default values

default values

[Emanuel Berg]

Is there a C-like "... ? ... : ... ;" syntax or
otherwise standard or conventional way to assign
default values to sometimes-not-submitted parameters?

I have found many ways to do it and I can't tell if
one is better than the other.

For example, like this:

    biggest-files () {
        local num_files=10
        local where=./

        if [ $1 ]; then num_files=$1; fi
        if [ $2 ]; then     where=$2; fi

        du -ahS $where | sort -hr | head -n $num_files
    }

How is this supposed to look?

-- 
underground experts united .... http://user.it.uu.se/~embe8573
Emacs Gnus Blogomatic ......... http://user.it.uu.se/~embe8573/blogomatic
                   - so far: 20 Blogomatic articles -                   

Re: default values

[Bart Schaefer]

On Mar 30,  8:12pm, Emanuel Berg wrote:
}
} Is there a C-like "... ? ... : ... ;" syntax or
} otherwise standard or conventional way to assign
} default values to sometimes-not-submitted parameters?

In math context you can actually use ternary syntax:

    $(( x ? y : z ))

But I think you're actually looking for this:

${NAME-WORD}
${NAME:-WORD}
     If NAME is set, or in the second form is non-null, then substitute
     its value; otherwise substitute WORD.  In the second form NAME may
     be omitted, in which case WORD is always substituted.

So e.g.

    local num_files=${1:-10}
    local where=${2:-./}

Re: default values

[Emanuel Berg]

Bart Schaefer <schaefer@brasslantern.com> writes:

> ${NAME-WORD} ${NAME:-WORD} If NAME is set, or in the
> second form is non-null, then substitute its value;
> otherwise substitute WORD. In the second form NAME may
> be omitted, in which case WORD is always substituted.
>
> So e.g.
>
>     local num_files=${1:-10} local where=${2:-./}

Excellent, thanks!

-- 
underground experts united .... http://user.it.uu.se/~embe8573
Emacs Gnus Blogomatic ......... http://user.it.uu.se/~embe8573/blogomatic
                   - so far: 20 Blogomatic articles -