ALIAS(P) POSIX Programmer's Manual ALIAS(P)NAMEalias - define or display aliases
SYNOPSISalias [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 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 IEEE Std 1003.1-2001,
the alias definition shall not affect the parent process of the current
shell nor any utility environment invoked by the shell; see Shell Exe‐
cution 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
IEEE Std 1003.1-2001, 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).
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 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 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 defini‐
tion, or an error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
1. Change ls to give a columnated, more annotated output:
alias ls="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 fea‐
tures in this volume of IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001 only when an explicit extension such as -x is
used. The standard developers considered that aliases were of use pri‐
marily 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
IEEE Std 1003.1-2001 has made this a requirement for all similar out‐
put. Therefore, consistency with this volume of IEEE Std 1003.1-2001
was chosen over this detail of historical practice.
FUTURE DIRECTIONS
None.
SEE ALSO
Function Definition Command
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 ALIAS(P)
