Re: make aliases work inside the function? (using a preprocessor?)

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Wed, 4 May 2016 13:46:32 +0000
Marc Chantreux <khatar@xxxxxxxxx> wrote:
> sometimes i really need aliases.
> sometimes aliases seems to work inside functions.
>
> sometimes it works, sometimes it doesn't.

The probably is likely to be order dependence.  If you've defined an
alias, it's then available for expansion at the start of the command
line *even* if that word is defining a function.

This is explained in the FAQ (2.3; this is a long entry,
unsurprisingly).

pws


There is one other serious problem with aliases: consider
  
    alias l='/bin/ls -F'
    l() { /bin/ls -la "$@" | more }
  
  `l' in the function definition is in command position and is expanded
  as an alias, defining `/bin/ls' and `-F' as functions which call
  `/bin/ls', which gets a bit recursive.  This can be avoided if you use
  `function' to define a function, which doesn't expand aliases.  It is
  possible to argue for extra warnings somewhere in this mess.

One workaround for this is to use the "function" keyword instead:
  
    alias l='/bin/ls -F'
    function l { /bin/ls -la "$@" | more }
  
  The `l' after `function' is not expanded.  Note you don't need
  the `()' in this case, although it's harmless.

You need to be careful if you are defining a function with multiple
  names; most people don't need to do this, so it's an unusual problem,
  but in case you do you should be aware that in versions of the shell
  before 5.1 names after the first were expanded:
  
    function a b c { ... }
  
  Here, `b' and `c', but not `a', have aliases expanded.
  This oddity was fixed in version 5.1.

The rest of this item assumes you use the (more common,
  but equivalent) `()' definitions.

Bart Schaefer's rule is:  Define first those aliases you expect to
  use in the body of a function, but define the function first if the
  alias has the same name as the function.

If you aware of the problem, you can always escape part or all of the
  name of the function:
  
     'l'() { /bin/ls -la "$@" | more }
  
  Adding the quotes has no effect on the function definition, but
  suppresses alias expansion for the function name.  Hence this is
  guaranteed to be safe---unless you are in the habit of defining
  aliases for expressions such as 'l', which is valid, but probably
  confusing.