Shell (7) User 2.16.doc

Command line parameters,
Positional Parameter

$0
Complete program name
(Basename
Command to remove the path
)

$1
The first parameter, exceeding
9
Hour
$ {10}

$ #
Number of parameters

$ *
All parameters in the command line, as a word

$ @
All parameters in the command line, used as multiple words

$
Current
Shell
Of
PID

$-Shell
Some attributes

$!
The previous background process
PID

 

Echo
'Basename $0'
#

Obtain the program name

Echo
$ {! #}


#

Obtain the last parameter

For (I = 1;
I <=$ #; ++ I); do
#

Traversal Parameters

Echo $ {! I}
#{}

Cannot be used
$

, Available
!

Substitution

Done

For
In $ @; do


#

Another Traversal method,
$ @

Change
$ *

Yes.

Echo $

Done

 

Shift
Command

Change the relative position of the command line parameter. The default value is left.
1
Bit, that is
$3
Change
$2
,
$2
Change
$1
,
$1
Discarded

Eg:
Another method for Traversing Parameters

While
[-N "$1"]; do

Echo $1

Shift

Done

 

Getopts
Analysis parameters

 

Read
, Get user input

Read


#
Read to variable
$ Reply
Medium

Read name
#
Read
Name

Read-P "input your name:" Name
#
With prompt
Read

Read name age

#
Read multiple variables separated by Spaces

Read-T 5 Name

#
Wait
5
Seconds, return failure

If
Read-T 5 name, then

Read
-N1-P "input [Y/n]" answer

#

Set the number of characters to read-read a single character, so that you do not need to press enter, in
Emacs

But the terminal can

Read
-S-p "input PWD" pwd

#

Do not show input,
Emacs

But the normal terminal can

 

Read
, Read files

Read once
1
Line, cannot directly take the file name as the parameter, you need to use
Cat
And other commands

Cat
A.txt | while read line
# Read

A redirected application?

Do

Echo $ line

Done

 

Output

Printf "format" A1 A2...

Eg:
Printf "af 0x % x" 11
#

Same format Controller
C