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#1
03-28-2008
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Loop Mania
hello all, here is my first post since i am in need of figuring out what my exact problem is. Here is what i'm trying to do:
run a script to check and see if a user exists on the system and if not sends an error message and says "try again or type exit to quit". If the user types exit the program will terminate. If the user does exist on the system (all users are located in /etc/passwd), the program will finger the user and returns it the information to the screen. Once the successful user was found the program will exit normally. If the user is not found the program will loop until the user either types exit or successfully enters a user name. Code:
#!/bin/bash
error_fn()
{
echo user entered $username
echo try again or type exit to quit
read answer
case $answer in
exit|Exit|EXIT) exit 20
;;
*)
echo please enter a user to find
read $usertry
while grep $usertry /etc/passwd
do
finger $usertry
exit 1
done
esac
}
echo "HELLO AND WELCOME TO YOUR USER SEARCHING UTILITY"
echo please enter the name of the user you wish to find
read username
echo "you entered $username"
if grep $username /etc/passwd
then finger $username
else error_fn
fi
Script: 1st part) it will successfully grep users that are in /etc/passwd and finger them. 2nd part) However, if i type in a user that is not there and get taken to the error function that starts, it will ask me to enter exit or try another username entry. But when a user that exists is entered it will repeat the line and not finger and exit. 3rd part) last but not least when i continually enter in a username that doesnt exist it doesnt loop. 
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#2
03-29-2008
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If I were you I would take away the interactive features, but then you would end up with basically just grep anyway.
You really really must quote user-supplied input variables. Somebody could type `rm -rf $HOME` with the backticks at your prompt and then blame you for the consequences. You are planning to not ever have a user named "exit" then? Perhaps empty input should be used to quit, instead. You have the grep function twice. I would refactor so the grepping is in a function and the flow control is the main body of the script. The actual problem is that you have a dollar sign in front of the variable in the read inside the function. Hope this helps.
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#3
03-29-2008
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This will give you the desired output:
Code:
#!/bin/bash
error_fn () {
echo " enter a valid username, or type exit to quit"
read name
if grep "$name" /etc/passwd
then finger "$name"
exit 0
else
if [ "$name" = exit -o "$name" = Exit -o "$name" = EXIT ]
then
exit 20
fi
fi
}
echo " enter user or type exit to quit"
read answer
case "$answer" in
exit|Exit|EXIT) exit 20
;;
*) while true
do
if grep "$answer" /etc/passwd
then
finger "$answer"
break
else
error_fn
continue
fi
done
;;
esac
Last edited by rubin; 03-30-2008 at 07:23 PM. Reason: added quoting & replaced exit 0 with break inside the loop ( thanks to era for suggesting )
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#4
03-29-2008
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I have successfully run the first portion of this script and it has taken me to the error function but here is where i get stuck. The case statement works correctly and will exit if the user has entered any of the exit words. If they enter a user name to search for that exists the script should display the user searched for, finger them, and exit to command prompt. If they enter a user that doesn't exist, they should be caught at the TRY AGAIN loop until they enter a proper username or type exit.
Anyhow, here is the updated code that i worked on this morning: Code:
#!/bin/bash
error_fn()
{
echo User Not Found please try again type exit or Q-q to quit
read answer
case $answer in
q|Q|exit|Exit|EXIT) exit 20
;;
*)
while [ $? -gt 0 ] ;
do
echo "User not found please try again:"
done
esac
}
echo please enter the name of the user you wish to find:
read username
echo "you entered $username"
if cat /etc/passwd| grep $username
then finger $username
else error_fn
fi
So im not sure which loop to use in the function while? or until?
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#6
03-29-2008
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Solved Thank You!!!
WOOOT Thank you soo much problem solved and the loop is in place.
I need to get this concept of thinking simple because i tend to easily get lost in syntax and trying to figure out which loop to use. Again, thanks for the help and i'll be posting some more puzzlers soon. 
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#7
03-29-2008
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I would use a while with a non-local exit. Like this:
Code:
while true do stuff case $stuff matches) do your things; break ;; esac done I'll say it again: where you have $variable, you should have "$variable", throughout. There are good FAQ sheets about shell quoting on the net -- find them and read them if you ever write anything which involves user input.
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