SYNOPSIS
       unset [-fv] name ...

DESCRIPTION
       Each variable or function specified by name shall be unset.

       If  -v is specified, name refers to a variable name and the shell shall
       unset it and remove it from the environment. Read-only variables cannot
       be unset.

       If -f is specified, name refers to a function and the shell shall unset
       the function definition.

       If neither -f nor -v is specified, name refers  to  a  variable;  if  a
       variable by that name does not exist, it is unspecified whether a func-
       tion by that name, if any, shall be unset.

       Unsetting a variable or function that was not previously set shall  not
       be considered an error and does not cause the shell to abort.

       The unset special built-in shall support the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       Note that:


              VARIABLE=

       is not equivalent to an unset of VARIABLE; in the example, VARIABLE  is
       set  to "" . Also, the variables that can be unset should not be misin-
       terpreted to include the special parameters (see Special Parameters ).

OPTIONS
       See the DESCRIPTION.

OPERANDS
       See the DESCRIPTION.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       None.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

       >0     At least one name could not be unset.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
       Unset VISUAL variable:


              unset -v VISUAL

       Unset the functions foo and bar:


              unset -f foo bar

RATIONALE
       Consideration was given to omitting  the  -f  option  in  favor  of  an
       unfunction  utility, but the standard developers decided to retain his-
       torical practice.

       The -v option was introduced because System  V  historically  used  one
       name space for both variables and functions. When unset is used without
       options, System V historically unset either a function or  a  variable,
       and  there  was  no  confusion about which one was intended. A portable
       POSIX application can use unset without an option to unset a  variable,
       but not a function; the -f option must be used.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Special Built-In Utilities

COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .