1. Define the function and reference inside the shell file:
Copy CodeThe code is as follows:
[~/shell/function]# Cat factorial.sh
#!/bin/bash
function factorial
{
Factorial=1
For ((I=1;i <= $1;i++))
Do
factorial=$[$factorial * $i]
Done
The factorial of Echo $ is: $factorial
}
Echo ' program name ': $, for factorial
Factorial $
[~/shell/function]#./factorial.sh 10
Program name:./factorial.sh, used to find factorial
The factorial of 10 is: 3628800
2. Return value
function return code refers to the status code of the last command of the function, which can be used for function return values
Use the return command to manually specify the return value:
Copy CodeThe code is as follows:
[~/shell/function]# Cat return.sh
#!/bin/bash
function Fun1 {
Read-p "Enter a:" A
Echo-n "Print 2a:"
Return $[$a * 2]
}
Fun1
echo "return value $?"
[~/shell/function]#./return.sh
Enter a:100
Print 2a:return Value 200
Because the shell status code is 255 maximum, an error occurs when the return value is greater than 255.
Copy CodeThe code is as follows:
[~/shell/function]#./return.sh
Enter a:200
Print 2a:return Value 144
3. Function output
To return numbers, floating-point numbers, and string values greater than 255, it is best to use a function to output to a variable:
Copy CodeThe code is as follows:
[~/shell/function]# Cat./fun_out.sh
#!/bin/bash
function Fun2 {
Read-p "Enter a:" A
Echo-n "Print 2a:"
echo $[$a * 2]
}
result= ' fun2 '
echo "Return value $result"
[~/shell/function]#./fun_out.sh
Enter a:400
return value Print 2a:800
4. Pass parameters to the function (using positional parameters):
Copy CodeThe code is as follows:
[~/shell/function]# Cat./parameter.sh
#!/bin/bash
If [$#-ne 3]
Then
echo "Usage: $ A b C"
Exit
Fi
Fun3 () {
Echo $[$ * $ * $
}
Result= ' Fun3 $ $
echo the result is $result
[~/shell/function]#./parameter.sh 1 2 3
The result is 6
[~/shell/function]#./parameter.sh 1 2
Usage:./parameter.sh a B C
5. Global variables and local variables
By default, variables created in the function and shell bodies are global variables that can be referenced to each other, and may affect each other when the shell body part and the function part have the same name variables, for example:
Copy CodeThe code is as follows:
[~/shell/function]# Cat./variable.sh
#!/bin/bash
If [$#-ne 3]
Then
echo "Usage: $ A b C"
Exit
Fi
Temp=5
Value=6
Echo Temp is: $temp
echo value is: $value
Fun3 () {
Temp= ' echo ' scale=3;$1*$2*$3 ' | Bc-ql '
result= $temp
}
FUN3 $ $
echo "The result is $result"
If [' echo ' $temp > $value ' | bc-ql '-ne 0]
Then
echo "Temp is larger"
Else
echo "TEMP is still smaller"
Fi
[~/shell/function]#./variable.sh 12 3 2
Temp Is:5
Value Is:6
The result is 72
Temp is larger
In this case, it is best to use local variables inside the function to eliminate the effect.
Copy CodeThe code is as follows:
[~/shell/function]# Cat./variable.sh
#!/bin/bash
If [$#-ne 3]
Then
echo "Usage: $ A b C"
Exit
Fi
Temp=5
Value=6
Echo Temp is: $temp
echo value is: $value
Fun3 () {
Local temp= ' echo ' scale=3;$1*$2*$3 ' | Bc-ql '
result= $temp
}
FUN3 $ $
echo "The result is $result"
If [' echo ' $temp > $value ' | bc-ql '-ne 0]
Then
echo "Temp is larger"
Else
echo "TEMP is still smaller"
Fi
[~/shell/function]#./variable.sh 12 3 2
Temp Is:5
Value Is:6
The result is 72
Temp is still smaller
6. Pass an array variable to the function:
Copy CodeThe code is as follows:
[~/shell/function]# Cat array.sh
#!/bin/bash
A= (11 12 13 14 15)
Echo ${a[*]}
function Array () {
echo Parameters: "[email protected]"
Local factorial=1
For value in "[Email protected]"
Do
factorial=$[$factorial * $value]
Done
Echo $factorial
}
Array ${a[*]}
[~/shell/function]#./array.sh
11 12 13) 14 15
Parameters:11 12 13 14 15
360360
7. function returns an array variable
Copy CodeThe code is as follows:
[~/shell/function]# Cat array1.sh
#!/bin/bash
A= (11 12 13 14 15)
function Array () {
echo Parameters: "[email protected]"
Local newarray= (' echo ' [email protected] ')
Local element= "$#"
Local I
for ((i = 0; i < $element; i++))
{
newarray[$i]=$[${newarray[$i]} * 2]
}
echo New value:${newarray[*]}
}
result= ' array ${a[*]} '
Echo ${result[*]}
[~/shell/function]#./array1.sh
Parameters:11 New Value:22 24 26 28 30
From:http://www.jb51.net/article/57951.htm
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7 Ways to use shell functions
