Unable to Open Terminal Window

Question

Hello,
I am trying to do research on how to fix my current problem of not being able to open my terminal window.  When attempting to do so I get the following error message:
You are unauthorized to run this application.
The administrator has set your shell to an illegal value.
I looked at some previous posts and some people said download iterm2 and put the following command: sudo chsh -s /bin/bash my_username.  After this enter password and it should be fixed.  However when doing that I get the following response: SC is not in the sudoers file.  This incident will be reported.
Couple of things, firstly SC (which is me) is the administrator to this computer (this is my computer and there are no other users on it). 
Either way can anyone give some suggestions on how to solve this problem so that I am able to open the terminal window.
Much thanks in advance for anyones assistance.
Sami

Answer 1

Create a new administrator account in which to change your shell and also fix the sudoers file, which is apparently corrupt. It should have the following content:
# sudoers file.
# This file MUST be edited with the 'visudo' command as root.
# Failure to use 'visudo' may result in syntax or file permission errors
# that prevent sudo from running.
# See the sudoers man page for the details on how to write a sudoers file.
# Host alias specification
# User alias specification
# Cmnd alias specification
# Defaults specification
Defaults          env_reset
Defaults          env_keep += "BLOCKSIZE"
Defaults          env_keep += "COLORFGBG COLORTERM"
Defaults          env_keep += "__CF_USER_TEXT_ENCODING"
Defaults          env_keep += "CHARSET LANG LANGUAGE LC_ALL LC_COLLATE LC_CTYPE"
Defaults          env_keep += "LC_MESSAGES LC_MONETARY LC_NUMERIC LC_TIME"
Defaults          env_keep += "LINES COLUMNS"
Defaults          env_keep += "LSCOLORS"
Defaults          env_keep += "SSH_AUTH_SOCK"
Defaults          env_keep += "TZ"
Defaults          env_keep += "DISPLAY XAUTHORIZATION XAUTHORITY"
Defaults          env_keep += "EDITOR VISUAL"
Defaults          env_keep += "HOME MAIL"
# Runas alias specification
# User privilege specification
root          ALL=(ALL) ALL
%admin          ALL=(ALL) ALL
# Uncomment to allow people in group wheel to run all commands
# %wheel          ALL=(ALL) ALL
# Same thing without a password
# %wheel          ALL=(ALL) NOPASSWD: ALL
# Samples
# %users  ALL=/sbin/mount /cdrom,/sbin/umount /cdrom
# %users  localhost=/sbin/shutdown -h now