script to add user to system and test if user exists

[marinestu]

Hello Team

I have a scripting question for you all...would one of you good sorts please tell me why this script does not work. I am testing the variable $test to make sure that it contains a value. If it does the user is on the system and the script ends here. If however there is no value to the variable $test then the user is added to the system.

The thing is it seems the system thinks there is always a variable to $test and thus does not add the user.

I am sure this is something simple....who wants some easy credit here ;-)

Take care guys and thanks



#!/bin/bash
# Adding and testing to see if the someuser users exists on the system
tuser=someuser
test=`grep $tuser /etc/passwd`
#echo $test

if [ -n $test ]
then
echo "User $tuser is on the system contact root"

else echo adding $tuser to system; useradd $tuser; /bin/echo password | /usr/bin/passwd bmc --stdin
fi

[Gareth Jones]

Use:

[ -n "$test" ]

or

[[ -n $test ]]

or

[[ -n "$test" ]]

The quotes cause an empty $test to expand to a null string (""), which behaves as it should:

[ -n "" ]

Without that, the empty $test expands to nothing at all, and the test becomes:

[ -n ]

i.e. it tests if "]" is a non-null string! "[" has an odd syntax. Although it is built into bash, traditionally it's an external command (see "/usr/bin/["), so the "]" is an optional part of its command line...

"[[ ... ]]" is guaranteed to be a shell built-in, and because of that is aware of $test being a shell variable (rather than only getting the expanded version on its command line), so the quotes are optional.

The "[ ... ]" syntax is for compatibility with traditional Bourne shell, POSIX prefers "[[ ... ]]" for new code.

Gareth

---------- Post added at 12:06 AM ---------- Previous post was at 12:01 AM ----------

Also note that your script will catch any match in /etc/passwd, not just user names. Try adding a user "bash" with your script for example.

[RupertPupkin]

As Gareth mentioned, you should be careful to match only the username in the first colon-delimited field of /etc/passwd, which you could do like this:

#!/bin/bash
tuser=someuser
test="$(grep ^${tuser}: /etc/passwd)"
if [ -n "${test}" ]; then
   echo "User ${tuser} is on the system, contact root"
else
   echo "Adding ${tuser} to system"
   # Do some more stuff
fi

[marinestu]

Hello Guys

Thanks for taking the time to not only show me the error of my ways but also come up with a better solution to my question.

Looking forward to getting my hands on F16

Take it easy now

Cheers