# alias

## 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.1‐2017, 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.
    


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