Carding the basic knowledge of shell script & lt; eight & gt;: process Control select
Select variable in list
Flag for the start of the do # loop
Every time a commands # loop variable takes a value, the loop body executes once
Flag for the end of the done # loop
The select loop is mainly used to create menus, and menu items in numerical order will be displayed on standard error, waiting for user input
The separator of the menu item is determined by the environment variable IFS
The prompt information used to guide the user to enter is stored in the environment variable PS3
If the user enters enter directly, the menu will be redisplayed
Similar to the for loop, omitting in list is equivalent to in "$*"
The user enters a number in the menu list and executes the corresponding command
The user's input is saved in the built-in variable REPLY.
Example 1
#! / bin/bash
#
# IFS is a system delimiter variable; if the input parameter variable is not specified, the system stores the parameters followed by the script in the REPLY variable by default
Clear
PS3= "What is your preferred OS?"
IFS=' |'
OS= "Linux | Gnu Hurd | FreeBSD | Mac OS X"
Select s in $OS
Do
Case $REPLY in
1 | 2 | 3 | 4) echo "You selected $s"
*) exit
Esac
Done
Execution result
1) Linux
2) Gnu Hurd
3) FreeBSD
4) Mac OS X
What is your preferred OS?1
You selected Linux
What is your preferred OS?4
You selected Mac OS X
What is your preferred OS?e
[root@localhost shell] #
Example 2
#! / bin/bash
#
# PS3 user-defined prompts
Clear
PS3= "What is your preferred scripting language?"
Select s in bash perl python ruby quit
Do
Case $s in
Bash | perl | python | ruby)
Echo "You selected $s"
Quit) exit
*) echo "You selected error,retry"
Esac
Execution result
1) bash
2) perl
3) python
4) ruby
5) quit
What is your preferred scripting language?1
You selected bash
What is your preferred scripting language?2
You selected perl
What is your preferred scripting language?5
[root@localhost shell] #
Example 3
#! / bin/bash
#
# Command package View script
PS3= "Select a program you want to execute:"
TOPLIST= "wget telnet htop atop nettop iftop ftop"
Clear
Select prog in $TOPLIST quit
Do
[[$prog = = quit]] & & exit
Rpm-Q $prog > / dev/null & & echo "$prog installed" | | echo "$prog is not installed"
Done
Execution result
1) wget 3) htop 5) nettop 7) ftop
2) telnet 4) atop 6) iftop 8) quit
Select a program you want to execute: 1
Wget installed
Select a program you want to execute: 8
[root@localhost shell] #
