address in the network segment online

#!/bin/Bash#checkonline () {ADDR=$1        if Ping-C1$ADDR &>/dev/NULL         Thenreturn0        Elsereturn1        fi}if[" $"-gt0-A" $"-gt0-A" $"-lt" $"]2>/dev/NULL Then         for((i=$1; i<$2; i++))         Do                ifCheckonline192.168.1. $i Then                        Echo "192.168.1. $i is online"                fi         DoneElse        Echo "parameter is not correct"fi

Summarize

A method of judging whether a variable is a numeric type

# # method 1#if["$"-gt 0] 2>/dev/null; then#  Echo "is number ." #else #  Echo 'No.' #fi# # Method 2, Case # Case " $" inch #  [1-9][0-9]*)  #    Echo "is number ." #    ;; #  *)  #    ;; #Esac# # Method 3,Expr Expr$1 "+" Ten&>/dev/NULLif[$?-eq0]; Then  Echo " $ is number"Else  Echo " not number"fi

Shell Programming (Functions)