Why is Bash automatically inserting `--color=auto` in `ls` command used in function

Question

I have this setup file:

function latest { 
    count=${1:-5} ; 
    echo "Just changed"
    ls -lrtd * | tail -$count ; 
}

I call it:

. setup

Then I ask bash if the latest function is defined:

>type latest
latest is a function
latest () 
{ 
    count=${1:-5};
    echo "Just changed";
    ls --color=auto -lrtd * | tail -$count
}

Just changed is an arbitrary string that I used to make sure I was not looking at a definition of latest from another file.

And the question is: why is Bash adding the --color=auto to the ls command (where it is of no use since the output is piped anyway). And yes, on my shell ls is aliased to ls --color=auto, and if I remove the alias this doesn't happen. But I thought aliases where not used in functions and in any case this substitution happened at function definition time?

Answer 1

You've observed documented behavior; in the Alias section of the bash manual:

Aliases are expanded when a function definition is read, not when the function is executed, because a function definition is itself a command.

Answer 2

Jeff is correct above. To see the aliases defined in your shell, type "alias" at the prompt.

Example:

[USERID ~] $ alias
alias l.='ls -d .* --color=auto'
alias ll='ls -ahlF'
alias ls='ls --color=auto'
alias vi='vim'
[USERID ~] $

To avoid the alias in your script, you would need to either unalias the "ls" command or call it directly. To find the location of "ls", use the type shell builtin:

[USERID ~] $ type -P ls
/usr/bin/ls

You could put that in a variable and call "ls" using the variable:

[USERID ~] $ lsCmd=$(type -P ls)
[USERID ~] $ echo $lsCmd
/usr/bin/ls
[USERID ~] $ ls
MyAppData  MyDocuments  MyDownloads  Scripts  tmp.VOOlcGffwf  tmp.Y6IE7S2ps4
[USERID ~] $ $lsCmd
MyAppData  MyDocuments  MyDownloads  Scripts  tmp.VOOlcGffwf  tmp.Y6IE7S2ps4

In the first case, calling just "ls" gives the output in color because "ls" is aliased to "ls --color=auto" but the second case give the output without color as the alias is bypassed.