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Old 11-29-2011, 12:13 PM   #1
SecureScript
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If Statement for User Status


I am writing a bash script to let the user check if a specific username is currently logged in. However my script returns that "the username is logged in" even if they are not. I figure it has to be a problem with my If statement. Here is my code:

#========================================================
#!/bin/bash

clear
tput cup 2 1; echo "Enter username: "
tput cup 2 25;
read choice || continue

userchoice=`who | grep $choice | cut -d' ' -f1`
tput cup 5 14; echo "User $userchoice is logged on."

if [ $userchoice = 0 ]
then
tput cup 5 14; echo "User $userchoice is not logged on."
fi

exit 0
#============================================================

Any help is appreciated. Thanks!
 
Old 11-29-2011, 12:27 PM   #2
kbscores
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It will always print that User is logged in because it is not in an if statement at all

you need to do

Code:
if [ $userchoice = 0 ]
then tput cup 5 14; echo "User $userchoice is not logged on."
else tput cup 5 14; echo "User $userchoice is logged on."
fi
 
Old 11-29-2011, 12:47 PM   #3
SecureScript
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Ok thanks kbscores, that is the correct If statement, however when I run it I get an error "Too many arguments" on the line starting with the If statement:

Code:
if [ $userchoice = 0]
 
Old 11-29-2011, 01:02 PM   #4
kbscores
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Most likely it is returning several instances of a single user - for instance if you had three different shell windows open the who cut statement and your username is jbob it would return:

jbob
jbob
jbob

Since you aren't saving it to an array it is going to give an error. Try declaring variable first using:
Code:
declare -a userchoice
and then when you reference it use first instance of name so in if statement it would look like:
Code:
if [ $userchoice[0] = 0 ]
I'm thinking you may want to use null instead of zero as well.
 
Old 11-29-2011, 01:42 PM   #5
SecureScript
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I did declare the array with null values as you said, but it still comes back saying user is logged in every time.

I'm thinking though, I already have userchoice declared (towards the top of the script):

Code:
userchoice=`who | grep $choice | cut -d' ' -f1`
Could that be conflicting with the declare -a userchoice that you suggested?
 
Old 11-29-2011, 01:49 PM   #6
kbscores
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actually now that I think about it since you only need one use a sort -u

it is sort of long winded but it'll work.

I just wrote out script - I wouldnt use variable at all if you use sort.
 
Old 11-29-2011, 01:53 PM   #7
kbscores
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this is what i did and it worked:

Code:
#!/bin/bash

echo "Enter name:"
read choice || continue 
if ["$(who |grep $choice | cut -d ' ' -f1 |sort -u)" == "$choice" ]
then echo "User $choice is online"
else echo "User $choice is not online"
fi
exit 0
 
Old 11-29-2011, 06:54 PM   #8
grail
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As we are using bash, why not just keep it simple:
Code:
if who | grep -q "$choice"
then
    echo "User $choice is online"
else
    echo "User $choice is offline"
fi
 
Old 11-30-2011, 08:44 AM   #9
David the H.
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Quote:
Originally Posted by SecureScript View Post
Ok thanks kbscores, that is the correct If statement, however when I run it I get an error "Too many arguments" on the line starting with the If statement:

Code:
if [ $userchoice = 0]
There needs to be a space before the final bracket. Remember, [ is a command, and all the pieces following the initial bracket are arguments to that command which need to be separated by whitespace in order for the shell to parse it correctly. In this case "0]" is treated as a single argument, meaning it can't find the closing bracket and thinks that everything following it is also part of the test.

In addition, always quote your variable substitutions, particularly inside [..]. A variable containing multiple words would otherwise be seen as multiple arguments.

More on argument processing here:
http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes


Finally, you can avoid most of these problems in bash by using the new [[ test keyword instead.

But in fact, numeric comparisons like this are better done with the ((..)) arithmetic evaluation brackets.

Code:
if (( userchoice == 0 )) ; then
 
  


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