The s6-envdir program

s6-envdir changes its environment, then executes into another program.

Interface

     s6-envdir [ -I | -i ] [ -n ] [ -f ] [ -c nullis ] dir prog...

s6-envdir reads files in dir. For every file f in dir, that does not begin with a dot and does not contain the '=' character:
If f is empty, remove a variable named f from the environment, if any.
Else add a variable named f to the environment (or replace f if it already exists) with the first line of the contents of file f as value. Spaces and tabs at the end of this line are removed; null characters in this line are changed to newlines in the environment variable.

-i : strict. If dir does not exist, exit 111 with an error message. This is the default.
-I : loose. If dir does not exit, exec into prog without modifying the environment first.
-f : verbatim mode. All the file is given as the value of the environment variable, including newlines (except the last one if the -n option is not given). Null characters are still translated.
-n : do not chomp. If the -f option is given and the file ends with a newline, keep that last newline in the value. If the -f option is not given, keep the trailing blanks at the end of the first line (but not the ending newline).
-c nullis : replace null characters with the first character of nullis instead of a newline.

s6-envdir without options behaves exactly like envdir.