Simplify subject

subjects/ztail/README.md

@@ -2,18 +2,10 @@
 
 ### Instructions
 
-Write a program called `ztail` that has the same behaviour as the system command `tail`, but which takes at least one file as argument.
+Write a program that behaves like a simplified `tail` command but which takes at least one file as argument.
 
-- The only option to be handled is `-c`. This option will be used in all tests.
+- The only option to be handled is `-c`. This option will be used in all the tests as the first argument, with positive values.
 
-- For this program the "os" package can be used.
+- For this program the `os` package can be used.
 
-- For the program to pass the tests the convention for the return code of program in Unix systems should be followed.
-
-- Handle the errors and output the same error messages as `tail`.
-
-- For more information consult the man page for `tail`.
-
-### Note:
-
-This program is gonna be tested against `tail`, be sure to check all the different error messages with different permutations of the arguments.
+- Handle the errors by returning a non-zero exit status.