Sunday, March 30, 2008
Creating menus using select - BASH
The select construct is adopted from the Korn Shell and is a good tool for building menus.
The basic usage:
select variable [in list]
do
command...
break
done
This prompts the user to enter one of the choices presented in the variable list.
Note: select uses the PS3 prompt by default.
A simple script to start with.
$ cat se3.sh
#!/bin/bash
PS3='Your Favourite Shell ?' # Set the prompt string
echo
select shell
do
echo
echo "You have selected: $shell"
echo
break #This break is important and must
done
exit 0
Executing:
$ ./se1.sh
1) ksh
2) bash
3) sh
4) zsh
5) csh
Your Favourite Shell ?2
You have selected: bash
List is omitted:
If "in list" is not mentioned, select picks the list of command line arguments ($@) passed to the script or to the function in which the select construct is embedded. See "se3.sh" script below:
$ cat se3.sh
#!/bin/bash
PS3='Your Favourite Shell ?' # Set the prompt string
echo
select shell
do
echo
echo "You have selected: $shell"
echo
break #This break is important and must
done
exit 0
Executing:
$ ./se3.sh bash ksh zsh
1) bash
2) ksh
3) zsh
Your Favourite Shell ?1
You have selected: bash
Using select in a function:
$ cat se6.sh
#!/bin/bash
PS3='Your Favourite Shell ?' # Set the prompt string
echo
f_choose () {
select shell
do
echo
echo "You have selected: $shell"
echo
break #This break is important and must
done
}
f_choose "bash" "ksh" "csh" "zsh"
exit 0
Executing:
$ ./se6.sh
1) bash
2) ksh
3) csh
4) zsh
Your Favourite Shell ?3
You have selected: csh
A practical example:
$ cat sel.sh
#!/bin/bash
f_Add () {
echo "Inside Add Function"
}
f_Delete () {
echo "Inside Delete Function"
}
f_Update () {
echo "Inside Update Function"
}
PS3='Your Menu ? ' # Set the prompt string
echo
select item in "Add" "Delete" "Update" "quit"
do
#Handling default case in select
if ! test "$item"; then
echo "Wrong entry, try again"
continue
fi
[ $item = "quit" ] && exit 0
echo
echo "You have selected: $item"
f_$item # Calling the function
echo
done
exit 0
Executing:
$ ./sel.sh
1) Add
2) Delete
3) Update
4) quit
Your Menu ? 1
You have selected: Add
Inside Add Function
Your Menu ? 2
You have selected: Delete
Inside Delete Function
Your Menu ? 3
You have selected: Update
Inside Update Function
Your Menu ? 5
Wrong entry, try again
Your Menu ? 4
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