UNIX for Dummies Questions & Answers

Hi again

I have the follwing - cat ~/ABCFILE | grep "$SYSTEM" | grep "$USERNAME"

What I'm looking to do is have the variable for $SYSTEM determined by the user making a selection from a numbered list. So, input 1 would be system ABC etc.

I'm very puzzled as to how to go about this?

Any advice at all would be hugely appreciated

Regards
Kip

whoami gives you the username of the person logged on (or sudo'ed into the account). Most shells have the USER environment variable but sudo will usually unset it. whoami works always.

Code:

USERNAME=$(whoami)
# in bash
echo -n "enter a system name: "
# in ksh
echo "enter a system name: \c"

read SYSTEM
grep ~/ABCFILE "$SYSTEM"  | grep "$USERNAME"

Is that what you are asking?

If you have ksh use a select loop. It generates a simple numbered menu out of a list that you must supply. It uses the same syntax as a for loop.

Code:

select myvar [in <list>]
do
  <whatever based on value of $myvar>
done

If you omit 'in <list>' it will default to using "$@" (quoted command line arguments)

This command displays the PS3 prompt for a reply. So set that to something meaningful before running the select command.


so if you did:

Code:

PS3="Select the number of your system: "

select system in ABC DEF GHI
do 
    cat ~/ABCFILE | grep "$system" | grep "$USERNAME"
    break
done

Your user will see a menu and prompt as follows:

1) ABC
2) DEF
3) GHI

Select the number of your system:

You need the 'break' in there in order to exit the select loop in an orderly fashion. Otherwise select will go on forever unless you issues a <Ctrl>D.

I have implied but not said until now that when your user selects a number the corresponding menu item will be placed in the variable 'system'. The actual number will be placed in the built-in variable 'REPLY', in case you want to make use of that. So if the user selects '2' then "$system" = "DEF" and $REPLY = 2.

Lastly, you can build a dynamic list, more or less. I've used select lists based upon files in a directory that look something like this:

Code:

select myfile in $(ls -1 /mydir/*)
do
  cat $myfile  # simplistic, but whatever you need to do to the file goes here
  break
done

Many thanks for all the help, its now working a treat.