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PROLOG
       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.1‐2017, 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.1‐2017, 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.1‐2017, 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.1‐2017, 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 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .

IEEE/The Open Group                                   2017                                       UNALIAS(1POSIX)