Shell (4) mongo.doc

1)



Create

Function
Name {

...

}

Or:

Name (){

...

}

 

2)



Call

Use the function name directly. The function can be called only after it is defined;

When a function has the same name, the new definition will overwrite the old definition and no alarm is triggered;

 

3)



Exit

Use
Return

 

4)



Return Value

Function exit status, variable available
$?
Get --
$?
It is always the result of the last command. Therefore, the return value must be obtained as soon as possible after the function returns, otherwise it will be overwritten by the return of the new command;

L



The default return value is the return value of the last command;

L



Use"
Return n
"Return,
N
Is an integer in the range
0
~
255
;
TBD
, Can only be used
$?
Get results?

L



Use
Shell
Variable storage return value, which can be used for any type of Return Value -- Use
Echo
Output

Eg:

Function
A {

Echo "XXXX"

Read-T 3-P "input ......"
#

Output
Stdout

Of
Input something

Not part of the returned result

Echo 1000

Echo $…

}

 

Rlt = 'A'

#

The returned values are stored in
Rlt

Echo
$ Rlt

# Rlt


Is all
Echo


Output Combination

If the method in the example is used, the function is used as a sub-process.
Exit
It cannot be used to exit the script; in addition, it can still be used
$?
Obtain Functions
Return
(Or
Exit
;

TBD

: How to make some of them
Echo
Not as function output?

Method:
Echo
Redirect
Stderr
;

 

5)



Passing Parameters

Bash
Process a function as a small script. You can also pass the parameter named
$0
, The parameter is
$1
,
$2
And so on

Call Method for passing Parameters

Result = 'a 1 abc'

 

6)



Global Variables

By default, all variables defined in the script are global variables, and functions can access their externally defined variables-bad style

Eg:

Function
A {

C = dddd
#

Variables defined in the function

Echo $ C

}

C = 1111.

Echo
$ C

A

# C

Value changed

Echo
$ C

 

7)



Local variable, use
Local

Eg:

Function
A {

Local C = dddd
#

Define local variables

Echo $ C

}

C = 1111.

Echo
$ C

A

Echo
$ C
# C

Value is not function
A

Change

 

8)



Recursion

Eg
, Implement factorial
X! = X * (x-1 )!

Function
X {

If [$1-EQ 1]; then

Echo $1

Else

Local TMP = $ [$1-1]

Echo $[$1 * 'x $ TMP ']

Fi

}

 

Ret = 'x
5'

Echo $ RET

 

9)



Function library

Create: Write the function to an independent file, as shown in figure
AAA. t

Library problem: the function is the same as the environment variable, only when it is created
Shell
Valid;

Usage:
Source
Command in the current
Shell
To execute commands;

Source
Alias:
Dot operator

Not used
Source
Command to create a new
Shell
Execute commands to face the above problems;

Eg
, Reference
Aaa
Library:

.
./AAA. t

 

Source
The command is equivalent
# Include
Used to import files. Then, the functions in the file can be called directly.