This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
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implemented on Linux.
alias — define or display aliases
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.1‐2008, 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
The following operands shall be supported:
- Write the alias definition to standard output.
Assign the value of string to the alias alias-name.
If no operands are given, all alias definitions shall be written to standard
The following environment variables shall affect the execution of alias
- 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.)
- If set to a non-empty string value, override the values of all the other
- 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).
Determine the locale that should be used to affect the format and contents
of diagnostic messages written to standard error.
- Determine the location of message catalogs for the processing of
The format for displaying aliases (when no operands or only name
are specified) shall be:
string shall be written with appropriate quoting so that it is
suitable for reinput to the shell. See the description of shell quoting in
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
- Successful completion.
- One of the name operands specified did not have an alias
definition, or an error occurred.
The following sections are informative.
- Create a short alias for a commonly used ls command:
- Create a simple ``redo'' command to repeat previous entries in the command
- Use 1K units for du:
- Set up nohup so that it can deal with an argument that is itself an
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.1‐2008, such as command line editing.
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
flag; it is allowed by this volume of
POSIX.1‐2008 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.1‐2008 has
made this a requirement for all similar output. Therefore, consistency was
chosen over this detail of historical practice.
, Function Definition Command
The Base Definitions volume of POSIX.1‐2008, Chapter 8
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 .
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