[Wylug-help] bash help

[Smylers]

Dan Chicot writes:

> 1   #! /bin/bash
> 2   alias pp="perl"
> 3   type pp
> 4   pp
>
> pp is aliased to `perl'
> ./script.sh: line 4: pp: command not found
>
> i.e why can type determin what pp yet the shell can't?

bash(1), under 'ALIASES', says:

  Aliases  are not expanded when the shell is not interactive, unless
  the expand_aliases shell option is set using shopt.

So if you insert this before line 4 then the pp will be found:

  shopt -s expand_aliases

That's possibly yet another reason why in general it makes more sense to
use functions rather than aliases.

It doesn't however explain why type gives the output it does; I'd
suggest that's a bug, and that in a non-interactive shell when
expand_aliases is unset type should ignore aliases.

> And why does
> source script.sh
> work ok?

Because source doesn't invoke a new shell process to run the script, but
acts as though the script's contents had been typed into the current
shell, which is interactive, and therefore expands aliases.

Smylers