The following environment variables are supported:
This variable is used to determine the maximum length of the command history list. If this variable is not present, the default length is 128.
This variable is used to determine the pathname of the user's home directory, where a .mdbrc file may reside. If this variable is not present, no .mdbrc processing will occur.
This variable is used to determine the pathname of the shell used to process shell escapes requested using the ! meta-character. If this variable is not present, /bin/sh is used.