ALIAS(1)                   POSIX Programmer's Manual                  ALIAS(1)



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

NAME
       alias -- define or display aliases

SYNOPSIS
       alias [alias-name[=string]...]

DESCRIPTION
       The alias utility shall create or redefine alias definitions or write
       the values of existing alias definitions to standard output. An alias
       definition provides a string value that shall replace a command name
       when it is encountered; see Section 2.3.1, Alias Substitution.

       An alias definition shall affect the current shell execution
       environment and the execution environments of the subshells of the
       current shell. When used as specified by this volume of POSIX.1-2017,
       the alias definition shall not affect the parent process of the current
       shell nor any utility environment invoked by the shell; see Section
       2.12, Shell Execution Environment.

OPTIONS
       None.

OPERANDS
       The following operands shall be supported:

       alias-name
                 Write the alias definition to standard output.

       alias-name=string
                 Assign the value of string to the alias alias-name.

       If no operands are given, all alias definitions shall be written to
       standard output.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of
       alias:

       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
       The format for displaying aliases (when no operands or only name
       operands are specified) shall be:


           "%s=%s\n", name, value

       The value string shall be written with appropriate quoting so that it
       is suitable for reinput to the shell. See the description of shell
       quoting in Section 2.2, Quoting.

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 name operands specified did not have an alias
             definition, or an error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
        1. Create a short alias for a commonly used ls command:


               alias lf="ls -CF"

        2. Create a simple ``redo'' command to repeat previous entries in the
           command history file:


               alias r='fc -s'

        3. Use 1K units for du:


               alias du=du\ -k

        4. Set up nohup so that it can deal with an argument that is itself an
           alias name:


               alias nohup="nohup "

RATIONALE
       The alias description is based on 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.

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

       Historical versions of the KornShell have allowed aliases to be
       exported to scripts that are invoked by the same shell. This is
       triggered by the alias -x flag; it is allowed by this volume of
       POSIX.1-2017 only when an explicit extension such as -x is used. The
       standard developers considered that aliases were of use primarily to
       interactive users and that they should normally not affect shell
       scripts called by those users; functions are available to such scripts.

       Historical versions of the KornShell had not written aliases in a
       quoted manner suitable for reentry to the shell, but this volume of
       POSIX.1-2017 has made this a requirement for all similar output.
       Therefore, consistency was chosen over this detail of historical
       practice.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.9.5, Function Definition Command

       The Base Definitions volume of POSIX.1-2017, Chapter 8, Environment
       Variables

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                             ALIAS(1)
