Chapter 8, Problem 8.20HW

Use execve to write a program called my1s whose behavior is identical to the /bin/ is program. Your program should accept the same command-line arguments, interpret the identical environment variables, and produce the identical output.

  The 1s program gets the width of the screen from the COLUMNS environment variable. If COLUMNS is Unset, then 1s assumes that the screen is 80 columns wide. Thus, you can check your handling of the environment variables by setting the COLUMNS environment to something less than 80:

linux> setenv COLUMNS

linux> ./my1s

.

. //Output is 40 columns wide

.

linux> unsetenv COLUMNS

linux> ./my1s

.

 //Output is now 80 columns wide

.