[SOLVED] Redirections changes "get-alias" command return code in powershell

Redirections changes "get-alias" command return code in powershell

I want test if an alias exists with the following code :

if( (get-alias ls) ) {
    echo "=> Alias ls already exists."
} else {
    echo "=> Alias ls does not exist."
}

When run, it says :


CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Alias           ls -> Get-ChildItem


=> Alias ls already exits.

I tried to redirect the output of the command to $null :

if( (get-alias ls >$null) ) {
    echo "=> Alias ls already exits."
} else {
    echo "=> Alias ls does not exist."
}

I expected this output when run :

=> Alias ls already exists.

But the outcome of the code snippet somehow changed :

=> Alias ls does not exist.

If I redirect after the first set of parenthesis, I also get :

=> Alias ls does not exist.

Why does redirection interfere with the result?

Solution

If tests whether or not there's output, not the result code $? of the command. You can combine two statements with $( ).

echo hi > foo

if (dir foo > $null) <# no result #> { 'yes' }


if ($(dir foo > $null; $?)) { 'yes' }

yes