ALIAS(1P) POSIX Programmer's Manual ALIAS(1P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
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NAMEalias — define or display aliases
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 environ‐
ment 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
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
The following environment variables shall affect the execution of
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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).
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
NLSPATH Determine the location of message catalogs for the processing
The format for displaying aliases (when no operands or only name oper‐
ands 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.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
0 Successful completion.
>0 One of the name operands specified did not have an alias defini‐
tion, or an error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
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 nohup="nohup "
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 fea‐
tures in this volume of POSIX.1‐2008, such as command line editing.
Since alias affects the current shell execution environment, it is gen‐
erally 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 trig‐
gered 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. There‐
fore, consistency was chosen over this detail of historical practice.
Section 2.9.5, Function Definition Command
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
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 Electri‐
cal 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
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IEEE/The Open Group 2013 ALIAS(1P)