（8） Shell function

#!/bin/bash

# 1. Shell function 

# 1.1  Function definition format 
:<<EOF
[ function ] funcname [()]
{
    
  action;
  [return int;]
}
# 1.  You can take function fun() Definition , It can also be direct fun() Definition , Without any parameters 
# 2.  Parameter return , Can display plus ：return  return , If not , The result of the last command will be returned as a result .
# 3. return Rear root value n(0-255)
EOF

# 1.2  example 1
demoFun()
{
    
  echo " This is my first  Shell  function "
}
echo "-------- The function starts executing --------"
demoFun
echo "-------- End of function execution --------"

# 1.3  example 2（ belt return sentence ）
funWithReturn()
{
    
  echo " Enter a number "
  read aNum
  echo " The number you enter is ${aNum}"
  return ${
    aNum}
}
funWithReturn
echo "funWithReturn The return value is  $? !" #  The return value of the function passes through  $?  To obtain a .
#  Function must be defined first , After the call 

# 1.  Function parameter 
#  Inside the body of the function , adopt  $n  To get the value of the parameter , for example ,$1 Represents the first parameter ,$2 Represents the second parameter ...
funWithParam()
{
    
  echo " The first 1 The parameter is  $1 ！"
  echo " The first 2 The parameter is  $2 ！"
  echo " The first 3 The parameter is  $3 ！"
  echo " The eleventh parameter is  ${11} !" #  Be careful ,$10  Can't get the tenth parameter , Getting the tenth parameter requires ${10}. When n>=10 when , Need to use ${n} To get the parameters .
  echo " The total number of parameters is  $#  individual ！"
  echo " Output all parameters as a string  $* !"
}
funWithParam 1 2 3 4 5 6 7 8 9 34 73

:<<EOF
$#  Number of arguments passed to script or function 
$*	 Display all the parameters passed to the script in a single string 
$$	 The current process the script runs ID Number 
$!	 Of the last process running in the background ID Number 
[email protected]	 And $* identical , But use quotation marks , And return each parameter in quotation marks .
$-	 Show Shell Current options used , And set Same command function .
$?	 Display the exit status of the last command .0 No mistakes , Any other value indicates an error .
EOF