Как да деактивирам променлива env на OS X?

Работя върху правило за makefile и искам да деинсталирам променливата на средата MAKEFILES, преди да извикам make отново рекурсивно. На други BSD системи го правя така:

env -u MAKEFLAGS $(MAKE) $(SUBDIR_ARGS)

На Linux го правя така:

env --unset=MAKEFLAGS $(MAKE) $(SUBDIR_ARGS)

Въпреки това нито един от двата стила не работи на Macintosh OS X Mavericks, въпреки че бих очаквал BSD стилът, използван другаде, да работи.

Грешката, която получавам при извикването на BSD стил е:

env: illegal option -- u

Как мога да дезадам променлива на средата, преди да извикам команда в OS X и защо BSD стилът, използван другаде, не работи?

Ето man страницата на Mac за env:

ENV(1)                    BSD General Commands Manual                   ENV(1)

NAME
     env -- set and print environment

SYNOPSIS
     env [-i] [name=value ...] [utility [argument ...]]

DESCRIPTION
     env executes utility after modifying the environment as specified on the command line.  The option name=value specifies an environmental variable, name, with a value of value.  The option `-i' causes env to completely ignore the environment it inherits.

     If no utility is specified, env prints out the names and values of the variables in the environment, with one name=value pair per line.

DIAGNOSTICS
     If the utility is invoked, the exit status of env shall be the exit status of utility; otherwise, the env utility exits with one of the following values:

     0       The env utility completed successfully

     1-125   An error occurred in the env utility.

     126     The utility specified by utility was found, but could not be invoked.

     127     The utility specified by utility could not be found.

COMPATIBILITY
     The historic - option has been deprecated but is still supported in this implementation.

SEE ALSO
     execvp(3), environ(7)

STANDARDS
     The env utility conforms to IEEE Std 1003.2-1992 (``POSIX.2'').

BUGS
     env doesn't handle commands with equal (``='') signs in their names, for obvious reasons.

BSD                             August 27, 1993                            BSD

macos environment-variables porting
person WilliamKF    schedule 25.03.2014    source източник

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Използвайте командата unset. От страниците на ръководството:

unset

Remove variable or function names - the opposite of set.

Syntax
  unset [-fv] [name ...]    

  Key
   -v   Each name refers to a shell variable.(default)

   -f   Each name refers to a shell function, and the function definition is removed. 

  Example

$ unset myvariable

Each unset variable or function is removed from the environment passed to subsequent commands. If any of RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special properties, even if they are subsequently reset.

The exit status is true unless a name is readonly. It is not an error for nothing to be unset.

unset is a bash built in command.

"Look Dave, I can see you're really upset about this" ~ HAL (Space 2001)
person SevenBits    schedule 25.03.2014