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       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       unalias — remove alias definitions

SYNOPSIS

       unalias alias-name...

       unalias −a

DESCRIPTION

       The unalias utility shall remove the definition for each alias name specified. See Section
       2.3.1, Alias Substitution.  The aliases shall be removed from the current shell  execution
       environment; see Section 2.12, Shell Execution Environment.

OPTIONS

       The  unalias utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section
       12.2, Utility Syntax Guidelines.

       The following option shall be supported:

       −a        Remove all alias definitions from the current shell execution environment.

OPERANDS

       The following operand shall be supported:

       alias-name
                 The name of an alias to be removed.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of unalias:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.   (See   the   Base  Definitions  volume  of  POSIX.1‐2008,  Section  8.2,
                 Internationalization  Variables  for  the  precedence  of   internationalization
                 variables used to determine the values of locale categories.)

       LC_ALL    If  set  to  a  non-empty  string  value,  override  the values of all the other
                 internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of sequences of bytes of  text  data
                 as  characters  (for example, single-byte as opposed to multi-byte characters in
                 arguments).

       LC_MESSAGES
                 Determine the locale that should be used to affect the format  and  contents  of
                 diagnostic messages written to standard error.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       Not used.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0    Successful completion.

       >0    One of the alias-name operands specified did not represent a valid alias definition,
             or an error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       Since unalias affects the current shell execution environment, it is generally provided as
       a shell regular built-in.

EXAMPLES

       None.

RATIONALE

       The unalias description is based on that from historical KornShell implementations.  Known
       differences exist between that and the C shell. The KornShell version was  adopted  to  be
       consistent  with  all the other KornShell features in this volume of POSIX.1‐2008, such as
       command line editing.

       The −a option is the equivalent of the unalias * form of the C shell and  is  provided  to
       address  security  concerns  about  unknown aliases entering the environment of a user (or
       application) through the allowable implementation-defined predefined alias route or  as  a
       result  of  an  ENV file. (Although unalias could be used to simplify the ``secure'' shell
       script shown in the command rationale, it does not obviate the need to quote  all  command
       names.  An  initial  call to unalias −a would have to be quoted in case there was an alias
       for unalias.)

FUTURE DIRECTIONS

       None.

SEE ALSO

       Chapter 2, Shell Command Language, alias

       The Base Definitions volume of POSIX.1‐2008, Chapter  8,  Environment  Variables,  Section
       12.2, Utility Syntax Guidelines

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .