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May
5, 2003 (Tip) -
Creating
a Menu Using Select
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LiveFire
Labs' tip from last week explained what the PS2, PS3,
and PS4 shell variables were used
for. You may recall that PS3 is used
to re-define the prompt string displayed
to users when the select command is ready
to read a user's menu selection.
This week's tip takes a look at how a robust interactive menu
is easily created with the select command.
A frequently-used syntax for the select
command is:
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select
varname in opt1 opt2...optN
do
case $varname in
opt1) command1;;
opt2) command2;;
optN)
commandN;;
esac
done
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opt1-optN
represents valid menu options, and
command1-commandN represents the commands
that will be executed when the
corresponding menu option is selected by
the user.
The following example is a simple menu
that provides the user with system
information:
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PS3='Select
an option and press Enter: '
select i in Date Host Users Quit
do
case $i in
Date) date;;
Host) hostname;;
Users) who;;
Quit) break;;
esac
done
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When
executed, this example will display the
following:
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1) Date
2) Host
3) Users
4) Quit
Select an option and press Enter:
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If the user
selects 1, the system date is displayed
followed by the menu prompt:
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1) Date
2) Host
3) Users
4) Quit
Select an option and press Enter: 1
Mon May 5 13:08:06 CDT 2003
Select an option and press Enter:
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Pressing the
Enter key without making a selection will
re-display the menu and menu prompt:
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Select an option and press Enter:
1) Date
2) Host
3) Users
4) Quit
Select an option and press Enter:
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In the sample
code above, notice that PS3 has been
re-defined with a custom menu
prompt. If this line of code was
omitted the default menu prompt (#?)
would be displayed:
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1) Date
2) Host
3) Users
4) Quit
#?
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Learn
more...
If you are new to the UNIX or Linux
operating system and would like to learn
more about shells, shell commands, and
shell variables, you may want to consider
registering for LiveFire Labs' UNIX
and Linux Operating System Fundamentals
online training course.
If you already have a solid grasp of the
fundamentals but would like to learn more
about the Korn shell and basic and
advanced shell scripting, taking our Korn
Shell Scripting course will be
beneficial to you.
Our innovative hands-on training model
allows you to learn
UNIX by completing hands-on
exercises on real servers in our Internet
Lab.
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Tips...
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