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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
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.1‐2008, 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 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.1‐2008, 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
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.1‐2008, 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.1‐2008 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.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.9.5, Function Definition Command
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables
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 .
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