News Group Posts

where do aliases get set for bash?

From: Floyd Davidson <floyd@ptialaska.net>
Subject: Re: Aliases
Date: 03 Dec 2002 11:34:31 -0900
References: <asi59v$sra$1@arcturus.ciril.fr>
<3dec9b6c$0$2764$afc38c87@news.optusnet.com.au>
<asicb2$85c$1@arcturus.ciril.fr> 

radilla@mines.u-nancy.fr (Giovanni Radilla) wrote:
>Thank you for your help on both of my questions.
>For this one I still don't know the answer. Here
>is the file /etc/profile:
>
>---->[BEGIN]
>
># /etc/profile -*- Mode: shell-script -*- 

  [snip]

>for i in /etc/profile.d/*.sh ; do
>    if [ -x $i ]; then
>            . $i
>    fi
>done

  [snip]

>where are the aliases?

Read the man page for bash, and do "/INVOCATION" about three
times to find the subsection which describes how bash reads
init files.

A "login" shell (as opposed to a subshell) sources /etc/profile
first, and then sources the first of these files that it can
find,

     ~/.bash_profile
     ~/.bash_login
     ~/.profile

A login shell does *not* source ~/.bashrc, and hence if you do
not have a command to source it in whichever of the above three
files you use, nothing you have in ~/.bashrc file will affect
your login shell!

Also note that aliases are _not_ inherited by subshells, hence
an alias defined in /etc/profile or in ~/.bash_profile will not
exist in a subshell (for example in an xterm running bash unless
they are all configured to be login shells).

All of this make sense and works correctly *if* your init files
are used properly.  /etc/profile should be used to set up a
system-wide bare minimum interactive shell environment.  It is
*not* the place to define aliases!  It should define environment
variables that are unique to each system (ones which a user
would not likely want to change), or which are necessary for an
interactive login to function.  Hence PATH, MANPATH, PS1, PS2,
and things like that are all that should be set there.

Each user should choose one of the three files to be sourced by
a login shell, and use it to add to or adjust what is in
/etc/profile.  Environment variables that are unique to this
user, but that will always be the same in all shells can be set
in this file, but it is actually easier to not do that.  What
*must* be in this file are any terminal configuration setup
commands which need to only be executed one time per login (and
not every time a subshell is invoked).  That would be something
like "stty erase ^H", for example.  Also commands which add to
variables, and hence should only be done once, can be put in
this file:

   PATH=~/bin:$PATH

In addition, non-interactive shells (shells used to run scripts,
for example) will source whatever file is set for BASH_ENV, so
that should be set.  And if all aliases are set in ~/.bashrc, a
command to read it should be used.

Hence ~/.bash_profile might look like this,

  stty erase ^H
  export BASH_ENV=~/.bashrc
  export PATH=~/bin:$PATH
  . ~/.bashrc

And then you can put all of your function definitions,
environment variables, and aliases into ~/.bashrc and expect to
see them correctly in any shell you invoke!

-- 
Floyd L. Davidson         <http://www.ptialaska.net/~floyd>
Ukpeagvik (Barrow, Alaska)                 floyd@barrow.com
 

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