Shell Script Learning Note nine: Shell functions

The definition format of the function:

function Funname ()

{

Action

return xxx;

}

1, can be with function fun () definition, can also be directly fun () definition, without any parameters

2, the parameter returns, can display add: return returns, if not added, will run the result as the last command, as the return value. return followed by value n

1. function without return statement

Demofun () {    echo" This is a shell function "echo" -----Function starts executing----- " Demofun Echo " -----function is finished----- "

2. function with return statement

 funcwithresult () { echo  "   This function adds two numbers to the input   ;  echo   "     Enter the first number:   " ;    Read Anum;  echo   "     Enter a second number:     echo   "  The sum of the two numbers entered is: $?   " 

Note:

1, function return value after calling this function through $? To obtain;

2, all functions must be defined before use, the calling function only uses the name of its functions;

3. Function parameters

Demofun () {Echo "The first parameter , $"    Echo "The second parameter, a"    Echo "Tenth parameter $ A"    Echo "Tenth parameter ${10}"    Echo "The total number of parameters is $#"    Echo "output all parameters as a string $*"} demofun1 2 3 4 5 6 7 8 9  the  -

Note: $ $ cannot get the tenth parameter, and the tenth parameter requires ${10}. When n>=10, you need to use ${n} to get the parameters

Special parameters:

$# the number of arguments passed to the script

$* Displays all parameters passed to the script in a single string

$$ The current process ID number for the script to run

$! ID number of the last process running in the background

[Email protected] same as $*, but quoted when used, and returns each parameter in quotation marks.

$- shows the current options that the shell uses, as is the SET command function.

$? Displays the exit status of the last command. 0 means there is no error, and any other value indicates an error.

Shell Script Learning Note nine: Shell functions