I am trying to use a function in my script. I'm not quite sure how to complete it. This is my assignment:

The first version of hw12.sh should display the usage message "usage: $0 argument", "Enter one or more arguments." when no arguments are on the command line.

$ hw12.sh
usage: hw12.sh argument
Enter one or more arguments.

- The second version of hw12.sh should display the message "There were $# arguments on the command line" if there were 1 or more arguments on the command line. Here is an example.

$ hw12.sh abc 123
There were 2 arguments on the command line.

- The final version of hw12.sh has the following change. Display the usage message from a function. Here is an example.

$ hw12.sh hello hw12.sh
There were 2 arguments on the command line.
$ hw12.sh
usage: hw12.sh argument
Enter one or more arguments.

This is my code that wrote but it says i have a syntax error any help would be appreciated. Thank you

if [ $# -eq 0 ]
then echo "usage: $0 argument"
     echo "Enter 1 or more arguments"
     else "There were $# arguments on the command line"
     exit 1
fi

What error are you seeing? Please post the error message.

As you can see i must use "Usage:" as my function so i changed my code to fullfill the assignment but it doesn't seem its working correctly. I'm new to unix to the whole using function is confusing. This is the new code im trying in my script:

#Vitaly Kuzyanov
usage()
{
 [ $# -eq 0 ]
 echo "usage: $0 argument"
}
if usage
     then echo "Enter 1 or more arguments"
     else "There were $# arguments on the command line"
     exit 1
fi

You are missing the echo in the else branch.
On top, a function will always have a complete set of parameters of its own, so, in your case, usage will always have zero parameters, regardless of how many parameters your script has gotten. Do input error testing in the body of the script, then call respective error handlers/functions.