[slubman@slubman : ~/tmp]
$ cat tmp.sh
#! /usr/bin/env bash

case `whoami` in
  oussama|toto)
  ;;
  *) exit;;
esac

echo "coucou"


[slubman@slubman : ~/tmp]
$ ./tmp.sh

[slubman@slubman : ~/tmp]
$ cat tmp.sh
#! /usr/bin/env bash

case `whoami` in
  slubman|toto)
  ;;
  *) exit;;
esac

echo "coucou"


[slubman@slubman : ~/tmp]
$ ./tmp.sh
coucou